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04 PT Cruiser overheating only when AC is on

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  • 2 Post By curiozities
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  #1 (permalink)  
Old 05 Apr 2015, 06:15 pm
Fresh Cruiser
Join Date: Apr 2015
Location: South Florida
Posts: 4
Unhappy 04 PT Cruiser overheating only when AC is on

Okay, hi guys. I'm a noob to this forum and here's my story.

First some basic info
  • 04 PT Cruiser
  • Normally aspirated engine (non-turbo)
  • About 88,000 original miles on it (I bought it nearly new, in 2005, with about 12K miles on it)
  • Automatic transmission

Okay, so about a year ago, my wife (the PT has actually been "her" car some years now) is driving when the engine overheats on her. The temp gauge went up, the red thermometer light came on and the dash started "dinging." She pulled over into a parking lot. We towed it to our regular shop to be safe (she has AAA).

The shop said it needed a radiator and also there was a leak around the thermostat housing. We don't have a lot of funds so we replaced the radiator and the thermostat, but didn't fix the thermo housing leak. I dealt with the leak by adding new anti-freeze (pre-blended Zerex G-05) every week.

So we stopped having overheating problems but then the AC stopped blowing cold air, right around the fall (thankfully, as we live in South Florida where you absolutely can't live without AC).

February this year, when the tax refund came in, we got the leaking housing and AC fixed (it was an electric component, can't remember which right now). All was good. But then the fan started giving us problems. So we replaced it a couple of weeks ago. After replacing the fan my wife said she noticed the car would shudder when idling.

Today, Easter Sunday, I was driving the whole family to our Easter lunch. I noticed shuddering and the AC would blow warm. Then, after half an hour of driving, the engine overheated, just as it did before on my wife (only now, my family is all there). The temp gauge went up, the red thermometer light came on and the dash started "dinging."

I immediately turned off the AC, put the heater on full blast and opened the windows. The dinging stopped, the red thermometer light went off and the temp gauge went back to normal.

We got to our lunch, then before we left, I checked the anti-freeze overflow container (but couldn't tell if it was empty or full). We drove home with the windows down, no AC (which was difficult as it already feels like summer here).

So, what can it be? Keep in mind we have a new radiator, new thermostat and new fan, all recently replaced by a reputable shop.

Given that this only appears to happen when the AC is on, could it be some module or electronic component malfunctioning? If it were the head gasket, wouldn't it overheat whether the AC was off or on? I haven't had the anti-freeze tested for hydrocarbons but for what it's worth, the oil looks like honey. Also, I tried the key-turning trick to get any problem code but all I got was "done."

If anyone can shed light on this so I can at least seem knowledgeable to my mechanic, I'd appreciate it, as we are on a super-tight budget. Thanks.
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  #2 (permalink)  
Old 06 Apr 2015, 09:33 am
Senior Cruiser
Join Date: Jun 2014
Posts: 1,665
Default Re: 04 PT Cruiser overheating only when AC is on

Hi, have your mechanic verify that the fan turns on at high speed when the AC is turned on. The fan can run at low speed and high speed and it sounds like the high speed function is not working. I realize the fan is new, but they are sometimes faulty. If it is not spinning at high speed when he turns on the AC, then he needs to troubleshoot the problem. The fan may be bad, the relays may be bad, and its possible the pcm is bad too. It is possible the thermostat is not opening fully causing a restriction that is not big enough to cause an overheat situation under normal conditions, but when the extra heat is sucked through the rad from the AC condenser, the problem is seen. This is unlikely, but possible.

Anyway I would start with the fan operation and go from there.
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Old 06 Apr 2015, 09:59 am
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Join Date: Mar 2015
Location: Gulf Shores
Posts: 35
Default Re: 04 PT Cruiser overheating only when AC is on

Please let us know what you find... Thanks
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Old 07 Apr 2015, 07:28 am
Fresh Cruiser
Join Date: Apr 2015
Location: South Florida
Posts: 4
Default Re: 04 PT Cruiser overheating only when AC is on

Thanks for the responses.

It started overheating on my wife in rush hour traffic, even with the AC off. So we took it to the shop yesterday evening.

They were able to check and make sure the fan was okay. The radiator was full. Shop advised me they did indeed put in a new thermostat when they did the radiator a few months ago.

They couldn't duplicate the overheating so they were going to try this morning. I'm out sick from work (stress over this, the job and our finances in general). Waiting to hear what the shop tells me but last night they were leaning towards a problem with the AC compressor.
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Old 07 Apr 2015, 08:02 am
Senior Cruiser
Join Date: Jan 2014
Location: SW PA
Posts: 1,358
Default Re: 04 PT Cruiser overheating only when AC is on

Other possibilities are a radiator pressure cap, and I wouldn't rule out an intermittent problem with the cooling fans as they get older, and the connector on wiring harness going to the fan motor.

If it over heats on you again, open the hood and make sure the fan is running.
Addicted to Mopar You can tell how old I am..
65 Dodge Coronet 6 cyl 2dr Post
66 Ply Satellite with 273 engine swap to 69 340 4spd
70 340 4spd Dart Swinger "Those were the days my friend"
73 Charger SE
Had a few Vetts on the way 69, 85
Several Neons some flips
01 Sebring flip
Cruiser's 01, 220K Gone to a new home
Cruiser 03 133K Gone to a new home
Cruiser 06 110K Project Gone to new Home
Cruiser 05 Ltd 120,809 bought with broken belt Oct2015
May 16 Resurrected to once again roam the streets.

20 Miles South Of Pittsburgh

Last edited by JoeX; 07 Apr 2015 at 08:04 am.
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Old 07 Apr 2015, 09:24 am
Fresh Cruiser
Join Date: Apr 2015
Location: South Florida
Posts: 4
Default Re: 04 PT Cruiser overheating only when AC is on


Just spoke with the shop. Myckee, as you noted, there can always be a problem even with a new fan. There was a short. Fortunately it's under warranty and will be replaced free.

They also found a problem with a relay which they're replacing, $32.

But... not out of the woods yet. Once they replace the fan and the relay, they're going to check the AC compressor because the mechanic believes there's some problem there and on PTs, we all know how deeply intertwined the fan and the AC are. Of course, this will all take place tomorrow, so my wife will get the the other car (also a Mopar, a 2004 Dodge Caravan) and I get to take the bus and train to work.

So myckee, again, thanks. Thanks to you too JoeX , although the fan is brand new with a lifetime warranty it still had a problem. Gulfcoast , thanks to you as well for responding. As you can see, I'm posting the outcome here for your benefit and for other readers to know what happened.

Thanks also to anyone reading this and in general to everyone on this forum as, although I'm a newbie to posting, I've lurked here for many years and have learned a lot about my PT cruiser here. Starting with the whole fan issue from years ago, which was where I learned to tell a mechanic to just check the fan (and he found out, lo and behold, it wasn't working right).

PS: I plan to post another update once everything is said and done. And I'd be remiss if I didn't give thanks to the Lord also for prayers answered!
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Old 07 Apr 2015, 07:21 pm
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Join Date: Apr 2015
Location: South Florida
Posts: 4
Lightbulb Re: 04 PT Cruiser overheating only when AC is on

Another update...

The shop called me just minutes before they closed. They were able to put in the new fan and relay today after all (they had said they wouldn't be able to do it until tomorrow).

Turns out there were some fried wires in the wiring harness that goes to the fan. They spliced it with new wires, checked the AC compressor (which their mechanic suspected was the culprit), and everything checked out a-okay.

So, it was too late for me to pick up the car today so they'll keep it and road test it tomorrow under harsh South Florida rush hour conditions just to make sure everything is fine.

So for those of you with a similar problem, check out this forum. There can be any number of things that cause your PT Cruiser to overheat. Don't rule out the fan (especially if you stop getting cold air from the AC, that's one clue you may have fan problems), and don't rule out electrical issues (including wiring) either. As others have said here in this forum, start with the cheapest/easiest solution and work your way up from there.
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Old 08 Apr 2015, 12:55 pm
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Join Date: Jun 2014
Posts: 1,665
Default Re: 04 PT Cruiser overheating only when AC is on

I am pleased you have your car all sorted out and all is well!
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a/c on, overheating

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