Heater fan issues
Discussion
I've got a couple of issues with my heater - I think they're independent but I'll explain my theory...
First off - it's a '96 with the 3 speed fan dial, now onto the problems.
1. The blower/fan only works on speed setting 3. I think this could be due to the control module under the dash - so best bet is to take the dash off and take a look? I'm expecting it may need some sort of bypass wire or similar.
2. When switched to position 3, it now blows the fuse (which is annoying as it's the same fuse that drives the gauges). I think this is probably due to a seized fan motor, so probably need to have some fun removing and taking a look at that (passenger footwell area I believe?).
Are my theories sound?
First off - it's a '96 with the 3 speed fan dial, now onto the problems.
1. The blower/fan only works on speed setting 3. I think this could be due to the control module under the dash - so best bet is to take the dash off and take a look? I'm expecting it may need some sort of bypass wire or similar.
2. When switched to position 3, it now blows the fuse (which is annoying as it's the same fuse that drives the gauges). I think this is probably due to a seized fan motor, so probably need to have some fun removing and taking a look at that (passenger footwell area I believe?).
Are my theories sound?
Just got round to looking at this.
I’ve got the old style heater control - so 4 wires in and 4 out.
12V is coming out of the connector for each of the speed settings (the medium setting is actually sending 12V through when selected and when set to 0, so I’ll have to have a look at that once I take the dash off at some point) so no issues there I don’t believe.
I set up a test circuit, putting 12V across the yellow and brown wires results in a blown fuse, so it looks like it is a seized motor on the blower that is to blame.
So I assume this means taking it out - from what I’ve read it sounds like an absolute pig of a job with the battery and carpet out...so I’m going to save it for another day as I’m not really in the right frame of mind to tackle it right now
I’ve got the old style heater control - so 4 wires in and 4 out.
12V is coming out of the connector for each of the speed settings (the medium setting is actually sending 12V through when selected and when set to 0, so I’ll have to have a look at that once I take the dash off at some point) so no issues there I don’t believe.
I set up a test circuit, putting 12V across the yellow and brown wires results in a blown fuse, so it looks like it is a seized motor on the blower that is to blame.
So I assume this means taking it out - from what I’ve read it sounds like an absolute pig of a job with the battery and carpet out...so I’m going to save it for another day as I’m not really in the right frame of mind to tackle it right now
Another year on 
and I'm looking at this again!
Just gained enough access to the motor to turn it - was a little stiff and had a couple of leaves in there...I sprayed some WD40 around and it started to free up.
I then applied 12v across the brown and yellow wires again and it fired into life!
Hooray, saves me getting it out...or so I thought!
I then tried the medium and slow fan speeds but got nothing. Only kept it on there for a few seconds at a time with a 30A fuse inline.
So...working on full speed only. I assume I'm going to have to get it out now, is it going to be something to do with the resistors?
and I'm looking at this again!Just gained enough access to the motor to turn it - was a little stiff and had a couple of leaves in there...I sprayed some WD40 around and it started to free up.
I then applied 12v across the brown and yellow wires again and it fired into life!
Hooray, saves me getting it out...or so I thought!
I then tried the medium and slow fan speeds but got nothing. Only kept it on there for a few seconds at a time with a 30A fuse inline.
So...working on full speed only. I assume I'm going to have to get it out now, is it going to be something to do with the resistors?
Steve_D said:
Which wires did you test?
I'm assuming you are testing at the plug just before the motor.
Yellow is +12V in
Ground Brown for full speed
Ground Slate or Blue for the other speeds.
Steve
Yes I'm testing at the plug.I'm assuming you are testing at the plug just before the motor.
Yellow is +12V in
Ground Brown for full speed
Ground Slate or Blue for the other speeds.
Steve
Ah, I've read in other posts that Brown was the 12v supply and the others the grounds for the speeds (yellow being fast).
Regardless, I have just tested Yellow as the 12v with the other 3 as grounds and then Brown as the 12v with the other 3 as grounds and the only time I get anything from the fan is when the Yellow and Brown wires are utilised.
In short, the Blue and Slate wires do nothing. They don't seem to blow the 30A fuse either, though I didn't keep it on for more than a second.
I'll be carrying on with this this week...
In the meantime, if I find that my heater now works on the full speed setting reliably, can I add new resistors under the dash instead, rather than taking out the motor?
If so, does anyone know what resistance I would need for the medium and slow speed?
In the meantime, if I find that my heater now works on the full speed setting reliably, can I add new resistors under the dash instead, rather than taking out the motor?
If so, does anyone know what resistance I would need for the medium and slow speed?
I've just testing the current draw on this.
Around 10-10.5A on startup. Then quickly settles to 7.5-7.8A. Does this sound normal?
Plans are to add resistors under the dash to save me getting the motor out.
I'm thinking of say, 5A for middle speed and 2.5A for slow speed...make sense?
So at 12v and 7.5A there's 1.6ohms of resistance, I think.
So if I want 5A I need to add another 0.8ohms of resistance to total 2.4ohms?
And for 2.5A its add 3.2ohms to total 4.8ohms?
I'm just assuming based on no real knowledge other than the equation so please correct me if wrong
Around 10-10.5A on startup. Then quickly settles to 7.5-7.8A. Does this sound normal?
Plans are to add resistors under the dash to save me getting the motor out.
I'm thinking of say, 5A for middle speed and 2.5A for slow speed...make sense?
So at 12v and 7.5A there's 1.6ohms of resistance, I think.
So if I want 5A I need to add another 0.8ohms of resistance to total 2.4ohms?
And for 2.5A its add 3.2ohms to total 4.8ohms?
I'm just assuming based on no real knowledge other than the equation so please correct me if wrong
Penelope Stopit said:
Unfortunately the job isn't that simple, the resistor pack relies on the air circulating around it in the air-box to cool it, you would have to fit a resistor to a heat-sink and mount a fan motor to cool it. A resistor and cooling device could be fitted up front in the engine bay, but.......
Ah OK, that's a nuisance! Can the resistor pack be replaced (easily) once the motor is out? Or is it a case of biting the bullet and getting a new motor unit.
Penelope Stopit said:
Yes the resistor can be replaced easily, the problem is that a tight motor is often the cause of resistor failure, due to the work involved you must make sure the motor bearings/bushes are good and well lubricated or fit a new motor at the same time as fitting a new resistor
If you do decide to lubricate the motor bearings you will also need to make sure the brushes have plenty of length(life)
Noted - thanks.If you do decide to lubricate the motor bearings you will also need to make sure the brushes have plenty of length(life)
Next step is get the damn thing out then I suppose!
QBee said:
Is it possible that the reason you only have speed 3 is that it takes that much ooomph to shift a fan motor that has virtually siezed bearings?
I have the mark 2 arrangement, with an alloy on/off switch for the fan than then rotates to alter the speed, rather then having three positions.
My heater fan was drawing serious amounts of current thanks to worn out bearings, so much so that it was burning out my heater control box regularly as well as making the wiring seriously hot.
New fan was fitted for me (pig of a job) and the heater matrix cleaned at the same time, as it was clogged after 108.000 miles and 19 years (actually clogged when I bought the car in 2012). I now have a proper working heater for the first time
Certainly possible, although the amp draw I'm getting doesn't seem too bad now I've lubed it all up. I guess we'll find out I have the mark 2 arrangement, with an alloy on/off switch for the fan than then rotates to alter the speed, rather then having three positions.
My heater fan was drawing serious amounts of current thanks to worn out bearings, so much so that it was burning out my heater control box regularly as well as making the wiring seriously hot.
New fan was fitted for me (pig of a job) and the heater matrix cleaned at the same time, as it was clogged after 108.000 miles and 19 years (actually clogged when I bought the car in 2012). I now have a proper working heater for the first time
So, here's the resistor - the yellow wire has actually broken off, which would explain why speeds 1 and 2 don't work...!
I still need to check if the resistor has "gone bad" or if I can simply solder it up, but if we assume it's bad - how do I source a replacement?
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