Mk1 Heater Blower not working

Dollywobbler · Post by **Dollywobbler** » Tue Nov 15, 2011 4:23 pm

Oh yes. Ideal timing. The Mk1 has decided that operating its heater fan is no longer a good idea.

When I got it, it didn't blow on settings 1 and 2, but did on 3. I understand the fault is different on these to the Mk2, so thought I'd better check what I need to do. Where should I be looking? My suspicion is switch over the blower itself.

ken newbold · Post by **ken newbold** » Tue Nov 15, 2011 4:48 pm

Fist question is, where is the blower on yours? If it's in the duct as on Mk2 cars, simply connect the two leads from the motor to the battery, if it works, it's not the motor.

Dollywobbler · Post by **Dollywobbler** » Tue Nov 15, 2011 6:06 pm

I'll have a play tomorrow. Not liking these dark evenings.

Post by **mat_fenwick** » Tue Nov 15, 2011 7:13 pm

A decent head torch really makes things a lot easier in the winter, even if it does make you look a little daft!

Not got a clue about any Mk1 differences but would advise against leaving the switch in any of the on positions in case the motor has seized. I was working on a van a couple of weeks ago where this had happened, and the current passing through the stationary motor had seemingly melted the brush holders beyond repair.

If you have no luck I'm sure we can have a look on Sunday...

Dollywobbler · Post by **Dollywobbler** » Tue Nov 15, 2011 7:30 pm

Be careful what you offer Mat! If we get too carried away, I might end up staying with you for a few weeks...

NeilGP · Post by **NeilGP** » Tue Nov 15, 2011 8:24 pm

The blower on the Mk1 is within the centre console and almost impossible for access.

From memory there are dropper resistors that regulate the speeds 1&2. These use a slider style switch that can get dirty (oxidised) and normally fixed with a clean and rebend the contacts to improve the contact.

The easiest solution is remove the slider switch cover see if you can see the contacts. This will save you a centre console full dismantle.

(On my Mk1 the bearings have given way in the motor. I ended up leaving the existing motor installed, and put a Mk2 blower in the windscreen scuttle. (not as powerful as the original, but gives me the basics))

Mothman · Post by **Mothman** » Tue Nov 15, 2011 8:25 pm

Cant really help a lot re the MK1. Mines still working[please continue]. However, with the MK 2 it was a simple earthing problem. Just cut and joined the 2 brown wires leading to it and it goes fine. Spent four years without it working though.
I hope its something similar. If it is, i would be pleased to know in case mine goes wrong.

Andy

Dollywobbler · Post by **Dollywobbler** » Tue Nov 15, 2011 8:33 pm

NeilGP wrote:The blower on the Mk1 is within the centre console and almost impossible for access.

From memory there are dropper resistors that regulate the speeds 1&2. These use a slider style switch that can get dirty (oxidised) and normally fixed with a clean and rebend the contacts to improve the contact.

The easiest solution is remove the slider switch cover see if you can see the contacts. This will save you a centre console full dismantle.

(On my Mk1 the bearings have given way in the motor. I ended up leaving the existing motor installed, and put a Mk2 blower in the windscreen scuttle. (not as powerful as the original, but gives me the basics))

Thanks Neil. I'm planning on replacing the entire dashboard at some point (Artic-steel has kindly supplied one, the existing one has holes in it!) so having to access the motor isn't the end of the world. I think the slider switch is the place to start though. My suspicion is that something is amiss there, just wasn't sure how to go about it or what to look for. I'll see if I can get on it tomorrow.

citronut · Post by **citronut** » Wed Nov 16, 2011 7:47 am

it was only the very early MK1's that had the blower behind the dash,
after that they were all the same MK1 & 2's in the skuttle below the windscreen, if the later type its probably the fan speed resistor, if so remove and try cleaning/checking for bad conections first,

its fitted in the rear face of the blower houseing at the N/S end,

regards malcolm

Dollywobbler · Post by **Dollywobbler** » Wed Nov 16, 2011 10:12 am

Ah, super. Thanks. Might go and have a quick look right now as it's actually not raining...

Dollywobbler · Post by **Dollywobbler** » Wed Nov 16, 2011 10:35 am

Bit inconclusive. I pulled out the two wires, but I'm not sure where this resistor is. Cleaned up the contacts, put them back then direct-wired to the battery. That got the fan going, but then it also ran on Position 3 when the ignition was on. So, no idea what cured it!

Would still like to get Position 1 and 2 working at some point, but not sure where the problem lies. Switch or heater blower?

citronut · Post by **citronut** » Wed Nov 16, 2011 7:40 pm

if you put you hand around the back of the N/S of the heater fan unit in the skuttle, you will find a domed gauzz/grill, this is the air intake pull the grill of towards the back of the skuttle, just past the air intake opennig you will find a device with a plug conector with wires comeing from it, the unit the plug goes into is the speed control resistor,

remove the screw that hold the top rear of the fan houseing to the skuttle, now you should be able to tilt the houseing forward to gain access to the two resistor securing screw, remove them and slide the resistor backwards out of the houseing and there youy go,

regards malcolm

Post by **mat_fenwick** » Wed Nov 16, 2011 7:54 pm

But it's NOT a resistor! I don't know about the early Mk1s, but the later system uses a transistor to control the fan speed, and this works on the principle of the speed control knob in the car varying a small current. This current is then amplified by the transistor to vary the larger current required by the motor and I can't think of a transistor failure mode that would allow full speed to work and not low speeds. (If it was resistor controlled and one had failed, then depending on the wiring layout you may only be left with only full speed).

There is a system to bypass the transistor completely with a full speed relay (as the transistor will have a drop of maybe 0.7V across it when fully 'open') but I've yet to hear about a BX that had it operational as the heater PCB in the car appears to have been modified not to operate the relay!

ken newbold · Post by **ken newbold** » Wed Nov 16, 2011 8:01 pm

You won't find the transistor and PCB mounted on the early Mk2 or in this case Mk1 cars, they didn't start fitting them till later.

Your problems are inside the car on the speed control itself.
Not sure if that's good news or not.

Post by **mat_fenwick** » Wed Nov 16, 2011 8:08 pm

So do the late Mk1s/early Mk2s have a different method of speed control than the later Mk2s? Obviously the knob in the car is different Mk1 to Mk2!