On Sunday, I replaced the alternator belt (which in my 86 2.5l/5speed Fiero, requires removal of the A/C belt first). I also checked A/C gas pressure with a stick guage and it seemed good (green range).

I went for a short trip that same day . Everything seemed well, including the A/C. It did take a little more time than usual to cool things up. Yesterday, however, no cool air was blowing (blower works). The compressor clutch seems to engage, but may not be staying engaged - hard to tell. It appears that there has been no gas leak, so the low-pressure switch is not a block. The coolant fan runs with the A/C on.

- I initially suspected the comp. clutch relay but found that someone had cut 2 wires in the past. I still have to find out what they re-routed.

- The high-pressure switch is also a suspect, but how do I test without tools?

Would a clog cause this -- likely where? I can't find an inline filter/orifice thing.

BTW, this a V5 compressor.

TIA
Benno

The orifice is in the aluminum pipe just behind and to the left of the T piece adapter that is circled in the pic (part of my ac conversion pics). This is under the heater blower fan up front.
At least with the V5 compressor you do nto have the pressure switch on the accumulator to worry about. Sounds like you just disturbed something if it was working ok before, could be bad connector to the compressor or around that area. I guess a circuit tester (or bulb and wire ) might help you find any problems.

------------------
Dave E

www.ltlfrari.com

[This message has been edited by ltlfrari (edited 09-30-2003).]

Check your pressure again,sometimes the schrader valve fails to seal again after you disturbed it while checking the pressure,this happens rather often if the protective caps have been left off in the past and a little dirt gets in there and ends up in the valve when you depress the valve. put a little soapy water on the valve opening see if it makes bubbles,if so you have found your leak. my.02$

[This message has been edited by mvstar (edited 09-30-2003).]

Thanks for the picture, Ltlfrari. I was having a hard time locating it in a parts list file.

Mvstar, yours was my first thought, as well, even though the cap was on. For now, the system seems to have a good charge but I may have to get a more accurate guage to be sure. The compressor clutch engages for the briefest time. Then it is hard to tell if it is on, and if I turn A/C off or switch to Fan mode, tach revs don't change much -- nor is there a clutch click. This could probably happen with low system pressure just above the level needed to prevent low pressure switch contact. (Yet, the guage says there's plenty of gas.) It must be off, I think.

BTW, are the high and low pressure switches the same pressure switch unit on the back of the V5 compressor? The diagrams show them as 2 distinct units (high and low) but no such names appear in the parts list.

So far this is the order of my suspects, please be my sounding board:
1- Bad pressure switch contacts. Why? The A/C clutch relay was bypassed. I found what appears to be a straight path from the clutch to the pressure switch. I am judging this from diagram wire colors vs splices seen in the harness. The thinking is that without the relay (a kind of buffer if, you will), the contacts in the switch could be getting fried more quickly. If this turned out to be the case, would I have to discharge the system to replace it? ...probably
OR
2- Good pressure switch responding to some blockage from debris probably caught in the orifice tube. It is an old compressor. Something must have shed particles by now...

A happy outcome would be for me to discover that I did in fact disturb something electrical that just needs to be plugged back...but what? And why work fine for a couple of hours but not the next day.

Benno

get someone to do the switching while you watch the clutch,if it engages breifly then disengages try taking the connector off the low pressure switch and connect a kumper wire across the two connectors in the plug and see if that engages the clutch, if so you are either low on freon or have a bad lo pressure switch(least likely)the low pressure switch can be replaced without loosing freon as the port that it screws onto has a schrader valve in it,DO NOT leave the jumper wire on for more than a few minutes as the compressor will be damaged if the freon is that low.The reason for the switch.oops just read the post that says you dont have that switch on your system,mine does Sorry

[This message has been edited by mvstar (edited 10-01-2003).]

Thanks, that's ok. Anyway, I scratched out my own 2 suspects. To make a long story short, the clutch is working. Ergo, the pressure switches are ok, for now. Even my suspicion that the high pressure switch was being activated by blockage didn't turn out to be true. The clutch stays engaged as long as the A/C is on.

And while the air is not being cooled, there is a little portion of metal tubing that is cold enough to sweat. It is the portion that goes to the evaporator inlet after a fitting, just below the accumulator.

Given Ltlfrari's picture, I now suspect that if I open that fitting I'll find the orifice there and it will be, indeed, clogged. If so, I would have expected a clog to provide enough back pressure for the H.P. switch to activate and shut off the clutch. It doesn't happen.

So, I am not 100% sure of anything...but now I am willing to bet that replacing the orifice tube will deliver results -- even if the compressor is going south anyway. I would have to get proper guages, evacuate the system and get a vacuum pump before recharging. As always, these things happen when the dollar tank is empty!

Ideas continue to be welcome and very much appreciated.

Benno

[This message has been edited by Jdlog (edited 10-02-2003).]

you can make a good vacuum pump from the compressor of an old household fridge all you have to do is solder a 1/4in male flare fitting on the suction tube where it comes out of the sealed compressor,i have had one for several years now, it pulls a good vacuum and has done far more jobs than i ever thought it would as i just made it up to carry on my boat for emergency use and never intended to use it on cars but it works great.

From Ogre's Cave:

quote AC/Heat Mode Actuators The Fiero is somewhat unique in it's use of a Servo Motor system to operate the dampers in the AC/Heating unit in the passenger compartment instead of more traditional vacuum motors. These electric devices are controlled by a set of push buttons mounted above the radio.

Are you sure the vent dampers are operating correctly? If the orifice tube is cold, it's working to some degree. If the servo motor is not operating you may be getting air from outside or through the heater core and not the A/C evaporator.

Well, as it turned out the stick guage was off by quite a bit. I bought a guage that I can use on both, Hi/low sides and things changed. Simply low on gas. Recharged with some 134a gas/UV marker and things are cool for now. I'll just have to get a blacklight to find the leak.

However, the compressor is now making a "tapping" noise, similar but lower pitched than engine valve sound. I am fearing that the days of this compressor may be numbered. OTH, the A/C comp. on my Silhouette minivan made the same kind of noise for a while. The I added ester oil and it went away 40k miiles ago.

I did add 2oz of ester to the Fiero today, but I don't know if it is wise to add more. Would a loss of refrigerant of about 18-20oz be enough to drain a lot of oil? (I am estimating this loss from the amount it took to recharge.)