Sorry to post yet another TD/Q topic. I try to limit it to one per week if I can. Anyway, I'm fixing/installing AC into my 86GT/86 4Cyl.

The car itself is an 86 bumperpad 4cyl with the V5 AC system. The engine, however, came from an 86GT. It is a 3.4l with a lot of mods/etc, but we'll just pretend it's a 2.8l for our purposes.

I have bought and installed a Harrison HR6 Reman by Four Seasons with new switches, a new Receiver/Dryer, O-rings, some lines, and my evaporator. The system is holding vacuum and what pressure can be generated without the compressor kicking on.

That's the problem...the compressor won't kick on. I installed new high and low pressure cut-out switches. Both of them are the 2 terminal kind that have "Replaced" the one terminal variety. One switch came with a connector and instructions saying to splice either wire into the high pressure switch wire, and ground the other one. The low pressure switch came with nothing, so I bought a connector and did the same thign I did with the high pressure switch...spliced one wire in, grounded the other.

So, right now, I have my high and low pressure switched installed on the compressor, both with one wire attached to the original wiring for each of them, and one wire grounded. If my reckoning is correct, when one of the switches is activated it just jumps the terminals and grounds the wiring to the chassis. Is that correct?

In a nutshell, here is what I'm asking...

1. I know the high pressure switch is normally closed, meaning the terminals are not connected and there is no wiring that is grounded by default. Does the low side operate the same way, meaning I can connect one wire to the low pressure cut-out wiring and ground the other?

2. If I have the wiring right in question 1, what do I do next? I think I am missing the clutch cycling switch. Luckily, the receiver dryer I bought has a port for one and I just happened to pull one at the junkyard 2 days ago thinking it might come in handy someday before I even knew I was going to have this problem. Do I need to run some wire back from that clutch cycling switch? If so, where to?

3. Is there any way I can bypass the clutch cycling switch just to see if the system works?

4. Where should I be looking for power to the compressor clutch? I have a 2 pin connector that plugs into the clutch on the compressor, but it can be flipped and installed the other way around so I'm not sure which way it should be installed.

Thanks so much for any help you can give...I'm dying in this heat and humidity without AC and I've already spent over 400 dollars to get this up and running...

------------------
86GT Modded 3.4l V6/Getrag with Trueleo - 210WHP
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Just wanted to mention I jumped the relay behind the air cleaner and also tried jumping the terminals on the two wire low pressure cutout connector. Still nothing...maybe I'm not getting power to the clutch? Any ideas?

For wiring diagram information check this site out: http://www.fieronews.net/fusion/downloads.php


The diagram, schmatic you are looking for is the "Air Conditioning System - Compressor Controls".

For a 4-cyl engine the wiring goes something like this: the A/C select switch supplies 12V to the Low Pressure Switch (NC). It in turns provides power to the High Pressure Switch (NC), that in turns provides power to the AC Compressor Control Relay. Ground for the relay is provided by the ECM. The Low Pressure Switch also provides over ride power to the coolant fan.

Hope this helps? Sorry I cannot attached the wiring diagrams.

okay here is what I would do. First off I dont know about that compressor but I would not think the low pressure switch would be on the compressor? I dont know that though. Most just have the low pressure switch on the dyer and one high pressure switch on the compressor. The other hole is plugged. Again, Im not familiar with your system. I would first make sure you have power getting to the relay. Jump the low pressure switch out on the dyer first. I know you said you jumped the relay on the back by the aircleaner, but did you run unhook the relay from the harness? As you said your ecm grounds the coil on the relay and if there is a problem there then the relay wont fire. I would unhook the relay and double verify which wire goes to your compressor. Jump the wires on the harness and make sure you are getting 12 volts to one of the wires on the clutch plug. You can leave the harness jumped and go down there with a meter and check both wires to ground and you should have 12 volts assuming you have the 12 volts at the terminal you jumped from on the relay. ( I think to get 12 volts on this pin you have to have the key on and the AC on, dont have to start the car). If you have 12 volts from either of the clutch plug wires to ground and dont have 12 volts between the two clutch plug wires you know one of the switches is open. You should be able to stick one of your leads on the frame of the car (or good ground) and one of them to the spade on either of the switches and get continuity. If you dont have continuity, one or both of the switches are open. I dont know if they are in series or not but if they are check them individually to see which one is not cooperating. I had a problem with my clutch relay on mine. The relay wouldnt fire, but I had voltage at the harness, I could jump the harness out and the clutch would pull in. I could bench check the relay and it worked but wouldnt work in the harness. The problem ended up being the harness. Put a new harness in and it worked like a charm. As far as the clutch plug, it doesnt matter what wires goes where, its just a coil and doesnt care as long as its got 12 volts on one side and ground on the other.

Just looked, I don't have an E terminal on either of my firewall relays. No wire going into that terminal at all on either one. NOW what?

The control circuits are significantly different between the V5 compressor and the DA6/HR6 compressor systems.

For a CCOT system (i.e. DA6/HR6 compressor) you need a pressure cycling switch, mounted on the accumulator. It closes to apply the compressor clutch when the low-side pressure is above about 32 psig and opens when that pressure drops below about 26 psig. Similarly, both switches on the head of a DA6/HR6 compressor are high pressure switches; one is normally open and closes (redundantly) to turn on the radiator fan when the high-side pressure goes above normal operating limits, the other is normally closed and opens to disengage the compressor clutch if the high-side pressure goes even higher. The pressure cycling switch in a CCOT system doubles as a low pressure cutoff switch.

The place for you to begin is to print a copy of the wiring diagram for a Fiero CCOT (V6 w/ DA6/HR6 compressor) AC system, study it until you understand it, and then duplicate it in your car.

[This message has been edited by Marvin McInnis (edited 06-10-2010).]

I had to make a choice when putting the Aurora engine in my 88 coupe that had a V5 compressor. Either use the stock A/C compressor from an Aurora that bolted right to the engine block or use the stock Fiero V5 compressor and not have to deal with changing the wiring to make it work. For fear that it would turn into a major wiring quagmire I decided to use the V5 compressor and fab the mounts. I don't know if this was the easiest way but I am much better and making mounts than running wire. I am curious to see how you work this out.

Charlie

Like mentioned above, the two A/C systems are quite different. Since your 4cyl Fiero was setup for the V5 compressor, it doesn't have the cycling switch in the accumulator/dryer. You will need to install the cycling switch (and accompanying wiring) so the compressor clutch can be cycled on and off. The cycling switch taps into the light green wire that runs from the HVAC control panel to the A/C relay. So with the DA6 / HR6 setup, that light green wire would go from the HVAC control panel to the cycling switch, then the light blue wire from the cycling switch would run back to the A/C relay.

There are two switches on the HR6 / DA6 compressor. One is a high-pressure cutoff. It interrupts the power to the compressor clutch if the pressure gets too high. It's wired into the ground wire (black) for the compressor clutch. So that black wire needs to go to the switch, and then from the switch to ground. The other switch activates the radiator fan. It grounds out the green / white wire that activates the fan relay. This is the same wire that goes to the fan switch on the engine. So you can just tap into that wire. Although, if you're using a 2-wire switch for that, the second wire will need to be grounded to the engine or chassis.

Your V6 engine wiring harness should have the wiring for the compressor switches. But you should double-check to make sure it's all intact and connected properly. However, you will need to run the wiring for the cycling switch in the accumulator / dryer.

[This message has been edited by Blacktree (edited 06-15-2010).]

If all you want to do , is getting the AC blowing cold to see if it works, First ,pull a vacuum for about 1/2 an Hour. then put in 1 -12 oz can of 134 ( the engine doesn't even have to be running for the first one) you did put ester OIL in the drier & compressor , right ? Next, jump the wires at the plug that would connect to the cycling switch at the drier, start the car, put AC on max, install another 12oz can of 134. The compressor should be running at this point because the cycling switch is jumped (bypassed). It Should be blowing cold. You can install the cycling switch with freon in the system, it won't leak out, put the plug on it. if the switch is good & you have no leaks, you can now check the pressure. It MAY cycle alot, if the cycling switch is not adjusted for 134. to slow down the cycling, turn the screw between the 2 prongs for the switch (1/2 turn counter clockwise) don't try to remove the "High pressure & low pressure switches when there is freon in the system. hope that helps ya

quote Originally posted by Lou6t4gto: Next, jump the wires at the plug that would connect to the cycling switch at the drier,

There are no wires on his car for a compressor cycling switch... This is the problem....

Charlie

Alright, I have a front harness coming with the appropriate connectors. Does anyone know if the wiring between the front compartment and my V6 wiring harness has provisions for the clutch cyclcin g switch wiring?

I guess what I'm asking is:

*FRONT COMPARTMENT WIRING* ------ *CABIN/INSIDE OF CAR WIRING* ----- *ENGINE BAY WIRING*

^^^ This is V6 with AC wiring ^^^ ^^^ This is 86 4Cyl wiring ^^^ ^^^ This is 86 V6 Wiring ^^^

The wiring in the middle that is going through the car is what I'm worried about. If the pins are all the same between 4cyl and V6 cars I'm golden, but otherwise it sounds like I will have to do some repinning. Does anyone know where to point me from here? I've tried to study wiring diagrams, I promise, and I've used the search button extensively. I'm just no good with wiring diagrams.

Bump for help...

If it was my car, here's what I'd do:
I'd get the Helms manual, look up the wiring for a V6 AC system, and then run wires from the AC cycle switch to where they're supposed to go. I wouldn't worry about what wires were already in the car -- I'd just run new wires from the switch to where they're supposed to go. I'm sure I could snake them along side existing wires and make it all look neat.

Swapping in a front wiring harness will get you the wiring from the front bulkhead to the accumulator / dryer. But you'll still be missing the wiring from the A/C control panel to the front bulkhead.

IMO, it would be a lot easier to run a couple wires from the A/C controls to the accumulator / dryer, instead of swapping out the entire chassis wiring harness.

If it's only a matter of running it into the AC control box I am not worried at all. What I AM worried about is where to connect the wires into the AC control box. I have an 86 GM service manual, but it is not organized well at all and has no index. I'm a little hesitant to look through 1,000 pages of technical info to look for an obscure diagram that may not even be in there...does anyone know what two terminals I need to connect the light blue and brown wires to that run out of the Receiver/Dryer?

Lastly, how do I make sure I'm even getting power to the compressor clutch? I have heard people make references to "jumping it out" but I am unsure of how to do this. When I rewired the compressor for the new 2 wire switches, I used a heavy duty spade connector in one spot so I could completely bypass the two switches and give power directly to the clutch, but even with this configuration, the clutch would not engage. I know my AC is charged, and charged with the right amount of freon, so if there was a way to give the AC clutch direct power and make sure it works that would be great. It is a brand new HR6 compressor, so I am not worried about it not working, I am only worried that because of wiring changes the clutch may not be getting the 12 volts it needs. It needs a ground on one terminal and power to the other with no regard for which wire is placed on which terminal, correct?

quote Originally posted by Blacktree: IMO, it would be a lot easier to run a couple wires from the A/C controls to the accumulator / dryer, instead of swapping out the entire chassis wiring harness.

New wiring to the AC control head isn't what's needed. What's needed is wiring from the accumulator in the front compartment to AC the compressor in the engine compartment. Probably the simplest arrangement would be to 1) jumper the wires that were originally connected old A/C Low Pressure Switch, and 2) connect the new Pressure Cycling Switch in series with the existing High Pressure Switch. Per the FSM, 18 AWG wire should be sufficient.

(From the 1986 FSM ... shading added)

[This message has been edited by Marvin McInnis (edited 06-15-2010).]

https://www.fiero.nl/forum/Forum4/HTML/052437.html

You guys should check this out. It is linked to this thread.

I'm not sure if the clutch is polarity-sensitive. But you could try flipping the connector around. You can also test the compressor clutch by taking two pieces of wire (around 18" long, or so), putting a female spade connector on one end of each wire, and plug those into the compressor clutch. Strip the insulation off the other end of the wires. You can then send power directly to the compressor clutch by touching the stripped ends of the wires to the battery terminals.

Also, the absence of the cycling switch will not prevent the A/C clutch from activating. It will actually do the opposite. The clutch will be activated continuously, until the high-pressure cutoff kicks in. So the absence of the cycling switch isn't causing your current problem. But it is something you will need to install. Speaking of which, the cycling switch splices into the light green wire coming out of the back of the A/C controls. It's pin "G" on the big flat connector. Snip that wire, and connect each end to one of the two wires coming from the cycling switch. it doesn't matter which wire goes where.

A couple more comments. If you get the wires crossed at the compressor switches, or get the wrong plug on the wrong switch, the compressor clutch will not work. The high-pressure cutoff switch has 2 pins. One connects to the ground wire (black) coming from the compressor clutch. And the other (also black) grounds to the engine block. If you have a multimeter, you can check for continuity between the black wire going to the compressor clutch and the engine block. The resistance should be zero, or close to zero. If the resistance is really high, or infinite, then there is a break in the wiring (or maybe it's plugged it into the fan switch instead of the cutoff switch).

Also, if there's any confusion as to which switch is which on the compressor, you can test them with a multimeter. With the engine off, the fan switch will have no continuity (i.e. infinite resistance). And the high-pressure cutoff will have continuity (i.e. almost zero resistance).

Hopefully this helped?

(edit for correction)

[This message has been edited by Blacktree (edited 06-15-2010).]

quote Originally posted by MadDanceSkillz: I know my AC is charged, and charged with the right amount of freon, so if there was a way to give the AC clutch direct power and make sure it works that would be great. It is a brand new HR6 compressor, so I am not worried about it not working,

Unless you have professional equipment, it is very difficult to charge the full "right amount" of refrigerant without the compressor operating. How much refrigerant did you charge, how did you do it, and how did you measure it? At this point I would be worried about damaging your new compressor 1) if there's not a sufficient refrigerant charge, or 2) if you don't have the right amount of the correct oil for the refrigerant you're using.

[This message has been edited by Marvin McInnis (edited 06-15-2010).]

Blacktree, that may be all the info I need. See the thread I linked to.

As far as the charge, it was done with a 4k Robinair machine at a professional AC shop. The car's AC had already been converted to R134a and the new compressor came pre-lubricated.

I hope you you get it sorted out. BTW, please check my previous post again before you start splicing wires. I had to make a correction.

It looks like, from the diagram above, that one wire from the cycle switch should go to pin G of the AC control head, and the other wire should go to pin A3 of the C100 connector.

Here is my recommended wiring, based on the '86 wiring diagram posted above being accurate:

1) Run two 18 AWG wires from the rear head of the AC compressor to the new "Pressure Cycling Switch" on the accumulator.

2) Connect one wire to each terminal of the "Pressure Cycling Switch."

3) Back at the compressor, connect an 18 AWG jumper between the "light green" and "gray/red" wires that were originally connected to the "A/C Low Pressure Switch." (The "Pressure Cycling Switch" is going to provide the low-pressure cutoff functionality from now on.)

4) Disconnect either "gray/red" wire at the "High Pressure Switch" connector. (No, it shouldn't matter which.)

5) Connect either wire from the "Pressure Cycling Switch" to the the "gray/red" wire you just disconnected.

6) Connect the other wire from the "Pressure Cycling Switch" to the now-free terminal on the "High Pressure Switch."

If your AC control head, "High Pressure Switch," AC relay, ECM, and AC compressor clutch are all OK, and if you haven't messed with anything else, you should be done.

(Note that doing it this way is very simple, and makes it easy to return the car to its original wiring configuration if you ever want/need to do that. If you can't tell, I hate having to troubleshoot hacked-up wiring jobs.)

[This message has been edited by Marvin McInnis (edited 06-16-2010).]

I just got my first cold blast of AC...here is what I did.

Ran two wires from cycling switch (Open between 20 and 43 psi IIRC) to the bright green wire at the control box and cut the switch into the wire. Back in the engine bay, I took my handy test light to the AC relay and discovered that when I tested the dark blue output from the ECM, it clicked the relay. So, just to test the clutch, I rearranged the spade connectors and bypassed the compressor mounted switches...bingo. The clutch popped into place. After splicing a ground into that blue wire to bypass the ECM/s say over the compressor being on, I have a power wire going into the compressor clutch that comes back out and goes through a low pressure safety switch (Normally open) and runs into a ground to the engine block. I know, it's not the best way to do this, but carbureted cars operate the same way. My compressor clicks on when I turn on the AC and right back off when I disconnect it.

But now, another two important questions.

I know the ECM turns off the compressor at WOT, or in other words, when you're enjoying your car. I am okay with sacrificing the 10HP or so while the AC is on, but when I wind the engine up to 4.5k and higher with the compressor on, will this hurt it? Like I said, carbureted cars with no ECM should operate exactly how my car's AC system now does, but I'm still concerned. Is running the compressor at a high RPM okay or should I be gentle now that it won't turn off at WOT?

Second...I now have no high pressure cut-out switch. Instead, I have a clutch cycling switch that is open to allow compressor cycling only between 20and 43 PSI or something like that on the low side. Is this sufficient to keep my compressor safe and act as a high pressure cut-out, or do I have to figure out a way to make the high pressure cut-out work?

By the way, thanks so much for all the help. It was a great feeling to get some cold air out of this thign today, and it sounds like I'm almost done with this mess...

The compressor cycling switch is normally open and closes when the pressure rises above it's calibrated setting. This would normally be around 35 to 45 psi. It will open again when the pressure falls below approximately 20psi (for 134a). It does not open for high pressure. There should be a high pressure relief valve to protect the compressor and components mounted on the back of the compressor. If that valve "blows" off you will know it. If all the other components and hoses manage to withstand the high pressure, you will not have damaged anything but you will have lost some freon and oil. The high pressure valve should close (reset) by itself and you should be ok. However, these cars are old and you may have a hose or some other component burst before the high pressure relief valve opens so you run that risk.

Charlie

quote Originally posted by MadDanceSkillz: Is running the compressor at a high RPM okay or should I be gentle now that it won't turn off at WOT?

High rpm operation may (or may not) be OK, since the Pressure Cycling Switch will still disengage the compressor clutch based on low-side pressure. That said, you have disabled all of the protective features designed into the system by GM. You have to assume that the GM engineers knew what they were doing and had a reason when they included them in the original design.

quote I now have no high pressure cut-out switch ... do I have to figure out a way to make the high pressure cut-out work?

Yes. Not only does the EPA require it (if anyone cares), but its other purpose is to prevent damage to the system if the Pressure Cycling Switch fails, or the condenser becomes obstructed, or the radiator fan doesn't work as intended. "Do it right or do it over."

Why are you so intent on making the problem more complex than it needs to be? The wiring I described earlier preserves all of the safety features GM designed into the AC system. All you need to do is wire the "High Pressure Cutoff Switch" in series with the "Pressure Cycling Switch" and ensure that the radiator cooling fan runs whenever AC is selected.

[This message has been edited by Marvin McInnis (edited 06-17-2010).]

I think you said that you by-passed the high pressure switch? If you did take the two wires from that switch and run the compressor power wire to one, then the other to the compressor clutch. This is a normaly closed switch. High pressure would open it up and dis engauge the compressor , The last one from the clutch would be grounded. You now have a high pressure switch in the loop.

Marvin McInnis is telling you correctly

[This message has been edited by josef644 (edited 06-17-2010).]

Will this work on the high pressure line fitting up front;

https://www.ackits.com/pc/57807MD/conversionitems/Low+-+High+pressure+Cut-off+Switch


I forgot who posted it but I purchased one along with a dryer from those guys.

[This message has been edited by Joseph Upson (edited 06-17-2010).]

quote Originally posted by MadDanceSkillz: Second...I now have no high pressure cut-out switch. Instead, I have a clutch cycling switch that is open to allow compressor cycling only between 20and 43 PSI or something like that on the low side. Is this sufficient to keep my compressor safe and act as a high pressure cut-out, or do I have to figure out a way to make the high pressure cut-out work?

A standard Harison HR6 compressor, as used in V6 Fieros, has two switches on the back of the compressor. One is the high pressure cut-off switch, and the other is a fan back-up switch, which is supposed to make sure the radiator fan is on if the pressure gets too high.
A hew compressor will have plugs in the switch holes. You are supposed to transfer the switches from your old compressor, or buy new ones.
On the V5 compressor, as used in some 4-cylinder Fieros, the two switches in back are different. One is a high pressure cut-off switch, and the other is a low pressure cut-off switch. The compressor is supposed to run all the time with neither switch activating.

TopNotch I'm not trying to get an argument going here, but the low side switch is open on a V5 until a value in the neighborhood of 25lbs pressure is present. That closes the switch so you can add more refrigerant to the system and the clutch will engage. This is so the compressor doesn't self destruct while running without refrigerant and its system oil we put in the accumulators and compressors.

High side is closed until to high pressure opens it interrupting current flow to wherever.

I converted a no AC ,86 coupe with the 2.5, to a factory AC car. I learned a lot in the process of doing this conversion.

From the FSM page 1B-2

"Because the pressure cycling switch is not used with the V5 compressor, a low pressure cut out switch is used to protect the compressor from a low pressure charge condition". And so one etc.

Joe

[This message has been edited by josef644 (edited 06-18-2010).]

quote Originally posted by TopNotch: On the V5 compressor, as used in some 4-cylinder Fieros, the two switches in back are different. One is a high pressure cut-off switch, and the other is a low pressure cut-off switch.

quote Originally posted by josef644: TopNotch I'm not trying to get an argument going here, but the low side switch is open on a V5 until a value in the neighborhood of 25lbs pressure is present.

You are both saying the same thing, and you are both right.

Marvin you are correct. I forgot to look at it from the other side. TN apologies are in order here, and I offer them to you.

Joe