Hello Everyone and thank you all for making Pennock's Forum such a great place to learn about our cars,

I've been reading up on fieros for years, and have loved them since they were new, last week I finally took the plunge and picked up my first. I am now the proud, but sweaty owner of a 1988 5spd Formula Fiero (2.8l getrag, notchback).
Being an MD resident, I am scrambling to fix up a few things and have about 20 days left to make my ride pass MD's stingent safety inspection. I'm making progress on getting everything operating correctly, but the A/C system has me stumped.

Problem #1: My blower fan- Vent/Heat/A/C only works on the lower settings, When I turn it to max it turns off. I researched the problem and believed it to be my High/Low Blower Relay #4 in the photo

I found one for $15 at advance auto and swapped it in. As I drove home I turned the blower to max and it worked! I had a huge grin on my face and was so proud of myself, but then the next time I started her up and turned to max vent, it died again. So I think something is frying my relay Does anyone have any idea what can cause this or where I should start looking?

Problem #2: The previous owner told me the A/C didnt work when he got the car and he never really cared because he just drove it with the ttops off most of the time. A/C The A/C does not get cold, when I turn it on the Compressor clutch engages for a second then disengages. over and over again. I'm no A/C expert or any expert, but i'm not afraid to tinker or I wouldn't have purchased a 24 Y/O car. I put a pressure gauge on the low side service port (and yes the R12 has been replaced by someone with R134a since my gauge has R134a fittings and would not have fit on an R12 fitting or so I've read. ) The pressure seemed normal ~ 40-50 PSI and no sign of leaks. I suspected that maybe the low pressure cutoff switch was faulty and telling the compressor to stay off? I attemped to test that theory by removing the sensor from the accumulator and shorting the contacts with a piece of wire. This method led to the compressor staying on, but unfortunately after running for a few minutes I saw no drop in air vent temp, so I shut it down to avoid causing any unnessacary damage. My current thought is that I may have a blockage in the orifice tube and its preventing all the cooling goodness from getting through? Does that sound likely? any suggestions? I am planning on taking it to a shop since I have no tools for refrigerant recovery or the know how to run a vacuum on the system to recharge it. I bought a new orifice tube, accumulator and o ring set that I will ask the shop to put on when they drain the system.

Thanks for any advice you can offer,

John

Hello, and welcome to the forum!

Problem #1: The high-speed circuit is simple, and since the blower works on the lower speeds, rules out quite a bit. The first thing to check is if the high speed blower relay really is fried or not. Check for continuity between A and C on the relay (where the orange and black wires go in). If there is, unplug the relay, and hook up a 9V battery between terminals A and C, you should hear a click sound. Now check for continuity between D and B (where the red and purple wires plugged in) and measure the resistance, it should be very low. If this works, the relay is OK, and that pretty much just leaves a wiring problem. Turn the blower on high on the dash, and see if there is 12V at the orange wire, try wiggling the wire harness around to see if it breaks continuity. Similarly, the black wire goes to ground.

Problem #2: The compressor quickly cycling on and off usually means the system is low on refrigerant. Since the pressure on the low side is kinda high unless it was really hot out when you took the pressure reading, it sounds like the gauge isn't very accurate? It would help to have the high side pressure, too. There probably isn't a blockage on the low side since the pressures are so high, and there isn't any icing on the low side? Really need to see high and low side pressures to make a decent guess. Careful the shop doesn't try to charge you $1000+ to work on the AC system.

Thanks for the advice, I will be checking the relay and try your methods tomorrow I have a few work things to take care of tonight so enough playing with the car. I just got back inside after adding a $5.99 Grounding strap thanks to an excellent write up here in the forum. I'm hoping it helps steady out my RPMs and I even heard someone say it smoothed out his shifting? I guess I'll find out on my drive into work in the morning. You mention the Pressure was High, but keep in mind that reading was at a humid 95 degrees outside and appeared to be within the normal range on the gauge. In MD repair shops have to tell you up front the cost before they do the work, so if I hear $1000 I'll be moving along to someone more honest. Even if its the compressor I've seen them for $160 with the mag clutch (rebuilt)

Problem #1: It is possible that the new relay you bought is defective. It's also possible that the fusible link supplying the relay has opened or there is some other wiring fault. As RWDPLZ observed, the blower high-speed circuit is pretty simple. You should be able to find out all you need to know by probing with a voltmeter at the relay socket.

Problem #2: Your AC system is low on refrigerant, but not completely empty. The fast compressor cycling is the classic symptom of low refrigerant charge, but you cannot determine state of charge by pressure alone. The saturation pressure of R-134a is 71 psig at a temperature of 70 degrees F ... from system almost empty to system almost full. Since the system is still under pressure, evacuating it will not be required. While unscientific, adding two 12-ounce cans of R-134a to the system will probably restore proper system operation ... at least until next season. Between now and then you might want to find out where your system is leaking refrigerant. A system that's never used will often develop a slow leak at the compressor shaft seal, and sometimes just using the system occasionally is all that's required to "fix" the leak.

Thanks I'll be adding a can of refrigerant tonight with leak dye in it and I'll whip out my blacklight to see if I can find a leak. I was afraid to try adding anything since the pressure seemed alright. Looks like I'll be busy tonight. I'll get back on the forum and let you know how it goes.

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1997 Grand Prix GTP-(totaled)
1993 Firebird Formula-(Sold)
2006 Grand Prix GT-(Sold)
1988 Fiero Formula 5spd T-tops - Current Ride

Its better to burn out then fade away (but you go through more tires)

Just be careful to purge the service hose(s) before charging to prevent introducing any air into the system.

Sorry for my ignorance, how exactly do I purge the said hoses? Are you talking about the hose from the can of refrigerant to the fitting on the acumulator? I believe the hose stays charged, since the fitting self closes and seems to be under pressure.

What do you have in the way of a charging hose? From the pressure you reported in your original post I assumed that you at least had an R-134a manifold gauge set.

If you only have a single hose, you can attach it to the low (suction) side service port, loosen the hose fitting at the other end, and open the service port valve slightly for a couple of seconds to purge air from the hose, close the service valve and re-tighten the fitting, and then charge the system normally. A professional charging station would prevent any release of refrigerant to the air, but a de minimis release like this isn't illegal.

Had a chance to try things out tonight and here are my findings:

A/C I added a 12oz can of UV leak detector R134a and my A/C is blowing cold
I'll monitor it for now and if it stops working again I'll know it leaked and I'll turn on the black light to find out where.

The relay however is still trouble.

I'm not sure if my letters are the same as yours, but as I describe them here are my results, A to C on the relay has continuity, but with 55 ohms of resistance on the old GM relay and 86 ohms on the replacement I bought. B to D has no continuity at all on either relay. I tired RWDPLZ's suggestion with the 9V battery and A to C does make a click when it contacts the 9V, but there is zero continuity between B and D before or after clicking the relay with the battery. I don't know what to make of this, but Since they are both behaving the same, I assume I either have 2 good relays or 2 bad relays now. I'm still learning, but I assume that A and C are power + and - and that B and D act as a gate that opens and closes when A and C get a power signal? If B and D are no longer working than the gate is stuck open, perhaps something is causing it to get too much current and its breaking the "gate"

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1997 Grand Prix GTP-(totaled)
1993 Firebird Formula-(Sold)
2006 Grand Prix GT-(Sold)
1988 Fiero Formula 5spd T-tops - Current Ride

Its better to burn out then fade away (but you go through more tires)

[This message has been edited by FearArrow (edited 08-20-2012).]

So far so good! A and C are the relay coil, and should have continuity and resistance. Now, use a 9V battery to apply voltage to terminals A and C, and check for continuity and resistance between B and D. There should be continuity and VERY little resistance.

ahh after I saw your picture I realized you meant to keep the 9V on A and C while testing B and D ? I tried it again that way and I heard the beep of the multimeter indicating continuity, so I suppose I have 2 good relays. I was just a dummy and tested them wrong, doh! I wish I could understand your color coding of the socket wires, unfortunately my fiero has a red wire on B and 3 brown wires on the others...

Its getting too late to keep this up tonight, but I'll be checking the 12v on the socket in the car tomorrow.

thanks for your help, and great picture explaining this process. Maybe i'm just a visual learner, but when people put pictures like these up, it really helps people learn the concepts and find the right parts in the car.

Well that's good news! About the brown wires: The A/C Power Relay right next to the High Speed Blower Relay has red, brown, pink, and black wires. I also noticed in the service manual, the page you posted identifies the relay closer to the passenger side of the car as the High Speed Blower Relay. On the very next page, the positions are reversed! On my car, the High Speed Blower Relay is the relay closer to the driver's side, and the wiring colors were consistent with the diagrams, which is how I knew I got the right one. In other words, you might be checking the wrong one, check the wiring colors at both.

hmm very good point, I looked back at the service manual and sure enough the next diagram shows them reversed ? I thought maybe one is the 4cyl layout and one is the V6 layout since they have different compressors, but I could not find any mention of that. When I get back to the garage tonight I'll try pulling the other relay and check those wire colors. Having A/C on the drive into work this morning was magical thank you guys for the tips.

Problem solved, It was the other relay I popped it in and all fan speeds work just fine. I now have a fully functioning A/C system. That'll teach me not to read the service manual. Of course now that my a/c works summer is winding down and its been about 60 f outside on my drive to work. Oh well.

Case closed I guess, hopefully this write up and the diagrams can help someone else down the road.