HEVAC playing up

Henrik97 · Nov 8, 2011

Hi all,
Car is a '97 P38. The AC has been out for a long time due to a leaky condenser, but otherwise the HEVAC has been working fine. Now it's developed an intermittent failure in the reading of the external temperature. It usually starts up at -40C, then after a while it suddenly goes to the correct temp. Sometimes it starts at zero and then counts down to -40 like a timer!
Any tips?

Thanks,
Henrik

Saint.V8 · Nov 8, 2011

Check the wiring and connector block to the Ambient Temperature Senser first and clean the connection faces with a good electrical contact cleaner, see if that helps.....

If you have access to a Faultmate/Rovacom/Autologic/Test Book et al....see what fault codes are indicated....

You could try replacing the ATS, as your one may have gone either high resistance or open circuit which would give incorrect readings.

If the wiring is sound, and a new senser if fitted you get similar results and no faults are indicated, then the fault may lie within the HEVAC unit....

Let us all know how you get on.

Henrik97 · Nov 8, 2011

Saint.V8 said:
Check the wiring and connector block to the Ambient Temperature Senser first and clean the connection faces with a good electrical contact cleaner, see if that helps.....

If you have access to a Faultmate/Rovacom/Autologic/Test Book et al....see what fault codes are indicated....

You could try replacing the ATS, as your one may have gone either high resistance or open circuit which would give incorrect readings.

If the wiring is sound, and a new senser if fitted you get similar results and no faults are indicated, then the fault may lie within the HEVAC unit....

Let us all know how you get on.

Thanks!
Where is the sensor located?

Saint.V8 · Nov 8, 2011

Depending on your VIN number it could be in one of two places.....

Under the Drivers lower dash apnel or in front of the Condenser under the bonnet...

Pics Attached from Manual.....

Henrik97 · Nov 10, 2011

Saint.V8 said:
Depending on your VIN number it could be in one of two places.....

Under the Drivers lower dash apnel or in front of the Condenser under the bonnet...

Pics Attached from Manual.....

That's the one on the right. Does the sensor connect directly to the HEVAC unit or does it terminate at the becm?

Henrik

Saint.V8 · Nov 10, 2011

ATS is wired into the HEVAC Unit...

Circuit Diagram attached....

HEVAC playing up

Henrik97

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Saint.V8

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Henrik97

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Saint.V8

Dyed-in-the-wool 100% RR Junkie

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Henrik97

Active Member

Saint.V8

Dyed-in-the-wool 100% RR Junkie

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