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Full Version: Mode switch - 'heater' - no. 10 fuse blows
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Hello everyone!
Happy BTTF Day....

I've been searching for info on the a/c mode switch operation, to no avail! I have a really good electrical diagram but it doesn't seem to help in this matter.

If I turn the switch around to 'heater' it blows its associated fuse, the no. 10....

Any one narrow this down please, so I can troubleshoot?

Vin 3866
Only on 'Heater'?

The output from the mode switch goes to the Aircon Compressor and the Fan Blower switch

The A/C comes on when set to MAX, NORM and BI LEVEL and the Fan Blower is switched on at all settings apart from OFF

So a fuse blowing on just HEATER setting would suggest a fault with the mode switch contacts, or a freak short circuit at that position somehow...

You could try disconnecting a terminal from the blower motor to start with, but I really don't think that will help since, as above, the blower is powered on every setting (apart from off)
Thanks for the reply,

That's makes pretty good sense to me, so thank you for your knowledge!

I deduce then that Vent, heater and defrost are just directional choices with non aircon'd air blowing.
So I think the next plan would be to have a very close look at the mode switch and its contacts...

If they're worth it I have seen rebuild kits on Ed's Dutch website, just in case it's in a bad state!

Will let you know how it goes,
The Mode switch rebuild kit Ed sells is to replace the rubber 'maze' that controls the vacuum routing to your vent system. It may fix a hissing mode switch or non functioning vent routing. It won't fix the problem you have.

There are three brass contacts in the mode switch. They are held in position by melted over plastic studs which can break off. My first suspicion would be that one of these contacts has come adrift and is getting pushed into the wrong place when you select HEATER, causing a short.