Heater blower on full, permanently!

ktaylor21662 · Unread post by **ktaylor21662** » 08 Jul 2005, 02:34

The heater blower on my Xantia came on full today of its own accord and has stayed on full power. I've pulled the fuse now. Can someone suggest the problem here. I have a feeling it may be a fault in the blower control reostat? I've had similar problems (usually the control switch working only intermitantly) on a couple of other cars, but never got around to investigating the problem. Kevin.

AndersDK · Unread post by **AndersDK** » 08 Jul 2005, 03:35

I really doubt it would be a fault in the rheostat. This should shortcircuit all resistors and then shortcircuit the selector to a +12V line - at the same time. But you never say never with cars [:)]
If you have A/C there is a microprocessor circuit controlling the fan speed. This is more likely to fail.
What do you say guys ? Does the latest Xantia have the speed controlling transistors fitted on the motor unit - like the recent Citroen models ?
- as these are known to fail too.

Unread post by **Peter.N.** » 08 Jul 2005, 04:35

Dont know! But fan running flat out sounds suspicously like s/c transistors. Even if it doesn't have climate control there could still be a voltage control circuit driving power transistors on the motor. The newer they are the more electronics they seem to have.

zzf00l · Unread post by **zzf00l** » 08 Jul 2005, 11:24

Recent threads on this problem started by myself... transistor thingys are fitted with a circuit board and heat sink etc directly onto the motor, easy to get to and remove.. I think £30-£40 from dealer but I fancy going to Maplins and seeing if I can buy just the necessary components and put them on the circuit board myself.

zzf00l · Unread post by **zzf00l** » 08 Jul 2005, 11:27

http://www.andyspares.com/discussionfor ... C_ID=14658

Unread post by **Peter.N.** » 08 Jul 2005, 14:32

The transistors are TO3 power type, they need to be PNP and rated at 15 amps or so. They should be obtainable from most electronic component suppliers for about a couple of pounds. They are usually riveted, so you will need to drill the rivets out and replace them with nuts and bolts. I will try and find the type numbers and a supplier and post them on here.

lurchy666 · Unread post by **lurchy666** » 08 Jul 2005, 15:54

you could try what i do to mine when the heater sticks just wiggle the cables as my cables have started to burn out

Unread post by **Peter.N.** » 08 Jul 2005, 16:38

Right, I've done my research and come to the conclusion that not many people supply these transistors now, but I have found one : CPC 0n 08701 20 25 30. They have listed, 2N5880 rated at 16A for £1:66 + vat or 2N5884 25A @ £2:14 + vat, plus postage of course. I have an account with this firm but I think they will supply on a credit card order basis. The ideal transistors if you can find them are BD316/318 but I can't find anyone that lists them. Happy hunting!

zzf00l · Unread post by **zzf00l** » 09 Jul 2005, 02:37

thanks for the info Peter...I'll let you know how I get on.

guillermo · Unread post by **guillermo** » 09 Jul 2005, 02:42

Please be carefull they must be Darlington transistor.
I´ve changed that twice, here in Argentine I got some transistor of the series MJ, darlington, about 20 Amps.
My bad memory didn´t allow me to remember the number.
If i can found this data at home, I´ll send it to you.
regards

guillermo · Unread post by **guillermo** » 09 Jul 2005, 02:58

I remember.
It was MJ 11029/11031 11031 is for higher voltage.
Regards
Guillermo

Unread post by **Peter.N.** » 09 Jul 2005, 03:12

I have repaired a couple of these using ordinary bipolar transistors and had no further trouble, I'm not saying they are not darlingtons as the number on them didn't match anything I had heard of, but the resistance across the surviving junction suggested that they were ordinary power transistors.
Peter.

zzf00l · Unread post by **zzf00l** » 15 Aug 2005, 20:34

Sorted. Thanks for the info Peter. Went to Farnell InOne for 2N5884 25A they charged about £3.0 each and I bought other stuff from them to make up the minimum order charge.
Ian