getting heater fan to work

[gazpacho andulus]

couldn't find any sort of plug and have checked the fuses. where is this plug?

[mountainmanUK]

Its a brown multi-connector that plugs into the back of the circuit board. It's quite easy to either forget to reconnect it, after taking out the board for cleaning, cut & solder modification etc. ( I did it once! )
Sometimes it can simply work itself loose while you're working on the heater control panel too.

It connects to the rear of the panel, top right-hand side of the panel , as you look at it. If you have the ignition turned on while reconnecting it, you will see the bulbs light up when it's plugged in correctly......that is, if you've got working bulbs in!!

Hope this helps
Dave

[gazpacho andulus]

thanks dave I'll try that in the morning. I'll modify the board while it's out as well
cheers
chris

[gazpacho andulus]

HI dave
I took it all apart and the connector was on so I fiddled with it a bit still no joy. PCB doesnt look burnt any where so I'm still mystified.
regards
chris

[jeremy]

Is there power available at the plug when the ignition is turned on? If not the fault lies elsewhere in the car. Is the earth to the plug sound?

Pin outs are given in Haynes - as is the entire wiring diagram.

[gazpacho andulus]

see if I can find my tester and have a look
thanks
chris

[gazpacho andulus]

The brown block has 5 wires going into it . I earthed my tester to the car body and got a light on 4 and a click from a relay behind the dash and when I touched 5 (making earth?) the blower came on. So I reckon I've got power. I plugged in the PCB and 4 and 5 were on the left looking at the PCB. At this point it aint like water ...it flows both ways... and I'm still flumoxed but slightly wiser. wadayuthink?

[mountainmanUK]

Sounds very similar to the problem I had a bit back.
I finally resorted to the "bodge method" of running a piece of wire between the two brown wires, effectively shorting them out and getting my blower to work!
I'm sure that there IS a more correct way of doing it, and I've checked out all the other threads & links regarding this subject, but this seems to work OK on Monica, and at least now I've got a working blower!

One thing that sounds different on your car is that you said you did NOT have the panel lights lit, whereas mine were lit OK but no blower.
Sorry I'm no electrickery genius! I just end up doing whatever achieves the result I need!

[gazpacho andulus]

Reckon the ....just don't know what to reckon.trouble with earthing it out is that it would't turn off. Another couple of days cogitating on it and I should have it. might need a new PCB and 5 pin male end ./
regards
chris

[docchevron]

My electrical knowledge is VERY limited so I'm no use, but if you find the PCB is FUBAR then I have a spare working board you can have gratis mate.

[gazpacho andulus]

I reckon its the PCB. I could pop up today if you're about.
or if you want to post it give me a ring and I'll give you the adress.
cheers
chris

[jeremy]

The heater circuit board is a very simple device - carrying 3 circuits - the lights, the variable speed fan control (operates through the transistor pack located elsewhere) and the high speed circuit which simply by passes the transistor pack using a relay.

There is nothing magical about the use of a printed circuit board - its simply a plastic sheet with metallic conductors attached to its surface. Wires could have been used but these cars use a circuit board - and as you can see there isn't really much that can go wrong with it.

The significant point here is NOTHING works - so the fault is probably something shared by all 3 circuits. Its unlikely that there is a fault (apart from physically sawing the board up) that will affect all circuits.

So how would I check it? - First I'd unplug it and check for:

Power in the panel light circuit (ignition on - lamps at max brightness.) Looking at the picture of the circuit board the supply is pin no 1 and the earth is pin no 2 working from the right. If current is there - then look at the board. Are the bulbs any good? Circuit is across the 2 contacts at the tip that engage with the circuit board. Wobble them in their holder - may help - but they do fail eventually.

Having got the bulbs to work there is another possible problem which is the wiper on the speed control (under the plastic disc.) This falls out easily so care should be taken. Cleaning it and the surfaces it runs on may help as well as bending it slightly to make sure it contacts well.

Its also worth examining all soldered joints round the plug on the board carefully. You are looking for cracks in the solder - and may need a magnifying glass. The solder should look consistent and shiny at all important places. I found the joints on the dimming system on the clock on my TD were dry and had cracked. Re-soldering solved the problem.

[gazpacho andulus]

new bulbs and it lit up. with ignition on I put a screwdriver across 2&3 and the blower blew...phew! When I rotated the white disc the power increased and decreased..yeehaaa! It works. Thanks to everyone for your help

[mountainmanUK]

Glad to hear it Chris! (just like the blower fan! )
That makes TWO of us who now have working fans, thanks to the advice in this fine club!

Cheers guys!