Help please - Xantia II heater blower

[Peter.N.]

Have you checked for 12 volts across the input plug? If present make sure its still there with the fan turned on, if not it could be the under bonnet fuse box. If its the same as the XM the heater blower will only work while the engine is running. You can probably chek the motor by applying 12 v to the brushes - if its a permanent magnet motor, I can't remember, if not one connection goes to one brush and the other to the end of the field coils.

Peter

[rmunns]

Panic over!

Disassembled and reassembled again - now fan is on all the time again! Boy am I relieved! I'm ordering the bits from eBay so as to replace the trannies.

[MPV]

In my experience they die because the circuit is actually rather crudely designed and there is no effective control of current sharing between the two darlingtons. This causes one to pass more current than the other and eventually one goes open-circuit. Then with only one of the pair working, it is overloaded and eventually goes short-circuit. All this just to save a couple of low value emitter resistors which would have helped balance current sharing enormously...

Probably done deliberately so you have to buy a new module at an over inflated price. Same thing for the indicator relays which tick tick away at random after a few years due to a resistor not being fitted.

[CitroJim]

Panic over!

That's good A tip when replacing the transistors - just a smear of heatsink compound (heat transfer paste) all over the underside of each transistor is all you need; don't go mad with the stuff as too much has the reverse effect and blocks heat transfer. Also, don't solder the base and emitter leads until the transistors are fully screwed down o the heatsink.