2002 Dodge Intrepid Overheating Only with Air On

I have a 2002 Dodge Intepid ES 3.5 that is overheating only with the air conditioning on. The dealer, after trying to figure out whats wrong with it for a week, is telling me they think it's the heater core but are not sure. Does this make sense to anyone?

it is possible for the heater core to cause the car to overheat if it's plugged. In your case, have you confirmed that your fans come on when you turn on your A/C?

it is possible for the heater core to cause the car to overheat if it's plugged. In your case, have you confirmed that your fans come on when you turn on your A/C?

Yes, they did confirm that both fans were working. The car's temperature gauge will go up to almost 3/4, but never completely to the red with the air on, and only if it's over 100 degrees outside. Otherwise with the air off the car runs at a little less than 1/2 on the temp gauge. As soon as I turn the air off the temp gauge goes down to 1/2 again, they said there are cool spots on the radiator, which indicates a blockage? The heater also works fine.

If your temps are running at 1/2 scale normally then that could be still too hot, blocked cores in the radiator will certainly contribute to the increased engine heat as well as slow down the coolant flow through the radiator because of the blockage and causing still more heat in the engine. You might be able to have a radiator shop service the radiator by having it flushed and hopefully get the blockages removed and get it flowing again or worst case scenario might have to get the radiator replaced.

how many miles are on your '02? I have an '02 Intrepid as well, 2.7 though, and when it's idling w/ the A/C on 90+ degrees outside, the temp gauge stays about halfway, I've checked w/ my DRB III I have at my dealership and that's ok. Do you have a check engine light on? The temp. gauge in your car is controlled by the coolant temp. sensor. The reason why I ask if you check engine light is on is b/c if you have a bad temp sensor, the light will come on. When it overheats, does the water boil and steam comes from your hood? One last thing to check, while it's running, (this is a little tricky so be careful) feel the upper radiator hose and the lower radiator hose, on the driver's side front of the engine. If the lower hose is cooler than the upper hose, you have either a bad thermostat or possibly a plug somewhere in the radiator.

It has 55,000 miles on it. The car has actually never boiled over, hissed, no check engine light come on or anything like that. The temp gauge will go up to 3/4 with the air conditioning on if it's over 100 degrees outside, usually over 105-110 degrees outside. I had the cooling system checked Friday and they said that they couldn't find anything wrong with my car, they couldn't get it over 195 degrees at idle with the air on, but didn't drive it and said that 3/4 on the gauge was alright with the weather we have here (Las Vegas) and that the temp gauge doesn't go in the red. Since the gauge has never gone that high the summers before I think something is wrong. They suggested getting the temperature sending unit checked. Thanks for your help.

well, those guys are feeding you any B.S., they're correct when it's 105-110 degrees outside, your systems will work harder to keep cool, so don't be surprised to see the level go up a bit higher than normal. I know when I was in Las Vegas about a few years back, we rented a Mitsubishi Montero Sport in the middle of July and the temp gauge went a little high as well, and it was a brand new car. If the fans come on even w/o the A/C on, that means your coolant temp sensor is working just fine b/c the PCM is reading that the temp is getting hotter thus it signals the fans to come on.

The dealer also replaced the PCM in the car, thinking that, that would fix the problem and when it didn't they replaced the wiring harness for the secondary fan for the ac, but the car still does the same thing, thats when the heater core was mentioned as being bad???. The weather is going to be cooling down here in the next month or so (I hope) so I'll have to keep an eye on where the temp gauge is at over the winter or if the car goes up a mountain.

I had my car back to dealer Friday and they said that it is running at 249 degrees at idle with the air on, (100 degree weather) and that 260 degrees is overheating, that's too close for me. They admit that it is running hotter then it should, but don't know why. They say both fans are working and want to check the timing belt, they think maybe it's slipping?? This would cost $125, just to check it. I'm not sure this is the problem. Does it sound as though the thermostat could be faulty? The other day when I went to the store the temp gauge was at 1/2 when I got to the store, but after about 15 minutes in the store and returning to my car, which was turned off, the temp gauge was at 3/4 when I turned the car back on and stayed that way until I got home, approx. 4 miles with the air off. Do you know what would cause this? Thanks.

There is a product for RV's that is called "water wetter" it is an additive that makes heat transfer about 10% more efficient. You may want to try adding some to your coolant until you get your overheating problem fixed. Hopefully this will help keep the temp down a little. If you continue to run hot the head gaskets will start leaking.

I tried the "water wetter", it didn't work for me. I know this is a problem I need to get fixed, but the dealer just can't seem to figure out what the problem is. They are suggesting pressure checking the radiator now. I guess I'll go with that and see if that works.

If they pressure test it, I still think they shouuld FLOW test the radiator too, if some of them cores are plugged in there then that will drasticly reduce the flow of water through the system plus reduce the overall cooling capacity of the Radiator. They already said as stated in your second post, "they said there are cool spots on the radiator, which indicates a blockage?" If it's blocked too much then yes your car will run hot with the AC because it's cooling capacity is diminuished on it's own and the warm air being taken from the condensor in front of it further decreases it's effectiveness to remove the heat.

After everything, it turned out to be the water pump wasn't working correctly. It wasn't leaking or anything the flow through it just wasn't correct all the time.