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Old 3rd October 2006, 14:55   #1
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Default Aircon and engine temperature- Inverse relation

Here is somthing that has had me puzzled for the last 6-8 odd months.

I had given my Car (Corsa 1.4) for service sometime back, and had asked them to check the AC coolant level etc. as the cooling level had gone down...

After I got the car back from service, I noticed something strange...Under stop-and-go traffic conditions, the engine temperature gauge would veer to the High side (100 C?) as it used to, but surprisingly, when I would switch on the AC, the temperature gauge would inch back to the Cool side within a few minutes :O

Anyway, I called up the Service center guys who told me that this was in fact a sign of the air-con working effectively, and this was expected behavior which I would have also seen when the car was new....

Now it has been threee years since I bought the car, and I do no remember having noticed this behavior back then...Also as I used to live in Gurgaon then (with its wide roads et-al), the engine temperature would usually stay on the cool side almost all the time so I may not have noticed this happening back then....

IS this really expected behavior? If yes, any idea why...I find it very strange as I would have expected the engine temps to go even hiher after switching on the Aircon :huh:
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Old 3rd October 2006, 15:12   #2
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It sounds like your radiator fan is not turning on when necessary! Get it checked ASAP!

I'm not sure about the Corsa, but in most front wheel drive cars (like the Esteem) with transverse engine mounting there are 2 separate electric fans near the front grille... one is fitted directly behind the radiator and the other is fitted in front / behind the AC condesnsor coil. Often there is an overlap between the AC condensor coil and radiator.

The radiator fan switches on intermittently (for about 30 seconds every 3 - 4 minutes in an Esteem) depending on the temp of the coolant. When the car is moving, air blows through the radiator and lowers the coolant temp. so the fan need not switch on as often, but the radiator fan is essential in stop - go traffic or if the car is stationary.

The condensor fan runs continuously while the AC compressor is engaged.

What seems to be happening in your car is that the radiator fan is not switching on, so the coolant is getting abnormally hot... when you switch on the AC, the condensor fan is stepping in providing SOME airflow to cool the radiator and coolant. This is a reasonable "limp home" solution, but get it checked / fixed ASAP!

- T u r b o C -
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Old 3rd October 2006, 15:27   #3
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The radiator fan is the one mounted right behind the radiator..right?
Let me check that when I drive back home tonight... with the engine gauge anything over the middle mark, the radiator fan should tay on i suppose...I'll open up the hood when I reach home and check...

Thanks!
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Old 3rd October 2006, 16:46   #4
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Does your car have one fan for both engine and AC or two separate fans?

While some cars like the Esteem and Zen have separate fans for cooling the radiator/engine and the AC condenser, others have only one. Usually, in cars with only one fan, the fan RPM goes up when the AC is switched on, in order to cool the condenser and make the AC work. Since there is only one fan, as a side effect of the increased fan speed, the engine also cools down quickly.

My FIAT Adventure though new, exhibits exactly the same heating-cooling pattern as your car and I'm told it's normal. I would suggest that you check with other Corsa owners, to get a better idea.

Last edited by directinjection : 3rd October 2006 at 16:50.
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Old 3rd October 2006, 17:52   #5
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Quote:
Originally Posted by turbo_c
It sounds like your radiator fan is not turning on when necessary! Get it checked ASAP!
No need.
Opel cars running temprature is on higher side.
The normal working temprature is anywhere between blue & red mark. (from manual)
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Old 3rd October 2006, 20:49   #6
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Hi,
This is my first post on Team-BHP.
I own a Corsa Sail 1.6 and have noticed the same thing. I attribute it to the fact that(as mentioned by direct injection & Turbo C in this thread) when the A/C is on, both the A/C Condensor & the Engine Radiator run at high speed(Corsa Radiator fan runs at 2 speeds). This dissipates the heat faster.

There is nothing wrong in this and is a normal feature. Opels run at a higher operating temperature.
If the temp needle does not cross above 75% of the range, i dont think you should worry about it.

rgds
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Old 3rd October 2006, 22:12   #7
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turbo_c: I too had a esteem LX a few years back. While what you say about the radiator fan switching intermittently is true but only when the Ac is not on. As soon as the AC comp is switched on, both, the condensor fan & the radiator fan keep running continuously..:-)

Quote:
Originally Posted by turbo_c
It sounds like your radiator fan is not turning on when necessary! Get it checked ASAP!

I'm not sure about the Corsa, but in most front wheel drive cars (like the Esteem) with transverse engine mounting there are 2 separate electric fans near the front grille... one is fitted directly behind the radiator and the other is fitted in front / behind the AC condesnsor coil. Often there is an overlap between the AC condensor coil and radiator.

The radiator fan switches on intermittently (for about 30 seconds every 3 - 4 minutes in an Esteem) depending on the temp of the coolant. When the car is moving, air blows through the radiator and lowers the coolant temp. so the fan need not switch on as often, but the radiator fan is essential in stop - go traffic or if the car is stationary.

The condensor fan runs continuously while the AC compressor is engaged.

What seems to be happening in your car is that the radiator fan is not switching on, so the coolant is getting abnormally hot... when you switch on the AC, the condensor fan is stepping in providing SOME airflow to cool the radiator and coolant. This is a reasonable "limp home" solution, but get it checked / fixed ASAP!

- T u r b o C -
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Old 3rd October 2006, 23:33   #8
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Quote:
Originally Posted by abhi182
Under stop-and-go traffic conditions, the engine temperature gauge would veer to the High side (100 C?) as it used to, but surprisingly, when I would switch on the AC, the temperature gauge would inch back to the Cool side within a few minutes
A similar experience had happened to my colleague's Indica DLX 2004 model. Eventually the problem was traced to a leaking coolant; which they fixed (the identification process having taken 1 month), and since which point of time, the problem is not present
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Old 4th October 2006, 13:08   #9
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Last night, I drove all the way home with the AC off to ensure that the engine temp gauge is high..
Opened the bonnet with the engine on, and this is what I found..

There was only one fan right behind the radiator which was spinning at moderate speeds...However, when I switched on the AC, the fan speed rose very noticeably...

I would suppose the high speed of the fan (after switching on the AC) is what is causing the drop in temps...

Anyway, even without the AC, and in bad stop-go last evening, the temp gauge stayed quite a distance from the red mark, so I suppose it really isn't a problem....

However, feedback from other Opel owners would be much appreciated
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Old 4th October 2006, 13:26   #10
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Quote:
Originally Posted by abhi182
Anyway, even without the AC, and in bad stop-go last evening, the temp gauge stayed quite a distance from the red mark, so I suppose it really isn't a problem....

However, feedback from other Opel owners would be much appreciated
Like I have said earlier in this thread.
There is nothing to worry about.

This is what my cars temprature is generally in stop and go traffic
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