Hi all, Heater fuse blows 10 seconds after starting the engine - fine when just ignition on - all four speeds no problem. New resister last year and new switch last week. It's a 1996 dt 2.5. It's been gradually getting worse, ie was a minute now ten seconds. Tried a bigger fuse (tut tut) still blows. Motor runs fine when connected direct to battery. Unfortunately it looks like the right hand drive heater motor has to come out from inside the car, not out the engine bay like LHD. Suggestions please? Thanks.

 

Blown fuse = excessive current. The fact that the motor runs fine when connected to the battery does not automatically mean it's okay. Put a fuse inline when you run it from the battery and see if that fuse blows.

Better yet, do that but with a meter taking an amperage measurement. Then you'll know.

Could also be a fried connector in there.

 

Thanks BlueRidge, logical and educational ideas, I couldn’t find an ammeter in my garage that went over 10amps, ran a fuse in line to battery starting with 40 then gradually dropped down. So.. blew at 15 but not 20amps - sacrificed three 15amp fuses to check this. Found a 30 auto reset fuse, this has only blown once (I think) and noticed the volts dropping to around 10v when it did happen.
What wattage is the fan and what ampage would you expect? Any other tests? I’m going to disconnect the heater under the bonnet and connect somethin to the heater leads to see if the fuse blows with this new thing connected... not sure what yet... headlight bulb maybe.

 

I don't recall the amperage on that motor,. but I'd be surprised if it's over 15. What' the standard fuse there? If it's 15 or less, that tells the story. The motor is the problem.

If it's 20, look at the connectors.

 

Hi BlueRidge - follow up - no conclusion yet -
Checking the diagrams online the blower motor fuse is 30amp - same as in my car.
I put a 30A automatic restting fuse in instead of the 30 traditional blade fuse I was using before and I've not noticed it blowing. Although I'm not sure how quickly it resets.
I also sprayed a load of WD40 into the blower with the vent open... hoping to hit the motor and lube things up a bit.
I also wiggled as much wiring as I could find - took a lot of the dash out and the HVAC sliders and checked as much wiring as I could. Found a dodgy connection or break in the door jam that effects the drivers window - need to dismantle the rubber cocertina for that.
Took the resistor out of the blower and cleaned connectors - all looks good in there.
Either the WD40 has loosened things up or the fuse is doing some sort of magic but the blowers not stopped .... and I'm on the super sensitive lookout for the smell of burning.
Dash is still hanging out and I'm happy to leave it like that for a few more weeks.
Probably try a normal fuse to test.
Also still trying to apply out Ohm's law.

 

Don'tcha just hate things that go away on their own?