Running Hotter with A/C

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Nick1994

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I've done more testing in this now with my Jeep. I toughed it out and drove in traffic (110 degrees out) and WITH A/C it ran at around 220-222. Once I turn OFF the A/C it goes down to 210-212 within a couple minutes. I did this multiple times driving to work today and then with the A/C on I was stopped at a light on the freeway off ramp and it jumped closer to 230. Turning on the heat and a/c off it went down to 210 after a minute or two.

All cooling components have been replaced.

What causes this? A/C blows pretty cold, compressor makes a little bit of noise but not bad. Compressor doesn't seem like it's extremely hot either. Condenser is clean.

Thanks
 
Did it start doing that or has it done it all along?

If its always done it it could be the temperature sensors proximity to the AC compressor. Compressor gets hot and warms up the temp sensor.

On a 1996 the fluid temp should be controlled with a mechanical thermostat so the engine temperature should not be load dependent.

Also check the electric fan speed through the radiator when the AC is on vs off. It could be that it is slowing down under the electrical load of the AC.
 
Maybe I'm not understanding this fully, but that seems quite reasonable. The AC is moving heat that is inside the cab, to the outside -- at the condenser. All of that heat ends up near the engine (which is also under additional load from the compressor), so a small rise in temps seems OK.
 
Originally Posted By: danez_yoda
Did it start doing that or has it done it all along?

If its always done it it could be the temperature sensors proximity to the AC compressor. Compressor gets hot and warms up the temp sensor.

On a 1996 the fluid temp should be controlled with a mechanical thermostat so the engine temperature should not be load dependent.

Also check the electric fan speed through the radiator when the AC is on vs off. It could be that it is slowing down under the electrical load of the AC.
It's been doing it for a while.

It has 2 temperature sensors. 1 at the front of the engine, not too close to the compressor in the thermostat housing. This gives the reading to the computer.

It has another at the back of the head which gives the temperature to my mechanical gauge on the dash, this is a real gauge not the cluster gauge.

I've replaced the sensors and verified with a scan tool and IR temp thermometer that the temperatures are correct.
 
Originally Posted By: Merkava_4
It's that clutch fan that's doing it. With electric fans, they run all the time with the A/C is on.
It also has an electric fan
 
Originally Posted By: KrisZ
The condenser is in front of the radiator, so when you turn on the AC, the hot air coming off of the condenser goes through the radiator next. In effect it reduces the heat removal capacity from the radiator a little bit, hence the increase in the temperature.


+1

The oil in the Forester XT is coolant-cooled. The multi-function display on our Forester XT shows oil temperature. The oil temperature, like the coolant, rises when the A/C is on, even while at highway speeds.
 
So in 110 ambient you see temps bump up 10 degrees with the AC on.

What is your thermostat? Any chance to drop it 10 degrees and give yourself a little room?

This could be a case where a bottle of Redline Waterwetter could do some good.

The Jeep is 21 years old, cut it some slack and roll the windows down! You're a native, 110 is just getting warm.
wink.gif
 
Is the gauge showing HOT ?

Have it boiled out any coolant ?

Here is my take on this . As long as the coolant is at least 50% - 50% and is circulating properly , you will not damage the engine if it has not boiled off any coolant .

Am I right ? Wrong ?

Best of luck , :)
 
Originally Posted By: Reddy45
... The AC is moving heat that is inside the cab, to the outside -- at the condenser. All of that heat ends up near the engine (which is also under additional load from the compressor), so a small rise in temps seems OK.


Originally Posted By: KrisZ
The condenser is in front of the radiator, so when you turn on the AC, the hot air coming off of the condenser goes through the radiator next. In effect it reduces the heat removal capacity from the radiator a little bit, hence the increase in the temperature.


These easily account for the few degree change you're seeing. Drive on.
 
Originally Posted By: WyrTwister
Is the gauge showing HOT ?

Have it boiled out any coolant ?

Here is my take on this . As long as the coolant is at least 50% - 50% and is circulating properly , you will not damage the engine if it has not boiled off any coolant .

Am I right ?


In terms of boiling off coolant, the radiator pressure cap is much more important than coolant/antifreeze. Roughly, for each pound of pressure the system holds, the boiling point goes up 3 degrees. So a 15 lb. cap in good condition won't allow water to boil until roughly 255 degrees if no leaks in the system.

In terms of doing engine damage from overheating without coolant boiling over, yes it is possible.
 
Originally Posted By: Nick1994
It also has an electric fan


You need two large electric fans with two speeds. Low speed comes on at 216F and high speed comes on at 221F. With A/C on, it automatically defaults to high speed.

I drive around town with the A/C on and water temp is at 176F. Ambient over 100F.
 
So 230 degree spikes are no issue?

I have major concerns of off-roading in the desert and overheating in the middle of nowhere. Or pulling my small trailer in the mountains and getting too hot.

For comparison a customer of my mechanic's has the identical Jeep, same year, even same color! His is almost always 195 degrees, same gauge.
 
Does it still have the fan shrouds? Does the fan size match the shrouds? Is the fan blade facing the right way? I don't know if it is possible on that model, but if you flip a fan blade front to back, it will still blow air the same way, but much less efficiently.
 
Cheap and easy first... clean out the radiator exterior with a garden hose. Put a bottle of lubegard cool it in the radiator, clean out the cooling system interior if dirty or neglected etc.
 
How does the shroud look?
what radiator was used?

Was the water pump replaced?
What fan setup do you have?

Its 100% normal for A/C to raise the temp 10-15f or more.

You have more load on the engine and its basically a heat mover.. moves heat from the cab right in front of the radiator.
 
1) Air is heated up by the AC condenser before it enters the radiator so the radiator is hotter when the AC is running.

2) If the temperature of a comparable vehicle is normally 195 with the AC on and your identical vehicle is 230, you probably have a clogged cooling system. Flushing may clean out the engines cooling system, but usually once a radiator is clogged internally you have to replace the radiator.

You say all the cooling system has been replaced, but how old is the radiator? If it is 10 years old or older it could be that the radiator is clogged up inside.
 
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