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Discussion Starter #1
After almost 20 years of reliable service, the heater blower has stopped. The fuse is intact (number 16?). This is a RHD Alfa 75, TS, so I stuck my finger into the fan cage in the passenger footwell (LHS) and the cage can be moved, but it doesn't spin freely. I don't know whether it is normal.
I can't see cables to test for power. Is it the famous resistors, or likely to be the switch? Do I prepare for another day of pulling the dash?
(I searched the digest and didn't see a straight answer).

Cheers,
david - Downunder in Newcastle, Australia.
ALFA 75 TS - 240K Kms
ALFA 156 TS - 100K kms
 

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G'Day Dave,

There should be a two wire (black and red) connector coming out the back of the control panel and going to the motor. (black as usual is ground)

The resistors are under the bottom of the heater box (should have red, yellow, gray and purple wires going to it). When the fan is switched to 3, they gray wire provides power direct to the red (no resistor).

The fan should move as you described, it will not normally spin freely when flicked.
 

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Discussion Starter #3
Craig,
Thanks, as usual.
So, do I need to pull the dash to do these checks, or can it be done with everything in place?

Cheers,
david.
 

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The initial checks can be done without removing anything, ie. measure voltages or disconnect the motor and apply 12v. The resistor coils can be removed from the bottom of the heater.

Pulling the center console would be the next step (see my site).

Pulling the dash/heater (see here) is probably in your future but you may be lucky so do some tests first.
 

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Discussion Starter #5
After being head-down in the footwells this afternoon, I seem to have 12V on the grey wire at the resistors (on any switch setting), but nothing on the red wire coming from the same plate (which I assume has the resistors on the back).

Any suggestions? Do I pull that spring clip of the lower edge of the resistor plate and slide it out? It seems to me that something on that plate must now be fried.

It is a pity that the wiring diagrams don't have any colours listed against the "Q19" box. That would make things easier.

Cheers,
david
 

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G'Day Dave,


After being head-down in the footwells this afternoon, I seem to have 12V on the grey wire at the resistors (on any switch setting), but nothing on the red wire coming from the same plate (which I assume has the resistors on the back).

Ok, this makes sense. On the resistor plate there is a wire link soldered between the gray and red positions. I would bet it got too hot and melted the solder. As a test you should be able to the red and gray wires together and restore functionality. However you should pull it apart and fix it properly.

Do I pull that spring clip of the lower edge of the resistor plate and slide it out? It seems to me that something on that plate must now be fried.
It's about four years since I looked in there but I know it comes out somehow.
 

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Discussion Starter #7
It almost worked.
Sure enough, the wire that looked like it was solder stick had melted between the two posts. I replaced it with a strand of copper, replaced the resistor board, and it all worked! Eureka! The slow speed seems a bit reluctant, is there any need to spray some lube in the motor bearings (wherever they are).

And then it stopped. On a test drive, I casually turned the switch to high, and nothing. The fuse is still intact. I suspect I have knocked the resistor coils as I re-installed it.

It is too cold for furhter diagnostics today, so does anyone have any experience with this behaviour?

Cheers,
david - mobile but without heater or aircon.
ALFA75 - TS, 1989. 230000kms - heading for the track in 2 weeks!
 
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