I just got a 97 Intrepid. I have a question about my air conditioner. It blows cool until the fans kick on, then blows warm. It's charged, and when the fans kick on, my gauge goes to 45 to 65psi, which indicates an overcharge. But when the fans aren't on, my gauge is in the normal psi range. Could this be a sensor problem? Any help is much appreciated. Thanks in advance.

By "fans kick on", do you mean the engine fan (on the evap side)? If so, is the air flow going the correct way (drawing air into the engine)? Also some more info please i.e. the temp outside, the temp out of the duct (both when the psi is 45 and 65), ect

Yes. The engine fans. (Radiator). I can check to see if they are blowing the correct way. They should. I don't have any overheating problems. I'm in Tucson where it's in the high 90's. Coming out of the ducts, the air (when first turned on) is cool. It acts normal, getting colder as the unit is on. But when the radiator fans come on, thats when my gauge goes into the higher psi and warm air comes out of the ducts. When the fans go off, cooler air starts to flow again and the psi goes back to the normal operating range. I've also checked for error codes and found none. Which is what makes me question if there is an a/c temp sensor on this car.

Is the compressor kicking off when the fans come on (you should be able to visually check it)? Is this an after-market system, or factory? If factory, do you have the ATC (automatic climate control) or manual control? You can tell by if you have the digital temp readout on the control panel or the 3 large knobs and two buttons for the manual system.

Another thought, while I was looking at the compressor discharge pressure graph for this system, I see 45-65 range is ok if the liquid line temp is 40 deg, if it is hotter, you are probably undercharged. What is the temp of the line? Also what are you high side readings?

PS There are sensors on this car such as the sun sensor, the ambient sensor, (uses the battery temp sensor as a back up if this is failing), and the ATC in-car sensor (if you have the ATC)

No. The compressor stays on when the fans start running. The air was constantly warm this time. The fans were constantly running too. The pressure bounces from 45psi to 70psi. When my gauge reaches 70psi, it "kicks down" to 45psi. Then the gauge goes non stop back up to 70psi. When the engine is off, I hooked up the gauge and it reads a little above 70psi. (Don't know if that means anything) How and where can I check the liquid line temperature? I don't have a gauge that fits the "high" side/port. I'm doing my checking on the "low" side/port of the compressor. The car doesn't have the ATC sensor. That's the one on the top of the dash, right? There is no sensor on my dash. Where are the other two sensores located?

To check the liquid line temp, a "thermocouple probe" is used. It looks like a battery alligator type clamp used on small accessories that hook up to the battery (not as large as a jumper cable size). You could usea laser thermometer or even a meat thermometer held on with tie straps if you don't have one, it’s better than nothing. Attach/check the temp probe as close to the condenser outlet as possible. The line is the smaller line below and between the compressor and the air filter box.

The ATC sensor is either behind the small Chrysler emblem above the glove box or in the control head in some models. The sensor that sits top and center of the dash that looks like a small red plastic speed bump is the sun sensor. The ambient temp sensor is located on the inside of the front bumper (left side). It has one bolt, one electrical connector (on the top) and a “nipple” at the bottom of the sensor. The best way to test the system is with the expensive Chrysler testing equipment, but there are self tests that can be run through the car. You still have to let me know which system you have first, the manual control head or the auto (see prior post).

To help prevent the PSI from bouncing too much, try blocking off the airflow to the front grill area; it will help maintain a constant pressure by stopping the cooling fans from switching from high and low speeds.

I'm sorry. I have the manual controls. Can I buy a "Thermocouple Probe" at a local parts store? Is that the correct name? I'll search for and check on the other sensors. I'll check back later and see if you posted anything new or know of any tests I can do myself. Thanks.

Sorry, my bad, you said prior that you didn't have the "high guage". The liquid temp chart is for the high side so the probe will be of no use to you. Looking back on all you said it sounds like the system is "short cycling". Are you sure the comprosser isn't kicking off? If so, you may just be a can low. There is a check for the manual system components, thats why I wanted you to let me know as the procedures are completly diffrent.

To place the head in dig mode,
1. Start engine, the engine must be running for the entire test...do not move car.
2. Place the left knob (fan speed) to any except off.
3. Place center knob (temp) to full cool.
4. Place the right knob in defrost mode.
5. The AC button is ok on or off possition.
6. Press and hold the rear window defogger switch for 3 to 5 sec. The rear defog lamp will begin to flash, release the button when it begins to flash. The system is now in dig mode. If you wish to abort, turn the fan to off, move either of the other two knobs or press the AC or rear defog switch once.
7. The light should flash for about 30 sec and go out. The next procedure depends if the light goes out or comes on steady. Let me know.

OK. I did what you said. The system cycled through from defrost to floor to face. All hot air. After about 30 seconds the rear defrost light stopped flashing and went out. I checked the "Low/side" pressure and it topped at about 108psi, then went down to about 75psi. The rpm's also jumped from 6k to about 12k the whole time. Constantly bouncing back and forth. I did notice the condensor came on only when the psi was falling. Once it stopped falling and started to rise, the condensor would stop running. Now I'm really lost!

By condensor, did you mean compressor? Also I hope you ment 600-1200 RPM, not 6000-12000!!! First tell me, did you try to add a can? So far as the test is concerned, the control head has been checked, and a cal has been done on the system. The next part involves a lengthy procedure and before I type it out, I'd like to ensure you have charged the system asit sounds like it's short cyc. Not only, but the next test checks every little detent possition of your knobs, and from your problem I don't think that will be of much use.

Yes. I meant compressor. Also the rpms 600 to 1200. Tried to add a can in the beginning, (Which is what I thought it only needed) It didn't work. That's when I started to look at trying to figure out what was going on and why I couldn't charge it. The gauge on the can is the gauge I've been using to come up with the psi numbers.

ok, but the numbers have changed since you added the can. It may be you have a leak and you are now low again (from the original point seeing the PSI has also changed along with the more serious lack of cooling). If so, you need to find the leak and fix before you go on. If you don't, eventually you could deplete the oil from the system and burn out your system which will cost more in the long run. How long was the system operational before you added the can (was it fucntioning)? Are you familiar with cooling systems or is this a newer venture? I only ask because I made some assumptionns from the start that may be leading/causing more trouble than it should be.

When I first bought the car, it would blow hot about 90% of the time. It would blow cool (not real cold) When the psi was dropping. I tried adding a can, because I thought it was low. That's when I first saw the psi numbers and they were in the yellow area (45 to 65psi). The blue (ok) area on the gauge is 25 to 45psi. I now see on the side of the gauge that there is a sticker that says if it's in the yellow it could be overcharged. Could that be why after we did the dig mode the psi went really high? I doubt if there is a way I can let some out so I can get the psi down. Could this be my problem (overcharge) from the beginning, and the psi went higher because I originally started to add a can and it was already overcharged? And yeah, A/C is a newer venture for me.

When you added the can, what type of freon was it (R12 or 134a)? When you added the can, did you invert it? If not, you may have done a "vapor charge" only, and not added the other contents of the "blend" in the can. If so, the system should be completly depleted and recharged. Also, if there is/was a leak, the line oil may be low. There is no way to measure this though and the shop manual has a procedure to drain and refill, but once again you don't have the eq. (need to pull a vac on the system if the lines have been opened).

P.S. AC is a new venture for me also, I am getting most of this advice for you through a friend of mine who has been a AC tech for 15 years (the rest from the shop manual). His suggestion was basicly a start from scratch because you can't tell what is going on without the proper equipment (the high side guage and temp probe). It may be best if you just bring it to someone with the proper equipment (and cheaper in the long run).

Ok. Got it going. The problem was that it was WAY overcharged. We drained it compleatly and filled it with new freon. It works good. Thank you for all your help.

I'm glad to hear it's up and running!At least it's fixed before the really hotest part of summer started!