964 heater help required! please

[james964]

Hi

Have just bought a 1989 c4 cab which is great apart from a heater problem.

Heater was only blowing for 1-2 sec on startup then nothing. I've changed the heater control unit with a second hand unit, the fan now blows fine when setting is on cold but cuts out when the hot/cold dial is turned towards hot.

Can anyone help????

Thanks

James

[davek_964]

I did PM you, but since it's now turned into a proper post I'll answer here.

It sounds like your rear blower motor has failed - that's a typical cause of no fan as soon as you turn the temp up.
Fuse is in the engine compartment, but if it's blown that could well be because the motor is siezing.

[james964]

Ok great thanks. If it is the fan is is it straightforward to change?

[davek_964]

Fairly I think. I had mine done years ago by a mechanic - however, I've removed the blower myself since then. It's very straightforward (2 or 3 bolts).

[james964]

Thanks will try fuse first

[davek_964]

One other possible cause is the ballast resistor. If you look at the big plastic pipe on the far left of the engine bay, you'll see the connector for it on the top of the pipe. Years ago, when I had problems with my rear blower (not the time it was replaced) my resistor had tripped and I had to reset it.

Probably worth checking that (although it wasn't the actual cause of my problem. My problem was that the motor itself had been disconnected - which seemed to happen when I had the car serviced!

[Vic_S]

I replaced my blower recently after finding this useful thread on rennlist. Its an easy job...

http://forums.rennlist.com/rennforums/964-forum/46...

[james964]

Problem all sorted.

It was the rear blower fuse had blown, replaced with 30amp and all seems to be well.

This is appears to be the problem all along so I now have a spare heater control unit if anyone is interested?

[davek_964]

james964 said:

Problem all sorted.

It was the rear blower fuse had blown, replaced with 30amp and all seems to be well.

This is appears to be the problem all along so I now have a spare heater control unit if anyone is interested?

Give it a little time - the fuse usually blows for a reason. You might be lucky and it was a one-off, but it's more likely that it's a sign your rear blower is dying. I wouldn't be surprised if it blows again pretty soon.

[james964]

ok will keep my fingers crossed! It still had the original 25amp fuse but i'll prepare for rear blower problems.
Thanks for help

[Jamie Summers]

James,
I'd advise you to hang onto your spare control unit, they are temperamental beasts, and expensive to repair - useful to have a spare one ! I was looking for months to find a replacement at a reasonable price for my 964 RS ....... As the cars get older, more and more heater units are going to pack up, so you're not likely to lose any money on it if you do eventually need to sell !

Jamie

[Pope]

No offence meant, but if the circuit was designed for a 25 Amp max draw, putting a 30 Amp fuse in is not advisable. Just put a 25 Amp one in and sort the problem rather than creating more - wiring melting etc.

Just my t'penneth

[davek_964]

Pope said:

No offence meant, but if the circuit was designed for a 25 Amp max draw, putting a 30 Amp fuse in is not advisable. Just put a 25 Amp one in and sort the problem rather than creating more - wiring melting etc.

Just my t'penneth

There was a TSB (8904) which increased the fuse rating from 25A to 30A. So 30A is actually the correct fuse.

[Pope]

I'll get back in my box............