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Old Apr 27th, 2012, 10:46   #6
960kg
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Last Online: Dec 28th, 2022 13:25
Join Date: Jun 2009
Location: Mercville
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Quote:
Originally Posted by stephend View Post
Great how-to, Gatos - as always.

When my heater resistor went a couple of years ago, the whole ECC went haywire, randomly blowing hot, blowing cold, the blower switching on and off, air con jamming on, jamming off, stopping responding to the controls, the works. Rather than buy a complete new unit from Volvo, I bought just the transistor (the 'flying saucer' bolted to the heatsink) from Maplins, and replaced the original with the Maplin part. All of this was following a step-by-step guide that I found here on the Forum (I don't have the link handy, but I'm sure it's still available).

I notice in your introduction that the symptom you describe is solely the heater blowing air at full blast. Mine has just developed a new trick: sometimes it does exactly this. Usually, if I park up, when I start up again, everything works correctly again.

Would you say it's likely to be the resistor again?
Sadly the resistor replacement is not the end of the story!!! If your unlucky!

Some say it`s the pots on the board but rare if it is, if you put a meter across the pot contacts and move the knob the meter will give different readings so it is working ok.......i have now arrived at the fact that it is the chips on the PCB that go faulty.

Same for the blower speed. There is a relay next to the blower which if you disconnect the blower will stop for full speed as this relay is full speed only because of the power used it protects the board. I have put a good quality switch between the contacts so i can manual use full blower speed with the fascia knob turned down.

But now my heater switch is either stuck on full blast hot air or cold!!!! It is not the pots as already stated as i have changed them for good measure it is the PCB board.
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