yet another A/C problem

[johnsealey]

Hi All,

i have been searching and reading with intrest all the threads about AC and that has been a great help. but i would still apreaciate a little advice my a/c was very weak so filled it with 134 last week and it seemed ok not great but ok.
i took the car for a drive of about and hour and the air stopped working. it started to shudder and stall at low revs then started to overheat. have since drained and cleaned the radiator and renewed coolant etc.

today i checked the ac system and its empty but have done a check and dosnt seem to have a leak. is it possible that the pressure swich would cause it to chuck out the gas over a week or so...?

i have just left the Ac system charged with air to see if it leaks out over the next couple of days. just to make sure its not a slow leak.

i noticed that as soon as i put on the ignition the fan comes on, and i have only ever noticed one speed so there is suspect number 2.

As i am in Nicaragua so parts and expertise are non existent so i am slowly working through the usual suspects mentioned in the threads. could the relays be bad and therefore have the fan direct.or even the previous owners.

Oh and the revs dont rise when i put the Ac on why would that be? it seems that the compresor is turning but not adjusting the revs which obviously could be why the car misbehaves at low revs i guess.

i am without a place to buy relays, pressure switches, fans etc so please if anyone can help me locate the problem first then i will tackle the problem of the parts needed to fix it.

Thanks John

[CREWZIN]

John,

You might have a PCM (computer) problem. The PCM has the control over which speed to turn your fan on (with help from sensors) and it controls the raising of the engine speed when the A/C is enguaged to help compensate for the loss of power from the A/C.

The high pressure switch will blow out excess R134 when things start to overheat, like when you high speed fan isn't working. If your sure you have no leak anywhere, that's about the only place it can go.

Excess heat will also make the engine stumble and shake at idle.

First thing to do is find out if the high speed fan is working.You can tell the difference because the high speed is very loud when activated.

[johnsealey]

Thanks crewzin.

i left 220 lbs of air in the system and it lost pressure over a day and a half it took me all day but i found a small leak at the pressure switch on top of the acumulator as it has a plastic nut and the o ring had been damaged so replaced that and put some pdf tape so lets see if it hold the air again filled it with another 200lbs of air as its a lot cheaper.. ha ha

so i will try and recharge it with r134 tomorrow if all is well, but i am concerned why the engine isnt raising the revs on starting the A/C. and the fan is on as soon a i put on the ignition it seems loud but i have never heard another with which to compare it.

Is it only the pcm that controls the revs or is there a sender or vacum on the compressor that could be to blame? There are no codes showing so i imagined the pcm is ok, would the relays make the fan direct, or only come on either high or low only?

At least i found a leak so im one step nearer to solving the problem, any more advice always more than welcome

cheers John

[CREWZIN]

This is from PT Do-It-Yourself.net:

The hot air is from the engine heating up the plastic ductwork and the air intake drawing from the engine bay. It cools after the evaporator coils have begun to circulate the Freon in the AC system. This can take a minute. Try turning the air on the lowest fan speed for a half minute prior to setting it at full blast. The engine rpm should increase to compensate for the additional engine load from the AC compressor. If it's not, there may be a fault in the idle speed control system. The AC sensor tells the PCM to raise the idle, the PCM tells the ISC, and then the ISC is supposed to allow more air to bypass the throttle plate. A fault in any part of that circuit can cause the engine to run roughly at low rpm. It could also simply need a tune-up.

I don't know which AC sensor they are referring to and I'm not sure what the ISC is.

[us19335]

Originally Posted by johnsealey

Thanks crewzin.

i left 220 lbs of air in the system and it lost pressure over a day and a half it took me all day but i found a small leak at the pressure switch on top of the acumulator as it has a plastic nut and the o ring had been damaged so replaced that and put some pdf tape so lets see if it hold the air again filled it with another 200lbs of air as its a lot cheaper.. ha ha

so i will try and recharge it with r134 tomorrow if all is well, but i am concerned why the engine isnt raising the revs on starting the A/C. and the fan is on as soon a i put on the ignition it seems loud but i have never heard another with which to compare it.

Is it only the pcm that controls the revs or is there a sender or vacum on the compressor that could be to blame? There are no codes showing so i imagined the pcm is ok, would the relays make the fan direct, or only come on either high or low only?

At least i found a leak so im one step nearer to solving the problem, any more advice always more than welcome

cheers John

check the fan 2 speed 1 for eng. 1 for a/c comp.

[CREWZIN]

Nice of you to try and help with that old question but the thread is over a year old and the originator of the thread hasn't been back to the forum since he asked the question.

Since it's your first post, how about going to the "Welcome New PT Cruiser Members" thread and introduce yourself.