No heat

[Steve Brookes]

I wondered how long it would be before I get a HVAC problem but now I finally have!

My cabin fans work perfectly if I turn the thermostat control to cold (blue dot) but as soon as I try and turn up the temp they stop.

Found this about cabin fans stopping in the FAQ section on the 964UK.com website:

'The most common cause for this is the rear blower not running. The Climate Control Unit in the dash monitors the air flow and if there is insufficient air pressure from the rear blower the cabin fans will be switched off. The rear blower has a dedicated 30 amp fuse (uprated from the original 25 amp part with no other changes in 1990) in the rear electrical panel together with a relay. The relay used is identical to the one (or two) fitted in the main electrical panel in the luggage compartment for the oil cooler and air conditioning condenser fans. The relays can be swapped for diagnosis purposes.'

Is this where I should start diagnosing the problem or might it be something else?

 

[chrism964]

Check the fuse in the engine compartment first. This happens to me every winter. For some reason when it's very cold the fuse blows (meaning the blower will only function on cold but I still get passive heat into the cabin) and then is fine for the next 11 months after I've changed it. Weird!

 

[Steve Brookes]

Chris that's a good description - passive heat is all that I get. I will check tomorrow. Thank you.

Also, I've just had new suspension installed which would have meant removing the blower (I believe) to access the top mounts so am wondering if it might be something as simple as something not being plugged back in by accident?

 

[chrism964]

No problem Steve. Your story sounds identical to mine.
I have replaced the 30amp fuse 3 times in the last 4 years. I can't figure out exactly what it is that causes it to blow. There isn't a consistant set of actions that causes it to happen (only when it's very cold.) Although I think my son (3) has been playing with the controls the last couple of times before the fuse has blown.
There is a fuse storage space within the rear fuse box lid. I have 3 spares in there as it only takes five minutes to check and change them.

 

[Steve Brookes]

I'm happy to report that it was just the fuse. My toes are warm again []. The blown fuse looked to be the original as it was 25 amp so have now put in the recommended uprated 30 amp fuse.

 

[colin appleton]

Steve,
When it happened to my964,The fuse was already 30amps-I had a look at the resistor which clips into the air trunking,whilst I was fiddling around because it seemed to be slightly loose.When pulled clear,it looked pretty sorry for itself,so I cleaned it up,rubbed some fine production paper between the contact sets,a quick spray of WD 40,replaced the 30amp fuse & clipped back the resistor properly.Been fine ever since.I have to say that when the heater doesn't work,£ notes initially float before my eyes until rationale clicks in.

 

[Gary C]

ORIGINAL: chrism964

No problem Steve. Your story sounds identical to mine.
I have replaced the 30amp fuse 3 times in the last 4 years. I can't figure out exactly what it is that causes it to blow. There isn't a consistant set of actions that causes it to happen (only when it's very cold.) Although I think my son (3) has been playing with the controls the last couple of times before the fuse has blown.
There is a fuse storage space within the rear fuse box lid. I have 3 spares in there as it only takes five minutes to check and change them.

If it fails when cold, it could be the fan getting a bit stiff causing the fan to draw more current ?, maybe the bearing grease is a bit gooey when cold ?