CBR786

I tried searching not sure if my Final stage amplifier failed or something else .

The heater unit was working fine hot air cold air etc except the A/C which I know the A/C compressor is disconnected and the system is low on gas.

I went for a drive today and lost fast flowing hot air. The rear blower works fine. The fuse number 1 keeps blowing. I put a new fuse in and as soon as I try to to start the front cabin blowers the fuse pops also as soon as I press the front screen demist button with the fan speed set to zero the fuse pops.

I do not know why my front blowers have both suddenly died. When I reconnect fuse 1 with a new one I hear the front blowers try to go but they do not move can they both be siezed? they never made any sqeaking noises or anything so it is really strange my heating system use to work fin before. can a relay cause the fuse to keep blowing ? any suggestions welcome. I am gonna carry on searching.

ToreB

I would think you have a defective blower motor. A fault in the final stage amp for the fans motors will either stop the fans completely or just keep the running on maximum. The final stage control the two blowers in two circuits, you could try to disconnect one of the blower motors to find out if one of them is stuck or seized.
Demist button ON will start the fans at full speed regardless of the fan speed ****. See my HVAC operation details page for more on this.
Cheers,
Tore

CBR786

Thank you for quick response. I read your link very informative, I think my final stage amplifier is faulty. The unit went with out warning one minute everything working next fuse blown and no front fans. I was wondering is their any way of eliminating this final stage unit ? does any one know what the wiring the six or so wires do ? I take it some are inputs and the others are outputs to the front fans, I wanted to unclip the loom from this amplifier and disconnect the car battery and pulse live and earth signals down the relevant pins to get the front fans working. So I can eliminate the front fans and narrow it down the this amplifier. As the fuse keeps blowing when I try to turn fan speed to high setting, On low setting the fuse does not blow but the fans still do not come on even thought you can hear the rear fan coming on and increasing speed as you turn the fan speed up via the CCU. If I turn the heat button to the blue dot to stop rear fan the front fans still refuse to work. When I put a new fuse in position #1 then turn on ignition the fuse is still okay but the fan speed selector on speed zero /heat on blue dot the fans should run at low speed they do not. If I crank up the speed selector ****/dial the fans do not move on final stage I think speed position 5 the fuse blows.

CBR786

the blower motors both front ones decided to die. I tested both motors by pulsing live feed down the red wire but they just did not move. They tried to move a funny noise was heard. I tested the earth wire on the motor and that was showing a live as well. So the motor is shorted out very annoying as when the fans ran the bearing were quite and not noisy at all. I guess I will have to pull them and see what I can do to try a fix as many have tried and I think very few had success.

CBR786

okay finally got some time to work on the 964 to look at these fan motors .

Pulled the motors out both of them and the left hand motor the squirrel cage moved quite freely however the right hand one was very stiff. I think this was the reason why my fuse was blowing. I moved the cage by hand and managed to free it up. Now the motors work when I bench test them with 12 volts direct from a battery. I think I might be able to get away with trying to lube them and re fit ?

They work perfectly on the bench with no strange sounds what so ever. I did note that my car had two screws in holding the fans not torxs as others mention. my car is a 1990 LHD .

I guess I will try to lube and refit cross my fingers and hope they last

ToreB

I agree, lubricating will definetly not hurt, but it may not be a long term solution. I have seen recommendations on using lithium grease. However, brass bearings will wear over time. At least you now know the reason for the failure. :-)
Cheers,
Tore

CBR786

I managed to get my old fans working again as they where just stuck. I pulled them lubed them and refitted them a week later. I noticed that the fans are a tight fit once the plastic lid goes on top the final dust cover that is held in by the clip type springs. I will try to put a picture up. What I noticed is if you have the slightest play in the squirrel cage it will cause it to foul on the housing. I was wondering if any one ever dremmelled the housing to make it flush so that if the fan does wobble it will not get stuck

nabfa1

I wish wish wish you had taken pictures for this process ! I am going down this path oh so very soon Wish me luck ...... ny bigger then normal pitfalls please feel free to share