XxMerlinxX

iTrader: (2)

Just had my A/C recharged with R12. Now that that's been done, the car stalls whenever the compressor tries to come online. I've tried messing with the idle in case the ecu thought the car was stalling and turned the A/C off, but no luck. Even by giving it a little bit of throttle, the a/c compressor still cuts on and then immediately back off while reving it. Any ideas?

XxMerlinxX

iTrader: (2)

Ok, how 'bout this, does anybody know what the pressure readings should be on the two different A/C lines? I'm starting to think the system might have been either under or overcharged.

Speed of light

iTrader: (8)

When running, with the compressor and fans on, typically it should be around 30-->50# on the low side and 200-->230# on the high side. If the ambient temp is high or the condensor is blocked then the high side could be more, but if it's really high, say >>260#, then something is wrong.

The EL unit attached to the ecu should help compensate for the additional load by raising the idle when the a/c is activated.

So why did you decide to go with R12?

If it was properly vacuumed and charged by weight (about 2 pounds), it should be okay.

XxMerlinxX

iTrader: (2)

The shop had some on hand and he only charged me $50 for it. But we've decided it can't be an overcharge/undercharge issue as 1.) It was doing this before the recharge and 2.) the sight glass is clear.

That leaves me with a possibly bad relay or compressor, neither of which offer me much hope.

gracer7-rx7

iTrader: (16)

Sounds like an issue with the Idle Speed Control solenoid. Search for ISC and look at the FSM to review how to test it.

Speed of light

iTrader: (8)

The ecu + EL unit controls the idle speed and mixture. Chances are that it's not the a/c causing the problem, but rather, related to the ecu control/compensation. Time to get out the shop manual and check their procedure for diagnosing this problem.

The problem is not your a/c compressor, so you can forget that. Additionally, the primary refrigerant control is an expansion valve, so these systems shouldn't be cycling the compressor that much, esp. at idle. If you still think there is an a/c problem, put the gauges on it--otherwise you are just speculating and wasting your time.

P.S.: The sight glass can be clear under certain overcharged conditions. It should not be used as an indicator for charging the system unless you really know what you are doing. The best way to charge a system is by weighing in the refrigerant.

XxMerlinxX

iTrader: (2)

Made some progress. I unplugged the refrigerant pressure switch and jumped the connectors together. Wa-lah! Cold air! But I'm not sure what this means? What does the refrigerant pressure switch connect to that's making it go bad?

bajaman

Overcharge will make the compressor pull harder. Undercharged and the compressor won't come on without bypassing the switch.

purerx7

iTrader: (61)

good luck ive had this problem for over 2 years and replaced both the tps and isc with no luck.

Speed of light

iTrader: (8)

Don't assume anything is bad until you put gauges on this and see what the operating pressures are. The high/low pressure switches usually don't go bad--they are there to protect the system and their operation is symptomatic. If there is an obstruction in the high side, a severe overcharge, or a bunch of air in the system, then it is possible that the compressor is being cycled by the high pressure cut out. This will load the compressor much more than normal, so don't operate it this way until you locate the problem. (It also follows that an undercharge can cycle the compressor with the low pressure switch.)

If the high side pressure is LOW and the low side is HIGH at the service ports, then you may very well have an obstruciton on the high side (or the smaller liquid lines) causing a problem.

Cycle times for this a/c should be long, >30 seconds or longer. If it is "short" cycling every few seconds, then you definitely have some sort of problem. Check the freakin' pressures!!!

XxMerlinxX

iTrader: (2)

Pressure on the high side, sitting outside in the sun in 98* weather while being revved were around 380psi. Just sitting at idle it was around 100 psi lower. I don't know what this means, other than 380 makes me extremely nervous. Also, our fans are two speed, but it never seemed to cycle to high at any time. I'm assuming I can drive around with the connector jumped as long as I don't run the a/c on all the time so as to avoid it freezing over. This is obviously not a good fix, but I'm at a loss as to what to do. On the wiring diagram in the body electrical manual, the pressure switch looks like it connects to the thermoswitch. If this is the case, and the thermoswitch is bad, I'll have to lose the R12 I just got (which was his last btw) plus replace the thermoswitch and I'm not even sure how to do that.

Any thoughts?

Speed of light

iTrader: (8)

380 PSI?

Houston, we have a problem....

380 psi is almost twice what it should be and 280 at idle is still 100# high. DO NOT OPERATE the system in this condition. Something is seriously wrong. What is the static pressure just sitting there after everything has been off for a while and cooled down? Is the pressure equalized--the same on both sides? How was this system charged? What you describe sounds like a serious overcharge... but it could be a combination of problems. Are they sure that its R12 and not some other high pressure refrigerant (like R22)?

Can your guy recover the refrigerant? You can go buy a small size, empty propane cylinder at wal-mart for $16 and, with an adaptor, use it to recover the R12 (this is how it's done).

First thing to do--read the vapor pressure of the refrigerant under static conditions.

veilsidei

my car stalls too when it does this and i recently had it charged before that it worked fine. but i try not to use the A/c i might live in vegas but i get bad enough gas milage i dont need it to be worse.

Speed of light

iTrader: (8)

So what's the verdict on the 380psi?

After considerable thought, there are really only 3 ways to achieve this:

1) Severe overcharge of refrigerant (and possibly oil too--though it would take a shitload);

2) substantial amounts of air in the system (due to improper evacuation);

3) wrong or contaminated refrigerant; or,

4) all or some combination of the above.

There really isn't much else it could be--you didn't say what the low side was, but at the quoted temperature, even a completely clogged metering device (txv) would not cause these kind of pressures at the service port.

You guys that don't think you have to pull a vac (on a system that has been apart or open), or are going to try to "burp" the air out, pay close attention....

Good luck

Busted7

Could be a clogged filter dryer its on the high side and before expansion valve! It would cause high head and low suction.

XxMerlinxX

iTrader: (2)

When I typed all this out I had been up for two days and I got some stuff mixed up. It wasn't a total evacuation and recharge, it was only 1 can added to what I already had. The viewing glass on the drier was cloudy and when we added the one can it cleared up, so that's how we know that it was low. When he put the gauges on it, he said it was a bit high but not enough to be worried about. If I remember correctly now, while running it was 340 and not 380 and did sit dead on 250 while idling.

Granted this is still high, but for the moment I don't think there's really anything I can do about it. I'm almost positive that the problem with the compressor is that my thermoswitch is bad. There's really no other reason for it to kick on and off like that. As to what I'm going to do about it, I'm still not sure.

Speed of light

iTrader: (8)

Your system's pressures are more than a little high for an R12 system--they are beyond normal design limits for the conditions posted which is the reason it's cycling the High pressure limit switch; that is what it is supposed to do since it's there to protect the compressor.

High pressures result in mechanical stresses and very high discharge temps which are harmful to the oil and the compressor. FWIW, High pressures & temps are the leading cause of R134 system compressor failures--something relatively unheard of in R12 systems (unless you run it out of oil). The pressures you quote are in excess of even a 134 system's pressures on a hot day.

So maybe you are not overcharged, but you still have a problem with either air in the system or contaminated/wrong/mixed refrigerant. Sadly, the solution will be to properly evacuate the system and refill it. Anything else is just wishful thinking.

It could cause these symptoms, but not in this particular case because the HS service port (where the pressure is measured) is downstream of the receiver/dryer, near the evaporator. Clogged condensors have been known to cause high discharge pressures, but generally, small a/c systems are designed so that the condensor and receiver will hold all of the refrigerant without excessive pressure.

Busted7

I did not consider that. Im used to houses and commercial units. I agree he should remove and evacuate then weigh in the charge as to know that he is not over charged. 22 would go crazy in the invirement of a car hope they didnt get mixed up!