More Heater blower problems

[peter306]

Thanks for that Jim, I've got some wiring diagrams but it doesn't say what they do, ie, 12 volts in, 4 volts out etc, so i can check continuity but not is it putting out the correct voltages.

Peter

[peter306]

Hello again,
After a bit of thought and going through the wiring diagrams I fed a 12 volt feed to the pink wire on the aircon regulator, on engine startup the blower motor started running and was working properly from the slider, speeding up and slowing down.
I remember when Taffy looked at it we did a bit of rewiring.
Any thoughts please.
Peter

[CitroJim]

This could be good news Peter. I'm sorry I've had no time to devote to this just yet but to help me a little. What pin number does the pink wire go to on the blower regulator? If you can't determine the number - it should be marked on the plug - to now what big wire it's next to will help identify it.

I'm sorry for all the delays, life is getting in the way...

[peter306]

Hello Jim, no panic, I don't use the car as much as I used to.
it's the grey plug and when the regulator is in position the wire is at the back on the right hand side, next to a thick blue wire. the numbers on the wire are 3009 and 4449.
It goes up to connector IC92A under the dash, according to the harness diagram this then connects to the fuse box with a blue wire.
I've had my multimeter on this and it seems there is no power getting to the connector.
My next step is move to the fuse box for continuity checks. I have a spare fuse box so i will probably try swapping it over

Peter

[CitroJim]

I've had a chance to look a bit into this today Peter. This appears to be the connection to the thermistor on the regulator heatsink.

I can understand if it's open-circuit the blower won't run. Putting 12v on it as a test will give a (sort-of) substitute signal to the aircon ECU.

The thermistor is there to maintain a constant blower speed against changes of heatsink temperature. I'd not recommend using the test method of substituting it with a substitute 12v feed as this may cause a thermal runaway in the regulator transistors if the heatsink becomes too hot. The thermistor guards against this eventuality.

It worth checking the thermistor spring contact. Refer to the picture below. The thermistor is a small carbon-like disc that sits on the heatsink under the circuit board. You can see the spring contact. Check the spring contact is making a firm connection to the top of the thermistor and also check with an ohmmeter between its connector pin and heatsink to measure its resistance. I'd expect t to be between 500 ohms and a couple of K ohms.

Xantia Blower Regulator PCB side.

We'll get there

[peter306]

Hello Jim,
thanks for that info, i'll check that tomorrow. I assume that is checked with no power to the board.
You'll turn me into an electrician at this rate.
On the down side, I just remounted the blower today.

Peter

[CitroJim]

Yes, check the thermistor with all power off and with the module disconnected...

On the down side, I just remounted the blower today.

Always the way Peter! And we'll issue you with your auto-electrician qualification very soon - you've well earned it!

[peter306]

Hello again Jim,
Got the multimeter on it,

that was about the average steady figure,if i slid the probe around it occasionally went higher but would settle back to about that figure.

Peter

[CitroJim]

That looks OK Peter, I can't confirm it's 100% correct as I have no modules here to compare...

Does it change with temperature?

Hmmm... The plot thickens...

[peter306]

Just warmed it up, resistance gets higher by 2 to 3 ohms

Peter

[peter306]

i'll put it back together tomorrow then, again
I am assuming that the contact strip is either pushed up or is bimetalic and makes some sort of contact with that circuit around the edge of the hole.
this sends a signal down one of the two wires to the regulator (pins 16 and 17), thats as far as i've got with it. Please correct me if i'm wrong
Also what does the separate (black) wire do.

Peter

[peter306]

don't know if this is relevant but with the ignition off is there supposed to be continuity between different fuses, checked 5 and 21 and between moving both probes i had a beep so i checked a few more with 5 and lots of beeps.

Peter

[CitroJim]

Peter, I'll look at the diagrams as soon as I have some time... I have them now all available. It may be a few hours or so...

[peter306]

Thanks for that Jim, as i said no panic, day off today, got to go shopping.
The thin Black wire from the motor does in fact turn into a thin White wire after the single connector. on the Harness diagram the three thin wires from 8045 connect to pin 16,17 and 18 on 8080, i've checked with my multimeter on continuity.

Peter

[CitroJim]

I am assuming that the contact strip is either pushed up or is bimetalic and makes some sort of contact with that circuit around the edge of the hole.
this sends a signal down one of the two wires to the regulator (pins 16 and 17), thats as far as i've got with it. Please correct me if i'm wrong
Also what does the separate (black) wire do.

The spring contact should make firm contact with the to of the thermistor Peter.

The separate black wire is a negative sense wire back to the ECU. It, along with the thermistor, is part of the speed regulation loop. The sense wire is there to compensate for small voltage drops along the main current carrying wires to the blower that would might cause speed variations.

In case you've not see them, I attach circuits of both the blower regulator and the overall aircon wiring diagram.

Thinking on, I have a feeling the thermistor in your regulator module may be faulty. Normally, in my experience, thermistors have much higher resistances than yours measures. A coolant temperature sensor, for example, is a thermistor and they typically have a much higher resistance and that changes significantly with temperature.

I'm now at a stage where I can suggest nothing more except to swap a known good aircon ECU (8080 on the circuit diagram) and blower regulator (8045 on the circuit diagram) and see if the problem resolves...

If you were at all local to me I'd be tempted to suggest you pop round and we could have a look together... Not knowing whereabouts in the UK you are I don't know how feasible that might be?