AC causing engine to overheat?

Okay, I have a 97 Intrepid with the 3.5L V6.

The engine recently started overheating, so I did all the logical things, checked coolant levels(okay), replaced thermostat(no change), no damage to hoses or anything like that. Also checked the fan, both cycle on/off as expected.

What I discovered was, when traveling at highway speeds, the engine was running slightly warmer than usual, but still well within what would be considered normal. However, when stuck in traffic, the engine temp quickly rises to the point of boiling over.

The discovery I made by accident the other day, is when the engine begins to overheat, by turning off the AC, the temp quickly comes back down to normal.

This morning I did some testing, and I cranked up the car and let it idle for about 15 mins w/o the AC on, and I touched the engine radiator, and it was barely warm to the touch.

Then I turned the AC on max, and I quickly noticed a substantial increase in the amount of heat being blown out of the engine. So I again touched the radiator, still barely warm, but when I touched the AC condenser, it almost burned my hand.

So my theory is that the AC condenser is getting so hot, it is causing the engine coolant to heat up, rather than cool down.

so what would cause that much heat to be generated by the AC?

is it possibly something as simple as being low on coolant or something worse?

Any suggestions would be much apprciated.

To understand A/C, you have to know that refrigerant goes through two states of matter, hot and cold and also liquid and vapor. When refrigerant enters your condensor, it is a high pressure vapor and leaves as a high pressure liquid or, in simpler terms, a hot gas and leaves as a hot liquid. First, I would do is check your condenser and see if you have any bent fins, bugs, etc. A clogged condensor can overheat. Also, go to a service shop and have your system tested to see if it is overcharged or restricted somehow. If your cooling system is intact, then chances are, you have a restriction somewhere in your A/C and it is causing it to run hotter than normal.

Just a thought, but have to noticed if the fans are running during all of this? They should be and both of them. I was just thinking that it's possible that the reason it's getting so hot was either one fan wasn't working or just not turning fast enough. These cars have 2 speeds on the fans and 2 relays in the power distribution box under the hood, one relay is for high speed and one is for low speed. Might want to check it out.

Thanks moparmadness...

I did some looking at the fans and I'm not 100% certain how they are supposed to opperate, but what I noticed when I checked the, is it appears that only 1 fan turns on at a time.

I swapped the hi/low speed relays and it appears to change the fan that rotates.

So, are both fans supposed to turn and both have hi/low speeds, or does it turn 1 fan on for low, and both fans on for high?

I suppose replacing a relay will be really easy now that I've replaced the radiator.. heh

Thanks for the suggestion!!

It's my understanding that they both run when they run but they run faster on Hi/Speed That seems kind of different that what most would think I guess but I'm pretty sure thats how they operate. I would bypass the relays and just see I guess I really don't have a solid answer sorry, but I'm pretty sure they both run on both speeds.

Well.. it appears the fan motor was the problem.. apparently 1 fan is strictly a low speed fan, and the other is a 2 speed fan... the 2 speed fan was partially fried.. it didn't run at all on when the low speed relay was on, and when the high speed relay kicked in, it only turned at the low speed rpm..

Got a new fan motor and it works like it should.. no more overheating either..

Thanks guys!!

[QUOTE=Fenrus]Thanks moparmadness...

I did some looking at the fans and I'm not 100% certain how they are supposed to opperate, but what I noticed when I checked the, is it appears that only 1 fan turns on at a time.


QUOTE]


I think Both of mine run at the same time on my 99

Hi i have a problem with my 93 vision. It seems evry 3 months or so it overheats. The first time i changed the termostat and the car ran great until it started again. Second time i put in new headgasket, radiator. Thought that would be it but guess what again this morning it overheated, i'm in new brunswick canada and it's like minus a gazillion here (freezing). The garage say's the thermostat was stuck open. I figure something triggers this. Any suggestion please thanks. I enjoy the car but if it keeps breaking down evry 3 months.... Oh by the way i have a command start could it be part of the problem

Hi i have a problem with my 93 vision. It seems evry 3 months or so it overheats. The first time i changed the termostat and the car ran great until it started again. Second time i put in new headgasket, radiator. Thought that would be it but guess what again this morning it overheated, i'm in new brunswick canada and it's like minus a gazillion here (freezing). The garage say's the thermostat was stuck open. I figure something triggers this. Any suggestion please thanks. I enjoy the car but if it keeps breaking down evry 3 months.... Oh by the way i have a command start could it be part of the problem

If your thermostat was stuck open, the car wouldn't overheat, actually, it would do the complete opposite, it would overcool. When you're driving down the road, do you sometimes see a haze that covers the windshield and smells like anti-freeze coming from the air vents? If not, check ALL your hoses; make sure nothing is kinked, bound, or blown.

sorry i meant my termostat was stuck closed. Also this time i couldn't shut the car off, but after greasing a bit the shift gear it now works fine. This time i put in a termostat from the dealer maybe it will help. In 3 three months from now hopefully it won't start overheating again. I was thinking about unpluggin' the ac cause i read they sometimes make the engine run a bit hot. The dodge dealer day's that the car does work a bit hotter but within the norm. I'll check the fans, they both work but maybe if i put them on high. Any idea's Thanks mickyandre