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95 E300D
154 Posts
Discussion Starter #1
My problem is that I can't stop warm air coming out of the heater. The system isnt out of control and does respond to changes of dial setting but on the coldest setting there is distinctly warm air still coming out of the vents.

Already tested:
- air con regassed and checked for leaks twice
- I have checked voltages to the duo valve which when dials are set to cold are 13.5v on all 3 terminals, when dials on hot are 13.5 on middle one and 0 on outer ones ( I think this is correct )
- cabin temp sensor and aspirator fan (both replaced)
- duo valve replaced then swopped back to old one as no improvement ( painfull ££)
- dust filter changed
- vacuum elements checked for leaks

any ideas appreciated also are there any more practical diagnostic tests I can do to track down the problem?

I still suspect the duo valve - are there any definitive tests I can do to make sure its closing fully?



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