How to Replace the Heater Resistor

[Pete_c20]

Be worth checking if the fan should be on full when set to max. ie when set to full is the resistor is bypassed? If so it only running slightly when set to max might not be down to your resistor.

[choosy54]

So,,,,,,,,,,,,,this post has answered another of my queries. Thanks guys for such an in depth discussion on a problem that WILL crop up on another owners Volvo.

[druid]

Originally Posted by choosy54

So,,,,,,,,,,,,,this post has answered another of my queries. Thanks guys for such an in depth discussion on a problem that WILL crop up on another owners Volvo.

nice too see this 1.8 GDI estate. 215,000 miles so far and still going strong.
I have 166,000 so good to see other Gdi high milers. Gatos keeps us rolling!

[dmiller]

Originally Posted by Pete_c20

Be worth checking if the fan should be on full when set to max. ie when set to full is the resistor is bypassed? If so it only running slightly when set to max might not be down to your resistor.

Its not bypassed when set to max, at least it certainly wasn't on my phase 2 V40...

So yesterday morning we went to take our daughter out, fired up the volvo and couldn't demist the windows as the blower wouldn't turn on at all. The fans all worked last time it was used but wouldn't turn on at any speed at all. Annoying, so the volvo was parked and we used my wifes boring kia yesterday.

Once my daughter was off to bed last night I started to dismantle the dash so I could find out what was faulty. Fuses all fine so no easy fix. I didn't go straight to the resistor as I had no fan spinning at all. Out with the heater control unit and the potentiometer was checked, all ok. Connected 12v to the motor, it spun up fine. Checked and no voltage at the motor but 12v at the resistor pack. I still wasn’t sure if it was the resistor pack as I would expect to be getting the fan working on 6 on the control unit but I decided to bypass the resistor unit. I did this by shorting the two bottom pins on the connector for the resistor, as shown here:

Ignore the thin wire that’s for the dab antenna.

My Haynes book has 4 wires going to the resistor unit but my car just had three - I think the haynes book is based on the phase 1 for some of the wiring diagrams as they don’t always match my car.

Anyhows - shorting out the resistor connector got the fan going full speed so it was looking like it was the resistor pack that was faulty. I checked my local scrappy but all their phase two cars were missing them or looked to be in worse shape than the one I took out... A bit more googling found that the MJ802 transistor was available from Maplin. So off I went with the daughter and bought one of these:
http://www.maplin.co.uk/p/mj802-stan...to3-case-n03aj
If your buying them elsewhere you need to make sure that it is in case TO3 as thats a straight replacement and fits the heatsink. My local Maplin had two in stock and the guy seemed to think most maplins would have one or two in stock.

The old transistor was held in with two screws (fiddly) and also it was crimped to the cables and then heat shrunk over the crimp. The easiest way I found to fit the new one was to use a stanley to cut away the old heat shrink and use pliers to remove the old crimps then solder then heat shrink some cable to the fittings on the transistor then screw it in place (with some thermal paste) and solder the new cables to the cables on the heat sink assembly. The cables were too short for anything else.

Once the whole assembly was back together and tested I had all 6 fan speeds back, in a nice range from gentle tickle to strong gust. It must have been going for a while as when I sat it at 6 it happily blew all the dust out the vents onto the dashboard... Still not a bad fix for less than £6.

Thanks again Gatos for the great guide to dismantling to get at it - its a top tip to remove that bolt to pull the dash forwards to get in there!

Cheers,

David.

[coffeejunky]

The post above reminded me to share the supplier I used when I replaced mine.
The correct transistor is available for just £2.36 delivered on eBay.
Seems a quality replacement as it is still working brilliantly over 6 months later.
eBay link:
http://www.ebay.co.uk/itm/MJ802-Tran...E:L:OU:GB:3160
Alternatively, if this link is ever down, the seller was littlediode_components and you can find it on their store by searching for MJ802. Came very well packed too

[blairs40]

so I will try and find my original post on my fan not working ... and give the answer there as well , ... if the fan on the phase 1 cars doesn't work on 1,2,3,but does on 4 then it is most likely your ceramic resistor .... if however like me , no fan on any speeds , but every so often would work for no reason , then I suggest you replace the relay in the drivers side just above the internal fuse box .... I could turn my fan on , ,,,,,nothing then all of a sudden it would work , then not work .... replace the $5 nzd relay and now back to working on all settings , just one more thing to check chaps ...not always the resistor ....
[IMG][/IMG]

[ma70]

Just another thought on sporadic/random heater & aircon activity where it gets "a mind of it's own" (or the "Christine effect" lol).
I've read in some posts from way back on here & other forums that far from being dry joints or faulty ECC/AC control units, the problem could be as simple as the contacts on the multiplugs getting dirty/loose over time. Worth a shot cleaning & carefully bending the contacts back out with a toothpick or similar if you have crazy climate syndrome

[Julielizzy]

Awesome guide, thank you so much. It only took my gorgeous 2 year old assistant and I 45minutes x x

[gatos]

Originally Posted by Julielizzy

Awesome guide, thank you so much. It only took my gorgeous 2 year old assistant and I 45minutes x x

Glad I could help

[Liam1973]

I to have a problem with the Heater Motor Resistor, if it doesn't work, how much is a new PCB.
Also the immobiliser light stays on. The car starts no problem. Is this a common issue with Volvo S40?