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A/C initially cuts out then works fine, what's up?

pmjolsness on Thu June 03, 2010 10:48 PM User is offline

Year: 1995
Make: Chrysler
Model: Concorde
Engine Size: 3.3L
Refrigerant Type: R134a
Country of Origin: United States

I live in Phoenix and have a 95 Chrysler Concorde. I believe it has a low side accumulator and an orifice, but I haven't checked. I have owned it less than a year so this is the first summer I've had it. It started out the A/C was working perfect. As the temps went up when I started the car up the A/C started to cool like it should, then after a short while it shuts off. And it would be quite a while before it would start to cool again. But then it would start cooling again and get perfectly cold like normal. Well this went on like this for a while, every time I put on the A/C it would cut out shortly after starting to cool and after doing that once or twice before starting to operate like it should.

It's a 15 year old car and I have no idea if it had ever been serviced. It only had 34K miles when I got it so I figured it's possible. Knowing that, I was thinking it might be low on R134a and after the little refrigerant that was in the evaporator boiled off it was taking a while for enough could be condensed and get back to the evaporator to start cooling again. So I added a can. I don't really know if it helped or not. Today it was between 95 & 100 and the car was parked in the shade when I got to it after work. I started it and the A/C started to cool, but within a 1/2 mile it cut out. I drove it for several minutes (5 - 10) when it started to cool again. And when it's hot, waiting even 5 minutes is too long! So I pull up in the drive way and hose down the condenser, it starts cooling and I drive off. I drive around for almost an hour and it's perfectly ice cold the whole time, even in stop and go traffic. When I pull back into the driveway I popped the hood, grabbed the suction line and it was ice cold. I have a feeling that had I not hosed down the condenser it might have cut out one or two more times before starting to work perfectly again. It's like it has to cut out one or more times before it starts operating normally, but once it does it's perfectly ice cold. And the hotter it gets the more times it has to cut out, and it stays off for 5 - 10 minutes, before it starts operating like normal.

Does anyone have an idea what's going on here?

Chick on Fri June 04, 2010 7:53 AM User is offlineView users profile

several possibilities, but you never should have added more refrigerant, especially without gauges, ..first make sure your electric fans are working when the ac is on...if not, that could be causing the high side pressures to rise and shut the compressor off, next could be as simple as a clutch gap adjustment.. If I were you, before you damage the system, bring it Arizona mobile air, they are in Phoenix and sponsor this board, let them check the system out for you.. With out the proper tools, you just can't fix Ac's, but you can destroy them.....

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

pmjolsness on Fri June 04, 2010 5:02 PM User is offline

I did have the gauges on when I added the can of R134a, and the fan was running. I should have noted what the pressures were, but I was in a hurry and they didn't appear excessive was all I can tell you. I might put the gauges on over the weekend and post them later. Air flow over the condenser wasn't the problem, it has cut out like that at highway speeds. Besides during the hour I drove around it was cooling fine, even during stop and go driving. I just seems to have a problem only when I first start it up, once it starts cooling there isn't a problem.

jglanham on Fri June 04, 2010 9:15 PM User is offline

I also have a '95 Concorde with a similar problem. I have traced it to a faulty pressure sensor/connector. It will randomly cut in and out. I first replaced the connector and that seemed to work for awhile. Then it started doing it again. I replaced the sensor with one from a wrecking yard and the problem went away. After a couple of years, that sensor started leaking, so I put the original one back on. Back to the intermittent problem again. When it stops working, I move the wires on the connector with a long stick and the compressor pulls in. It appears to be a faulty internal connection in the sensor. Probably should replace the sensor again, but they cost in the neighborhood of $80 - $90. Right now it's working, so I'm leaving it alone. Don't know if yours has a bad sensor, but it's something to check. Hope this helps. BTW, this vehicle uses an expansion valve, not an orifice tube. It is located on the firewall.

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johnl

Edited: Fri June 04, 2010 at 9:21 PM by jglanham

pmjolsness on Sat June 05, 2010 12:49 PM User is offline

When yours was doing this, did it only cut out when you first started it up? Cause that's what mine seems to do. Or did yours intermittently cut in and out? Because mine seems to run ok when the cooling starts working.

TRB on Sat June 05, 2010 2:22 PM User is offlineView users profile

Do you lose air volume when it stops cooling also?

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jglanham on Sat June 05, 2010 3:28 PM User is offline

Sometimes it won't work when first turned on, but moving the wires as mentioned previously, will engage the clutch. Other times, it will just quit. And again, moving the wires will get it to work. The air flow stays constant, only the compressor clutch drops out. As mentioned before, I know what the problem is, just haven't been willing to part with the $$.

My point in mentioning all of this was to point out that electronic sensors (it outputs a variable voltage and is NOT just a switch) can do weird things, and not just completely fail. Many times, sensors will have a break in a wire, component connection, etc. that will work when cold, then open up when hot, and conversely, not work when cold, but when warmed up, will expand enough to make connection. Two ways to find out...(1) Replace the sensor. (2) Use a Chrysler DRB Scan Tool to monitor it.

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johnl

Edited: Sat June 05, 2010 at 3:55 PM by jglanham

pmjolsness on Sun June 06, 2010 7:15 AM User is offline

Do you mean like if the evaporator was freezing up? No there was no loss of air flow.

pmjolsness on Sun June 06, 2010 7:19 AM User is offline

OK here’s what I saw when I put the gauges on the car. Friday afternoon when I got to the car after work, and I’m assuming it was between 95 and 100, after I started the car and put the AC on, I barely got out of the parking lot when it shut off. And it didn’t come back on. So I pull in the drive way, get the hose and hose down the condenser and it starts working. So I jump in and drive around on some of the outskirt roads and its cooling fine, that is until I get to a prolonged red light. And while waiting for the light to turn green, the AC cuts out and doesn’t come back on. So I go back to the house and hose down the condenser again and take off driving again. This time avoiding the street lights I don’t have a problem. So when I get home I put the gauges on it right away and this is what I saw:

At IDLE:Low side press – 40 psiHigh side press – 240-250 psi

At 1500 – 2000 rpmLow side press –22 – 25 psi High side press – 250-275 psi

(as the rpm goes up the high side pressure climbs until about 275 psi, either the existing fan has a high speed or there is a second fan that comes on, either way, the high side pressure drops until it gets back down to 250 psi the second fan cuts out or slows down, which ever)

That was Friday. Now on Saturday at 6 pm, it’s even hotter than Friday, about 105. So I start the car and put the A/C on. I hose down the condenser and get it cooling. Then I leave and get on the freeway and drive for an hour and it’s nice and cold the whole time.

To recap this:

When the weather was not so hot, the A/C would come on and work just fine.

As it got warmer, the A/C would cut out not long after startup and stay off for 5 – 10 minutes and do this a couple times or more before it would stay on and cool. And even so on an hour long drive it drifted in and out of cooling a few times.

Then I added a can of R134a

Now that it’s even hotter, the A/C cuts out even sooner upon initial startup, and it doesn’t come back without the help of hosing down the condenser. But once it does, that same 1 hour trip, even at a higher ambient temperature, the A/C runs nice and cold the whole trip.

Can anyone make sense of this?

mk378 on Sun June 06, 2010 9:14 AM User is offline

Do what the guy above said and see if poking at the sensor makes it start or stop. Really does sound like you may have the same problem with a flakey high side sensor. It's an expensive part to just replace on conjecture, but sometimes with intermittent problems there's no other way. There may be a way to test it by monitoring the output voltage with a voltmeter and checking if it corresponds to pressure properly.

jglanham on Sun June 06, 2010 1:05 PM User is offline

Here's something else to check. When the a/c is on, but not cooling, disconnect the clutch wire and measure the voltage from the connector to ground. Should be 11 - 14 volts. (I am assuming that you have already determined that the clutch is disengaged when there is no cooling.) If there is no voltage present, then the pressure transducer or it's connector is the most likely culprit. If voltage is present, then it would be a faulty clutch or clutch gap adjustment.

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johnl

Edited: Sun June 06, 2010 at 1:06 PM by jglanham

pmjolsness on Sun June 06, 2010 11:56 PM User is offline

I may have identified the problem. Haven't solved it yet but I think I'm headed in the right direction. I think it all has to do with the radiator fan. Not sure if it's not coming on at all or is intermittent. But this morning I was getting ready to leave the house and wanted the AC to work so I hosed down the condenser with the engine running and AC on when I noticed the fan wasn't running. I went to the auto swap meet at Glendale Community College and wasted no time getting the car moving so I had air movement over the condenser and I had AC. When I left the swap meet I waited until I was on Olive and had some speed up before turning on the air, and I had good AC all the way home. Tonight I hosed down the condenser again before leaving the house and again wasted no time getting the car moving. And when I got to a stop light I shut the AC off, but I did get into a little slow traffic and it the AC kicked off. But I waited until I got on the freeway and up to speed before I turned it back on and it started cooling immediately. And I drove for 45 minutes at highway speeds and had no problems. So I'm sure it's fan related. Now I gotta find my Haynes Manual and get the wiring diagram and figure out if it's the fan itself or the relay or a sensor.

Thanks for everyone's input. I will post what the ultimate problem was when I get it fixed, thanks again.

jglanham on Mon June 07, 2010 12:22 PM User is offline

The engine coolant temperature sensor and the a/c pressure sensor send their outputs to the Powertrain Control Module(PCM). The PCM switches the fans on through the fan relays. The Factory Service Manual contains a chart for when the fans are activated.

Fan Operation Coolant Temp. A/C Pressure
Low Speed Fan ON 210 F. 209.8 Psi.
Low Speed Fan OFF 199 F. 125 Psi.
High Speed Fan ON 230 F. 250 Psi.
High Speed Fan OFF 219 F. 230 Psi.

I would suggest hooking up your gauges to the compressor, use an accurate temperature probe adjacent to the coolant sensor, and monitor the readings to see if the fans operate when they should.

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johnl

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