DaveK

If I select blue dot, the front blowers come on OK. With temp selected (or if I try defrost) it will run for a few seconds then turn off because it detects that the rear blower isn't working.

It's not the fuse (replaced it - although it hadn't blown, no difference).
It's not the relay (tried the oil cooler one, R04).

Adrians book seems to suggest that if it's not either of these, then it's either the motor or the CCU. The motor is only a couple of years old (maybe 20K miles) so it really shouldn't be that - and I think the fuse would probably blow if it was (it did last time, which is why the motor had to be replaced).

The book implies that if the temp sensor had failed, the blower would still work?

Any ideas? If it's the CCU my car is likely to join Arjans for sale!

Eric Kessel

There was a guy that found the connector inside the motor housing had fallen off...... pull the blower out (hose clamps, and the two bolts), there is a cover that the power cable goes into, take the screw off that cover, and then take a look that both leads are still attached to the motor.........

DaveK

OK, when I get the chance I'll try that. I've had the blower out before ages ago although didn't have to take the cover off.

Although - presumably, I could just unplug the connector TO the motor?
If that's getting voltage, then the problem is the motor (or connector inside).
If it's not - then I guess the problem is further back.

warmfuzzies

Jesus, failures after that "cheap" service......

seriously to see if the rear motor has failed, disconnect the overheat sensor, the one in the heater ductwork that leads from the motor/engine shroud. It should make the motor run a full tilt.

kevin

DaveK

OK. Back in 2 mins!

DaveK

Nope. Unlugged that, and fan still doesn't start up.

Adrian

Dear Dave,
Check the blower ballast resistor. You will see two spade type connectors in the plumbing far left of the engine bay.
Just because the motor was replaced 2-years ago means nothing by the way.
You can run 12V direct to the motor and see if it runs.
Removing the sensor connector will not switch it to high speed operation. The sensor connections need to be shorted for this to happen. The sensor is NTC not PTC.
Ciao,
Adrian.

Marc Shaw

Just be careful with the ballast resistor as it gets freakin' hot and will burn your finger (ask me how I know.... ). #10 below.

Some resistors can be reset, others cannot.

Marc

DaveK

How do I "check" the ballast resistor?

warmfuzzies

By check do you resistance check? bit difficult They are supposed to be about .3ohm.

you could jumper the relay contacts, I did, this is how I found one of my problems. surely you must have read some of my posts ;-))

Rancall made a damn fine contribution you could use to check for jumpering the relay here:-
https://rennlist.com/forums/showthre...ht=rear+blower

Adrian,

the resistor is only for low speed running, if dave removes no:12 in the drawing above as I did ,it should start the fan up in high speed.....? isn't this what the overheat circuit is for?

kevin

DaveK

I do remember your post - but not the outcome. I'll have to take a look at it - and I'll read Randall's. I remember he was a heating / air con expert.

DaveK

By the way - something else I noticed when I tried disconnecting the overheat sensor - my temp sensor fan on the CCU doesn't seem to be running. Guess that's just coincidence?

DaveK

I checked the resistance.

At first - I got an infinite reading. The resistor needed to be reset. I was confident it would work after that.

I shouldn't have been - because it still didn't work. Tried changing relay and fuse after resetting the resistor and it made no difference.

Reading on the resistor is about 0.8ohm. Which looks high - but Randalls post gives much higher readings so I'm a bit confused.

I think I will have to try running the motor directly first to rule that out. But that probably won't be for a few weeks - I'm away this weekend.

Adrian

Dear Dave,
How about checking to see if you have 12V on both sides of the resistor.
If you had to reset the ballast resistor this means it has been overheated which means the motor has drawn too much current. It may well be burned out but I would recommend you chase down some 12V readings and make sure power is getting to the motor.
The CCU decides when the rear blower fan is to run at high or low speed so forget this when trying to troubleshoot the system. The sensor being discussed inputs the CCU and the CCU then decides what to do and what speed to run the rear blower fan at.
Ciao,
Adrian.

warmfuzzies

Dave,

Any results yet......