Overheating when using air conditioning

Santiago Camacho

Santiago Camacho

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Original poster
Joined
Feb 2, 2023
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Location
colombia
Ive been having the same issue for a while. Replaced hoses, radiator, waterpump with a flowkooler, thermostat for a high flow 180° one, and the car works great if the ac is off. It can take a while for it to heat up, but after driving it enough if the ac is on then it will go up to 106°C. Only with the ac on. It all seems to be an excess stress created by the ac compressor... where should i start looking?
 
Santiago Camacho said:
Ive been having the same issue for a while. Replaced hoses, radiator, waterpump with a flowkooler, thermostat for a high flow 180° one, and the car works great if the ac is off. It can take a while for it to heat up, but after driving it enough if the ac is on then it will go up to 106°C. Only with the ac on. It all seems to be an excess stress created by the ac compressor... where should i start looking?
Click to expand...

222 degrees isn't exactly overheating.

When looking at your temp gauge it's completely normal for the needle to be slightly over the halfway mark, especially on hot days with the A/C on.

That is a little hot, but again, not exactly overheating. Try spinning the fan by hand after the engine is up to full temp (and off), there should be resistance if the clutch is good. Changing the stat to a 180 deg will do nothing to lower engine temps and is not advised.

If you have an automatic transmission, a transmission cooler is an absolute must have upgrade and will remove some load from the radiator.
 
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First, your thermostat should be a 195 degree model. Going with a lower temperature thermostat does NOT help an engine run any cooler if it's running too hot. The thermostat only has two jobs.... to help the engine warm up more quickly and to help set a minimum operating temperature. You can't expect a simple device like a thermostat to help an engine run any cooler, that's strictly the radiator's job... together with a fan that is operating as it should. Stay with the factory specified 195 degree thermostat and make sure it does not claim to be "fail-safe" as some claim.

The problem is your cooling system does not have the normal reserve capacity to help keep the engine from getting too hot when there's an additional load placed on it... like the a/c or the ambient air temperature being hot. That is usually caused by running an aftermarket radiator, few aftermarket radiators have the required reserve cooling capacity for when conditions get difficult. Inexpensive online radiators have the worst reputation for sufficient reserve cooling capacity.

And radiators with more "cores" (more correctly called rows) do not cool better. The factory radiator was actually improved by redesigning it with one row vs. the two row radiators the first TJs received.

Personally I'd try to find the OEM Mopar radiator. They're getting harder to find but who knows, maybe by fluke Columbia has some Mopar radiators sitting around. The OEM Mopar radiator cools best, too bad they're now so hard to find. I was lucky to have found one to buy as a spare a couple months ago.
 
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I agree with Jerry, I just did this last summer in Texas, and my TJ was jumping to the 225-234 F range, similar to your numbers. I then put a new 195 thermostat, but also I put in Thermocure and flushed the entire system....and I found a Mopar radiator. I probbably should have gotten a backup at the time, but I just got one now, it run perfectly within range in Texas on the highway, with AC on, at 105F outside temp.

Pulling the aftermarket radiator, and cleaning the system, neither hurt, but I'm sure the Mopar radiator made the difference.
 
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Whew. Found a topic with a similar issue so I don't have to start my own.

I had an overheat warning at a long stoplight after a longer trip than usual just the other day. I had the AC on, so I turned it off, saw the gauge drop a little, then was able to get moving and it went back to normal (210). It was NOT a hot day, but NC summers are brutal and I don't want this to re-occur.

History of the jeep:
  • This jeep was wrecked when I bought it.
  • Last September, I replaced everything in front of the engine, including hoses, fan, fan clutch, fan surround, water pump, etc. during the rebuild.
  • The known weak spot is that I put in an Autozone radiator. (yes, I know - I was planning to flip the jeep at the time. If I'd known I'd fall in love and keep it, I'd have done differently.)

I did a check of everything I know to check based on what I've learned from you guys:
  1. Coolant is clear with a slight yellow tint. I don't know what brand it is, but it's not gunky or old.
  2. No evidence of any lost coolant or leaks.
  3. Oil is good. No evidence of coolant in it at all.
  4. Fan clutch stops spinning in under 3 seconds when I cut the jeep off.
  5. Again, the radiator is Autozone.
  6. There's a little dampness around the valve cover, but no significant loss of oil. When I had the first oil change done after the rebuild last September, I stupidly let Goodyear put synthetic blend in it and there's been a couple of drops per week under the jeep since then. I added some ATP Re-seal to it and it's almost stopped it.
  7. I can't tell from listening from inside the jeep if the fan is spinning faster at any particular time.
What do y'all think? Investigate the fan clutch further? Or just cut to the chase and go for the Mopar radiator?
 
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jblues1969 said:
I'm assuming this means the engine is turned off but warm, and I should spin the fan by hand looking for resistance?
Click to expand...
Yes, don't try to spin the fan when the engine is also turning it lol. When the engine is cold and doesn't need the fan the fan clutch will not be stiff, it will not force the fan to turn. When the engine is warm/hot the fan clutch needs to be stiff so the fan will spin fast "with vigor". :)
 
The only difference is the AT connectors. If you have a MT, it doesn't matter. If you have an AT, you need one that has connectors that match the ones on your Jeep.
 
Jerry Bransford said:
Yes, don't try to spin the fan when the engine is also turning it lol. When the engine is cold and doesn't need the fan the fan clutch will not be stiff, it will not force the fan to turn. When the engine is warm/hot the fan clutch needs to be stiff so the fan will spin fast "with vigor". :)
Click to expand...

So, I spun the fan when the engine was warm. It turns without a lot of resistance (I can move it with one finger) but it stops immediately when I let go. It does not free spin.
 
The fan clutch bolts onto the end of the water pump shaft. There is a tool for breaking the nut loose; your local auto parts store likely has a tool loaner program so you don't have to actually buy the tool. You purchase it, then get a full refund when you return it.
 
There are two products in that link, US Motor Works and GMB. Are they bolted or permanently attached to each other? Did you mean to buy just the fan clutch and not the water pump you're asking if you have to install?
 

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