VehiGAZ

Hi all,

I bought my 1989 GT a month ago and I haven't gotten my manuals yet, so please cut me some slack on my ignorance and inability to figure this problem out on my own, but I need to get this fixed - it is too freaking hot to be driving around without A/C while my Isuzu is in the shop getting S/C'd this week! I searched the forums today and found vacuum and electrical problem diagnostic procedures, but have not executed these yet. I found several other A/C system problem threads, but the descriptions did not match my symptoms. I also found lots of references to the heater valve not closing due to vacuum leaks, and while I have reason to suspect that I have some other vacuum leaks, I do not think this is the problem based on the symptoms described below.

The A/C was working perfectly during a long drive on June 30 (cycling on-and-off to maintain interior temp setting of 72*), then it was not working at all the next time I drove it on July 4. I was driving home that night in the rain after a 4th-of-July BBQ, the windshield started to fog, so I pushed the A/C button with the climate control temp set on coldest setting (65*), but there was no change in temp (and no clearing of the windshield). I tried different ventilation patterns with no luck, so went to full-frontal-defrost mode to clear the windshield. It was blowing all hot air with no cool air in the mix at all, which is why I don't think it's the heater-valve problem mentioned above. The hot defrost cleared the fog, but WOW - full heat on a hot, rainy, sticky night is a disgusting feeling.

But I digress... I checked the fuse, and it was OK. I have not checked the relay operation with a multimeter, but I will tonight with the diagnostic procedure I found. When I press the A/C button, the button light turns on, the cooling flaps in front of the engine open, and the fans kick in, too. I checked the condenser sight glass with the A/C engaged but saw no activity (no streaming, no bubbles, but it did not look completely empty to me either, FWTW), but I could not check for charge with a gage for lack of same. BTW, it was converted over to R134a by the PO.

Here's where you can snicker... I confess that I don't know for sure which engine component is the A/C compressor, but the "belted accessory component" on the lower left (while looking at the engine) seems to be the most likely candidate, because it appears to have an inner hub inside the pulley which is driven by the belt. If this is correct, this inner hub (A/C clutch) did not engage and rotate when the A/C button was pressed. If I'm looking at the back side of my Fetzer valve instead , please tell me where the compressor is and how to determine if the clutch is engaging, and I will check that too.

With these symptoms, I do not know where to start looking for the problem, so I'm looking for learned suggestions. My best guesses are that either my compressor is not engaging when it should or I lost all of my refrigerant in a couple of days and the compressor is not engaging due to low charge. The former seems far more likely, of course, but I've also quickly learned that these machines are far, far more complicated than I should assume, so I know anything can go.

Thanks guys!!

Imo000

GAZ,

The 928 is not really all that complicated. You just need to get to familiarize yourself with it a little. I would suggest to take the car it to a good SC shop and have them diagnose the problem. From there you can decided if you want to tackle the job yourself or have the shop do it for you.
There are so many things that could go wrong in an AC system that remote diagnosis is very difficult.

RngTrtl

You live in CT, is air conditioning really that nessasary? Don't y'all only have like 3 days of summer?
Just kidding, welcome and I hope that you get it figured out.

Alan

You are looking at the right thing. The easiest test is to locate the pressure switch on top of the dryer - take off the connector and test the switch...

It should be closed circuit to run - if its open circuit it means the pressure is too low or too high. Since the system hasn't been running it would pretty much have to mean too low in your case - meaning a freon leak.

The dryer is in front ofthe radiator on the pass side..

Alan

ROG100

Hi Gaz,
Welcome - I have a copy of the HVAC document written by Wally - the expert.
This will help you understand and troubleshoot the system.
PM me your email address and I will send it to you.
Roger

VehiGAZ

Thanks Roger! PM sent.

Imo - Dan Jacobs is going to check a few of my concerns out and give it a full physical, but not for another 2 weeks. The A/C can't wait that long.

RngTrtl, we here in CT are in the middle of our allotted 3-day stretch of summer right now. I went out to get lunch and the outside temp gage said 108* which was just nonsense - it couldn't have been more than 96*. Still, with this humidity...

Alan - thanks for the confirmation. I will test the switch on the dryer and will probably get an A/C pressure gage set tonight while I'm at it to see if there is freon in there or not.

Assuming I have adequate freon, how would I test the compressor to see if it is working (but not getting the "on" signal) or not?

Big Dave

My A/C went from 100% functioning to 100% not functioning when the compressor (I assume) blew a seal and lost all the freon. I actually heard it escaping when I shut the car off.

I suspect you've lost pressure. An A/C shop should be able to test for pressure easily and cheaply. You can start hunting down other possible reasons once you've ruled out a leak.

Imo000

There is no need to wait that long. Just take it to a good local AC shop and have them test the AC system. These shops specialize in AC so they can give you a really good diagnosys. Then you can decided what to do.

In the mean time, is there any pressure in the system? There should be quiet a bit. Should feel aobut the same feeling as when you let soem air out of a tire. If it's none or very little the R12 have leaked out somewhere.

VehiGAZ

I can definitely take it to Valvoline today to see if there's any refrigerant in the system, but I like your method better. Where exactly is the low-side fill port? And where is the anti-freeze switch? Roger sent me the diagnostic procedure, and that's one of the things to check. But without service & tech manuals, I don't know where to look or what to look for.

VehiGAZ

OK - I found the anti-freeze switch and determined it's not working correctly. By Wally's excellent diagnostic procedure that Roger provided, I found that it has 12V only on one connector, and nothing on the other. When I bridged them, the compressor kicked on and engaged the A/C. There were bubbles in the dryer sight glass, so I probably need a charge-up, but it's not low enough to shut off the compressor.

Does anyone know if it is OK to run the system short-term with the anti-freeze switch bypassed (with the two wires connected to each other)? I would take care not to run in recirc and with all vents open.

Thanks!!

docmirror

i'm a bit late but I would say if you bridge the switch very long you'll pump all your R134 out and the lube too. not good. you need to find and fix the leak before damage is done.

VehiGAZ

Doc, there is no leak. The problem is that the anti-freeze switch is refusing to let the compressor run. Since the system hasn't run in a week, and it's been Teyxas-hot here since, I am sure the evaporator is not frozen. :-)

dr bob

Gaz--

OK to run for a while with the anti-freeze switch bridged. There's a risk thatthe evaporator will ice up, especially in humid weather. You'll notice a reduction in airflow through the vents at first, then it will get warmer and the air will really slow down as the evaporator turns into a block of ice. So as soon as you notice a reduction in airflow, or say every 20 mins of driving, shut off the AC for a bit and let the evaporator thaw and drain off. The condensate from the evaporator is supposed to drain out through the floorboards near the tunne; if that drain is plugged, the condensate will end up draining through the electrics panel at the bottom of the passenger footwell. Not a good thing! So watch where it drains, and don't run it so long that the drain freezes.

The new switch isn't hard to install. Be careful with that little copper capillary tube that pokes into the evaporator housing. It's fragile of course, and any kinks or breaks in that tube make the switch junk instantly.


Welcome to the group, by the way. You've discovered what is arguably the best owners' resource for keeping your new toy alive and happy.

ROG100

It should be OK to run the system with the freeze switch jumpered.
The freeze switch is there to stop the evaporator freezing up.
Short journeys should be OK - no long stints.
I will email you about a freeze switch.

VehiGAZ

I love you guys! And thanks for the welcomes! I know the value of forums - my daily driver is one of the ultimate orphan cars - the Isuzu VehiCROSS. But the knowledge base here at Rennlist runs a hundred times deeper.

I will manually cycle the A/C while I drive.

By the way, to what does the other end of that switch capillary tube connect?