Blower Transistors

Unread post by **CitroJim** » 28 Apr 2007, 12:48

Yesterday morning on my way to work I suffered the infamous failure of the blower motor control transistors and had an uncontrollable hurricane blowing through the car

I had a look, and sure enough, one was emitter-collector short circuit. What was more interesting is that my car had a long-standing windscreen leak in the usual place and the blower motor and controller had spent some time being rather damp. There was ample evidence of corrosion on the heatsink and PCB.

Wether or not this led to the failure or not is a moot point but it was not helping. I also noticed that Valeo had been very mean with heatsink compound when fitting the transistors originally.

Mine had the FW26025A type transistors, for which information is very hard to come by. They do however have equivilents in the MJ11015 and the 2N6287.

I have some on order from Farnell but I have had to buy six to meet the £20 minimum order conditions they impose

Not many places seem to stock them and strangely, the consumer side of Farnell, CPC, don't, even though they're the same company

Farnell have hundreds in stock.

So, if anyone wants a pair or two, let me know and you can have them at cost. As it's a bit of a tricky job fitting them (drilling out rivets etc), I'll be quite happy to fit them for you as well FOC.

I would suggest, if you have had a windscreen leak in the past, your blower may soon go into hurricane-mode and the transistors will need replacing. Use plenty of heatsink compound when you do! It may be a good idea to pre-empt their failure by changing them early. Having either a hurricane or nothing in a car on a day like today is no fun

A bit of trivia: These transistors are designed for use in high power audio amplifiers and thankfully not specifically for Citroen blower motor control

Unread post by **Peter.N.** » 28 Apr 2007, 15:24

Hi Jim

Good detection work. I believe that the original transistors are darlington pairs, but I have always used standard PNP transistors and they have worked OK. There were a while ago, lots of people having this trouble (hence my signature) so I would have thought you would have some takers.

Most of the component suppliers have either almalgamated or dissapeared now. I retired from the TV trade about 3 years ago and that's also now almost completely dissapeared.

AndersDK · Unread post by **AndersDK** » 28 Apr 2007, 17:10

Jim -

Dont get wrong on the heatsink compund. Its only used to make the transistor to heatsink heat transfer as even and effective as possible. Its not as good as pure aluminium in heattransfer. Therefore adding a layer of compound may very well worsen the matter.
Thats the reason why Valeo only used a smear of it.

Unread post by **CitroJim** » 28 Apr 2007, 20:13

Thanks Anders,

A very valid point indeed. Too much is worse than too little in this case

Basically, if when mounting the transistor on its heatsink the compound squeezes itself out from under the transistor and becomes visible around it as a bead you've used far too much

The line between too little and too much is a very fine one as we have discovered in the past with Intel P4 CPU chips. This is such a problem now that replacement chips and heatsinks come with a little syringe containing exactly the right amount of compound.

Peter, I began my career as a TV Service Engineer but could not fix one to save my life nowadays. I too miss the days when every town had a shop where you could get all the electronic bits you needed, especially to fix the radio or telly. Now we have Maplin in a few towns but it's a very poor substitute. All I can say is thank goodness for the Internet.

I'm off up to the National Vintage Communications Fair near Warwick tomorrow with a pal. We were going in the Activa but when I told him the aircon and ventilation was non-functional in it, he elected to take us in his Picasso

Unread post by **CitroJim** » 30 Apr 2007, 16:23

My new transistors arrived at 7 this morning courtesy of the Postman. Not bad considering Farnell did not get the order until 17:10 on Friday evening. I'm mighty impressed with both companies

A half-hour before work saw it all back in and working

One thing I noticed as I was reassembling was that the spade connectors on the loom and motor wiring were a rather loose fit. The responded nicely to a gentle crimp to tighten them up. Considering the currents that run around these wires, a bit of high resistance could cause overheating and more bother in the long run.

I found another possible substitute to the MJ11015 today, the MJ11033. It can run 50A of collector curent (20A for the MJ11015) but it is obsolete and the small stock I could find costs nearly £16 per transistor

Mandrake · Unread post by **Mandrake** » 01 May 2007, 00:33

citrojim wrote: One thing I noticed as I was reassembling was that the spade connectors on the loom and motor wiring were a rather loose fit. The responded nicely to a gentle crimp to tighten them up. Considering the currents that run around these wires, a bit of high resistance could cause overheating and more bother in the long run.

The fan in my car STOPPED completely due to those spade connectors on the blower motor itself. After unplugging them and plugging them back in again it was working, but the terminals were getting quite hot.

In the finish I ended up soldering the crimps in the terminals (especially on the brown plug) tensioning the terminals a bit (they were all loose) and also cleaning them with some LPS1.... no more hot terminals!

Regards,
Simon

Unread post by **lolingram** » 01 May 2007, 08:01

A transistor configuration using two transistors of opposite type (NPN and PNP) is the Sziklai pair, sometimes called the "complementary Darlington". So, PNPs would constitue a pseudo Darlington pair OK.

In reality, the appelation 'Darlington pair' is correct only when on a single chip.

Good detection work. I believe that the original transistors are darlington pairs, but I have always used standard PNP transistors and they have worked OK. There were a while ago, lots of people having this trouble (hence my signature) so I would have thought you would have some takers.

Unread post by **lolingram** » 01 May 2007, 08:19

Peter, I began my career as a TV Service Engineer but could not fix one to save my life nowadays. I too miss the days when every town had a shop where you could get all the electronic bits you needed, especially to fix the radio or telly. Now we have Maplin in a few towns but it's a very poor substitute. All I can say is thank goodness for the Internet.

Truth is that there is precious little left to repair on a 'modern' TV, other than the PSU/scan modules. I install UK SAT/TV in Provence, and over the last 15 years I have seen the virtual disappearance of repairable kit - be it TVs or satellite receivers. Textronix oscilloscope just sits on the bench these days...

Unread post by **Peter.N.** » 01 May 2007, 09:37

Hi Lol

The MJ 11015's are shown as as a pair of like polarised transistors in the data but I had replaced at least two pairs with ordinary bi polar transistors before this was brought to my attention and they worked fine, so - I dont know.

I still get the odd TV in for repair but most of the little work I get now is setting up TV/video bundles that have defeated their puchasers. I do though have a TV in my workshop at present, which has only served to remind me of how useless is all the equipment I have. I used my EHT meter to see if the line was starting up, will probably be the last time I ever use it!

ids987 · Unread post by **ids987** » 01 May 2007, 15:11

Forgive me if I'm teaching Granny to suck eggs....
I've never got around to looking at the blower motor circuitry as yet, so I'm not sure what drives the blower motor output transistors.
Regarding the Darlington vs non-Darlington, it really depends what is driving the transistors. The non-Darlingtons will require more drive. If the drive circuitry can supply the necessary current, then it will also be required to sink more current, and dissipate more power (heat). The MJ11015 have a current gain of up to 1000. Non-Darlingtons of similar rating would usually have a current gain of less than 100 - probably less than 50. Current gains of the order of 1000 from a single stage are very much the domain of small signal transistors.

RichG · Unread post by **RichG** » 12 Jul 2007, 23:12

citrojim wrote:So, if anyone wants a pair or two, let me know and you can have them at cost. As it's a bit of a tricky job fitting them (drilling out rivets etc), I'll be quite happy to fit them for you as well FOC.

Jim, do you have any of the transistors left? If so then I will take a pair off your hands.

Richard

Unread post by **CitroJim** » 13 Jul 2007, 12:44

Rich, you have a PM

pikecrazy · Unread post by **pikecrazy** » 18 Jul 2007, 14:18

citrojim wrote:Yesterday morning on my way to work I suffered the infamous failure of the blower motor control transistors and had an uncontrollable hurricane blowing through the car

This just happened to mine , is it an easy fix as i'm not electrically minded

Anybody in the Lancs region are welcomed to fix it

Unread post by **CitroJim** » 18 Jul 2007, 16:15

pikecrazy wrote:This just happened to mine , is it an easy fix as i'm not electrically minded

Anybody in the Lancs region are welcomed to fix it

No, but you're welcome to send me your blower module and I'll fix it for you and return it. I have a stock of spare transistors

PM me if you want to take me up on this

If you're not happy working on electronics then don't try yourself. There are a few pitfalls around about for the unwary. To do the job effectively you need a very good solder sucker and have to drill out the rivets holding the old transistors to the heatsink.

pikecrazy · Unread post by **pikecrazy** » 19 Jul 2007, 06:25

citrojim wrote:
No, but you're welcome to send me your blower module and I'll fix it for you and return it. I have a stock of spare transistors PM me if you want to take me up on this

Is it easy to take the module out as i will probably take you up on your offer.

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