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[Pete Elite]

 If i remove the Vac pipe from the top of the HBV the heater works perfectly for a while then goes cold again, can anyone tell me what they suggest the problem could be and how to test/sort out the cause?

The car is a 96 3.0L Elite Auto with climate control.

Thanks,
           Pete .

[Pete Elite]

Any help appreciated .

[Abiton]

Possible vac solenoid-valve problem in behind glovebox + partially-clogged matrix.

Removing vacpipe from HBV ensures coolant is directed through matrix, but clogged-upness means that hot coolant flow doesn't keep up with rate of heat extraction from airflow past matrix airfins?  :-/

If the airflow gets warmer when revs (and so coolant flow/pressure through matrix) are higher this would lend support to this hypothesis.

[Malcolm_D]

Possible vac solenoid-valve problem in behind glovebox + partially-clogged matrix.

Removing vacpipe from HBV ensures coolant is directed through matrix, but clogged-upness means that hot coolant flow doesn't keep up with rate of heat extraction from airflow past matrix airfins?  :-/

If the airflow gets warmer when revs (and so coolant flow/pressure through matrix) are higher this would lend support to this hypothesis.

Where on the engine is the hypothesis and what kind of support bracket is required? 

Please help - I need to get out more! 

[Boatboy]

Hi

When you say the heater is/goes cold, do you mean the output airflow as felt at the vents or the flow and return water pipes from the matrix found up near where your left foot rests.

Steve

[Pete Elite]

The heat doesn't seem any different when engine revs. increased and the heat from the vents goes cold as does one of the pipes from/to the Matrix.

 Thanks for your replies,
                                   Pete .

[Boatboy]

With the climate set to heat can you feel any vacuum at the end of the pipe you pulled off the hbv? (answer should be no)

 If the answers yes, could a problem with the solenoid behind the glove box. Try swapping it with the one adjacent which controls the recirc flap.

If the answers no, I would suggest checking the hbv plumbing. I think it's upper pipe to the matrix iirc.


Steve

[Pete Elite]

Thanks for the advice Steve, I'll give that a try and let you know .

       Cheers,
                  Pete.