Blower Transistors

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CitroJim
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Post by CitroJim »

Yes, it is easy to take out the module.

Remove the blower assembly complete (access from up under the passenger footwell, three screws) and remove two screws to remove the motor and fan from the blower casing and the module will slip out. Everything is on push-fit connectors.

I can do a one-day turn-around. Post will not be much as the module itself is quite light and small.

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pikecrazy
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Post by pikecrazy »

Cheers , will Pm when i have time to remove and is convenient for you :wink:

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Clogzz
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Post by Clogzz »

Image Image Image

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pikecrazy
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Post by pikecrazy »

Clogzz wrote:Image Image Image
Cheers Clogzz that was going to be the next question 8)

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CitroJim
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Post by CitroJim »

Phil,

You have a PM :wink:

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pikecrazy
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Post by pikecrazy »

I would like to say a big thanks to citrojim for fixing the module , couldn't have done it with out you :lol:

Phil.

LOAC
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Hello FC Forum!

Post by LOAC »

Hello everyone! This is my first post...

I have a Xantia Desire 2.0i Automatic R reg I am trying to get sorted out so that I can sell it.

For some time, the blower motor has been stuck on full power and the only way I can control it is to take the fuse out.

I've always had the car garage serviced etc, but they wanted £140 plus VAT for a new motor as the module cannot be bought separately. As I'm selling the car, there was no way I was going to spend that!

I removed the motor and disassembled it and also did some digging on the web. It seems as if this is a major problem for Peugeots, Renaults and Citroens! It crops up on forums over and over across the world!!!

I found some good sites about repairing the module, with circuit diagrams and pictures, but they are from a Thai website:

http://www.vlovepeugeot.com/webboard/05955.html

http://www.citroenthai.org/diy/blower.html

The last one looks really good, anyone speak Thai?

So, I took the power transistors out of the module and I found that sure enough, one had gone short circuit.

It seems impossible to get hold of the FW26025A1 transistors, although as Citrojim has suggested, there is the MJ11015, or if you want to really go for overkill, the MJ11033 at 50A!

Citrojim, in another topic you said that Farnell are going to stop selling the MJ11015 and were thinking of buying up their remaining stock. I checked Farnell last night and it seems as if they are getting them now from another supplier and they have it as a stock item. RS also sell the MJ11015, but at a bit of a higher price, unless you buy 20 at a time! I have ordered a few from RS as they do not have a minimum order size if you buy online.

It's interesting to note that on the Thai websites above, they recommend using the MJ2955, which is rated at 15A. These are quite cheap, you can pick them up for less than £1.

Anyway...someone gave me a broken motor unit for me to play with and I took the module from that. It had Motorola TI829-1 transistors in it. I took out these transistors and put them in the other module and reassembled the motor. However, when I put the motor back into the car, the motor will not run at all.

I've noticed that the relay on the module seems to be activating when I turn on the ignition. From the circuit diagrams from the Thai websites, it seems as if this relay bypasses the transistors when activated.

I think what must be happening is that the thermistor disk underneath the module fell out when I was reassembling the module. I cleaned it and put it back in, but without a coppergrease coating. Perhaps the resistance of this is now too low, since now it does not have to conduct through the grease to ground?

I was wondering if someone could tell me what kind of resistance they get between the spring loaded contact on the module board and the heatsink? I get about 16 Ohms. Is this normal?

Sorry this is turning into a thesis!

Best regards,

LOAC

MikeT
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Re: Hello FC Forum!

Post by MikeT »

LOAC wrote:I think what must be happening is that the thermistor disk underneath the module fell out when I was reassembling the module. I cleaned it and put it back in, but without a coppergrease coating. Perhaps the resistance of this is now too low, since now it does not have to conduct through the grease to ground?

I was wondering if someone could tell me what kind of resistance they get between the spring loaded contact on the module board and the heatsink? I get about 16 Ohms. Is this normal?

LOAC
Hi LOAC and welcome,

Although I don't understand the electronics at your level I thought I would reply and let you know; the little metal disc (it's a thermistor??, ok :lol: ) fell out of my module when dismantled.

I simply rubbed it clean(ish) and put it back and with the new transistors I now have control over my blower again so you may be chasing a red herring there.

Sorry, I can't measure the resistance for you now as the unit is refitted in the car.

LOAC
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Blower motor

Post by LOAC »

Thanks MikeT. I've looked at the circuit again and it seems as if the relay bypasses the transistors, putting the motor on full power, so even if the thermistor is not working properly, all that should happen is that the motor should run at full power.

I changed the transistors last night to MJ11015, but still everything is dead. I get power to the unit, but it just doesn't run. Maybe one of the smaller transistors has died.

LOAC

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Clogzz
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Post by Clogzz »

The relay bypasses the transistors to spin the motor at full speed.
The transistors do the regulation of the variable speed.
If the motor is supplied, but not turning, the earth could be open.

LOAC
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motor module

Post by LOAC »

Hi Clogzz,

I get power to the module, but I only get 0.5V to the motor terminals unless I force the relay to activate, which then gives me 12V at the motor terminals.

I'm a bit baffled as to how the module is controlled. I get 10.5 V on the thermistor control line, (pin 1 of the 4way connector), but nothing on pin 3, the transistor drive input, regardless of the position of the fan speed selector on the dashboard. Is it a pulse width signal that does not register on a multimeter?

I see on one of the Thai websites:

http://www.vlovepeugeot.com/webboard/05955.html

that they have taken the module and driven it on a test bench to light a headlamp bulb. It looks like they are just using resistors to adjust the output, but it's hard to tell from the picture and I can't read Thai!

I've noticed that there seem to be 2 kinds of motor, one for the A/C model and one without. However, I have both examples, the A/C one from my car and a scrap one from a non A/C car and electronically speaking they look identical. The only difference I've noticed is that the non-A/C model uses rubber bushes to hold the motor in, while the A/C one uses a single screw in the base of the unit. Otherwise they seem the same.

Any thoughts?

LOAC

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CitroJim
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Post by CitroJim »

I wish I could read Thai too :roll:

Somehow I don't think that circuit is quite right. I cannot be sure but there is something about it that does not quite add up. Trouble is, I've never sketched one.

The realy does not bypass for full speed as far as I can recall. Rather it stops the fan running when the ignition is on but the engine is not running. The fan should only start up (at any speed) a few seconds after the engine starts. I noticed last time I tested one that the relay only operated after the engie started and remained operated for the duration.

Fan speed is controlled by the A/C ECU in AUTO mode and via the dash slider at other times. I don't think the dash slider is particularly clever, just a switched set of resistors to give variable speeds. In AUTO it won't be controlled by the thermistor (in the cabin fan) directly and I guess the A/C ECU will give a variable voltage to the module to control fan speed.

The disc is just a resistor and 18 ohms is about right. It needs a good connectin to the heatsink though and a touch of copper grease is just the job. If it is not in very good contact, this could cause the problem.

I have found a pitfall when replacing the transistors. If you apply too much solder to the emitter and base pins, a blob will form under the board unseen and this could short the pins to the heatsink. If it were one of the bases that was shorted down, this could be the cause of your problem.

Next time I have a module in for repair, I'll take the time to sketch the circuit and how it relates to the slider control.

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CitroJim
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Post by CitroJim »

Just another thought,

Are you 100% sure you have the module connected correctly?

The thick red and black motor feeds go to the two lone connection pillars on the board and the thin white wire with the black shroud around it connects to the thin black wire. Logically, it looks like the thin while wire should coonect to one of the lone pillars on the module board.

It is also possible to get the 4 pin connector the wrong way round, especially whils testing.

LOAC
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Blower Module

Post by LOAC »

Thanks for the replies Jim,

It's an interesting thought, I haven't actually started the the car while testing with the module after changing the transistors. I've just put the ingition on. I'll try it tonight with the engine started.

I think I have it connected correctly. Most of the time I have been putting the module back into the motor housing for testing. The only wire I'm not sure what it's there for is a very thin lose pink wire that seems to clip into the ground wire on the motor side. This is separate from the 4 way connector block.

When the module is in the housing with everything connected, I can feel the relay activating when the ignition is in the on position. However, with the module out of the housing, the pink wire is not connected and the relay does not activate.

Tomorrow I'm going to visit a friend who has a Xantia and I'll try the motor and module in his car and see what happens.

On the spare module I have, I've noticed that the blocking diode on the relay has gone open circiut, so any back EMF from the relay would be sent through the transistors, which is not good! It's possible that the same has happened to the module I've been trying to fix.

LOAC

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CitroJim
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Post by CitroJim »

Hi LOAC,

The thin pink wire should connect to the loose thin black wire going up toward the motor. It seems very critical to the whole operation of the module.

It's an interesing thought about the blocking diode across the realy. I must have a check of that as it may well contribute to killing the transistors. Suspension Electrovalves suffer badly from open-circuit blocking diodes but rarely if ever blow up the ECU as a result.

Mine packed up half-way through a journey. One moment all was OK and the next my blower was running at top speed.