polecat702

Ian, the heater valve opens when there isn't any vacuum to keep it closed. It's the opposite of most other cars that use vacuum to open the heater valve. If the valve goes bad it and won't hold vacuum, it stays open all the time.

Igaffz

I can't use the search function on forums to save my life!! Google finds them anyway, my main frustration is I haven't got a multimeter to trouble shoot and I've never used one so it makes it hard to find out what's working and what's not. I think I'll remove the setting motor and clean it in the morning, also I'll check the internal and external temp sensors.

Ian

Igaffz

Ok guys, today I've made progress! When laying upside down in the RH wheel well I watched the motor that operates the flap at the end of the connecting rod was trying to move when I put the temperature slider to cold but didn't seem to be able to. I removed the motor but couldn't manualy operate the flap so I gave it a hard pull and it came free, it must have become stuck through lack of use over the last year? Once this was free I decided to open the motor and clean it.


I noticed the leg on the red component had seperated from the board so I resoldered it back into place.
The other component in the corner has over heated and burnt the board at some point, will this need replacing?


After putting this all back together it now works, but is it working correctly? When the temperature slider is at the hottest setting and moved to the cold position the motor dose not move? If I pull the lever to full cold (left as far as it will go) the motor opens the flap and the blowers go from hot to cold. If I move the lever just slightly off cold the motor returns to the original position and the blowers go hot. Is this correct or should the motor work Inbetween fully open and fully closed? I hop this makes sense!

Ian

Randy V

Almost worth the price of becoming a Member.



Keep up the good work.

Hilton

Ian, while its open, replace the transistors.

https://rennlist.com/forums/928-foru...w-working.html

They're dirt cheap - should be able to get them from maplin

Igaffz

Cheers Hilton, I'll call into Maplins and replace them, I'm also going to check the condition of the external temp sensor. I'm getting there slowly!

Cheers
Ian

Igaffz

Small update. Still battling with my HVAC system, checked the external temp sensor and managed to brake the wires to the plug on the car side! Re soldered these but still no change. Suspect a faulty temp sensor or motor. Anyway at least I've got full hot or full cold so could be worse.
Had a bad power steering leak from the two pipes coming from the bottle. I've removed both and replaced the banjo washers and jubilee clips and this seems to have stopped the drips on my drive.
I've also replaced my speedo as the cog was stripped and the mileometer and tripomiter had packed up, but now working!
Gave the engine and gearbox a good degrease and jet wash to remove years of crud ready for the new gearbox/diff oil. Then the job I'm dreading, sump gasket and motor mounts.
Are the 1995 volvo 940 motor mount the ones that will fit?

Cheers fellas
Ian

Igaffz

Managed to change my gearbox/diff oil today, no problems.


Ian

Igaffz

Big news!
Removed the motor that controls the mixing flap and soldered in new transistors, I also resoldered all the other components on the board while I was at it. I'm very happy to report my heating is working perfectly, I now have hot and cold and everything Inbetween!

Replaced these with these


With these



I have to admit I didn't expect it to work so I'm very happy to tick this job off my list!

Ian

Chalkboss

Excellent! Good feeling when you can fix things like this. I'm starting to cut my teeth on more and more electrical repairs. Sort of comes with the territory with a 928...

Igaffz

Going to dig out the cruse control brain and re flow the solder when I get time, you never know it might just work!

Ian

SteveG

Randy: Poor man can't afford a meter, much less membership.
Note: you are going to have to buy some tools. One of them should be a good meter.

Bucko74

Hilton,
I have found and read this write up a few times as I need to look at my vac system also at some point before I waste time on major aircond components. Does this apply to pre S4 models or did the system change significantly with the 32V models.

I have a Euro S2 RHD

Cheers

Hilton

S2 is the same as the S4 system - same colour coding on the vac lines, same control head etc.

Bucko74

Thanks, if its the same, at least I wont be fumbling around..