Air Con: 850: Fuse in 850 Air Con System and Cooling Fan Stays On

[hal9000f]

Hi all,

luckily the Air Con works great, but I am trying to solve the cooling fan "always on in low speed" problem.

I'd like to completely turn off the Air Con to be sure it is not ON in any way and turning the cooling fan on and keeping it on forever while the engine is on.

I have searched through VADIS everywhere, and google didn't help either...

So, is there a fuse in an 850 Air Con System?

I know about the A/C relay behind the glove box, and the A/C pressure sensor and the pressure switch (pressostat)...

Is there anything else?

It's a great looking and driving 855 TDI with Manual A/C.

To solve the cooling fan problem I have checked:

- tried 3 fan relays
- tried 3 ECT sensors
- checked and cleaned all the connectors and ground
- tested the fan itself in low and highs speed
- tried disconnecting A/C pressure sensor and the pressure switch
- pulled the ECU out and checked the pins and cleaed them
- checked the temperature with Xiaotec App


When not using the A/C Cooling fan comes on in low speed only when the temperature gets to 87 C and it happens only when in city traffic or driving uphill. Temperature was never above 88 C. And then the fan stays always on even when the temperature falls to 82 C. It never fell below, it was a hot summer here. So I don't know at what temperature the fan is supposed to turn off.

When I turn off the engine, the fan shuts down, and when the engine is immediatley started again, the fan does not come on (until the temp reaches 87 C).

Does anybody know the 850 TDI temperature which should turn off the cooling fan? is it 81 or 80 C or even less?

So, please any help is welcome :-)

Thanks in advance :-)

hal9000f

[Luxobarge]

I believe that the fan is supposed to run continuously when the AC is on - just wanted to check that you know that, to make sure you're not chasing a fault that isn't actually a fault? With AC off, it should only run when the coolant temp reaches a certain level, as you mention.

[hal9000f]

Originally Posted by Luxobarge

I believe that the fan is supposed to run continuously when the AC is on - just wanted to check that you know that, to make sure you're not chasing a fault that isn't actually a fault? With AC off, it should only run when the coolant temp reaches a certain level, as you mention.

Thanks for your reply.

Yes, I know about fan running continuously (in low speed) when the AC is on.

This started to happen a while ago when my MANUAL AC is OFF,

I have this car for 16 years now, and I am sure that (when the AC was off) when temperature trigerrs the cooling fan it was always coming on in HIGH speed, ran for about two minutes, and then turn off.

But now, in the same circumstances it starts in LOW speed (instead of HIGH) and stays on until I shut down the engine.

I suspect the AC is the culprit, because when we ran the diagnostics, it showed that the AC is ON, but it was OFF. The clutch was not engaged.

That is why I am looking if there is a fuse somewhere, or if the AC relay is stuck or something...

Thanks again.

[Luxobarge]

Ah, right, understood - thanks.

Only thing I can think of is that there may be some electronics getting confused somewhere - if it were me I'd disconnect the battery, leave it for 10-20 minutes and reconnect and see if the fault is still there (in other words a full power-off and power-on reset of all the electrics). Make sure you've got the radio code before you do this of course.

This has worked for me on a few occasions when I've had odd faults with electronically controlled systems, it's free and easy so probably worth a try?

[hal9000f]

Originally Posted by Luxobarge

Ah, right, understood - thanks.

Only thing I can think of is that there may be some electronics getting confused somewhere - if it were me I'd disconnect the battery, leave it for 10-20 minutes and reconnect and see if the fault is still there........try?

Thanks again for your thoughts.

I have tried that 3 times. Twice overnight and once when inspecting and cleaning the ECU. I have even tried the ECU relearn procedure after powering it back on.

http://www.volvotips.com/index.php/8...rn-procedures/

Yes, I also believe this is some kind of electronic gremlin, that is why I have also cleaned everything I could with contact cleaner and inspected the wires.

In the beginning I also had the following Diagnostic Trouble Code reappearing:

"EFI 514: Engine Coolant Fan, low speed signal"

Strangely enough, it didn't reappear for days, but the problem still remains.

Thanks again.

[Pupbelly]

Could it be something as simple as a dodgy earth somewhere either not earthing properly or something that has gone to earth creating power to the fan?

Quite how you'd find this of course is a different matter but just my two penneth!

[hal9000f]

Originally Posted by Pupbelly

Could it be something as simple as a dodgy earth somewhere either not earthing properly or something that has gone to earth creating power to the fan?

Quite how you'd find this of course is a different matter but just my two penneth!

Thanks.

Yes, that is what I also suspect. I have already checked the fan ground, and the "overall" car and engine ground, and it's all fine.

But, I couldn't and didn't check the possible dodgy ground of the 2 wires which go from the ECU to the Fan Relay. Those 2 wires are for LOW and HIGH fan speed.

And I was hoping that it's not a problem cause it's PITA to check :-(

Would like to remove the fuse for A/C to rule that out, but it seems there is no fuse in the A/C system... Is that possible?

I will try to remove the A/C relay this weekend if I have time.

Thanks.