Engine fan running on mk6 125

[Mark94]

AHA!!!!

Unplugging the HIGH PRESSURE AC switch (at bottom of engine, on pipe, next to intercooler, and the fans stop.
Plug it back in, fans start.

As noted, with fuses 10 & 225 removed (and AC light not coming on and thus disabled), the symptoms remain - so it must be the ECU earthing rather than power going via it.

So will unplug that and leave AC off for now till I work out how to swap it - watch this space!

Without the help of everyone with the info and explaining the switches I'd not have considered or tested it. Thank you very very much.

I'll see how to change that, but guess it may be a garage job to recharge the AC system.

[wojciech]

Hm... You have untypical extra fuse box on the wheel arch.
I have different fuse box, all relays are definite AR1 to AR10. My van is 2003.

Relay AR7 is for fans high speed. I have it.
AR2 and AR4 work for left and right direction indicators. AR3 is... empty (spare socket).

If you have only two small relays, where is relay for high speed in your van?

AHA!!!!

At last...

[Mark94]

That circuit diagram does not give any hint of why/how removing the high pressure switch connector would make the fans go off!
Esp with fuses 10 & 225 removed...

But it does.


And yes, no high speed relay fan. Where did that go!?! Its been like that since new I expect. Temp has never ever moved above halfway, even in v v hot weather. Guess the AC is on and that fan is enough.

My van is a late Mk6 so who knows what they did.

[wojciech]

And yes, no high speed relay fan. Where did that go!?!

Maybe in last models it doesn't exist. Practically two fans with lower speed it is most often enough...

Maybe you have to much refrigerant and is to high pressure?

[Mark94]

And yes, no high speed relay fan. Where did that go!?!

Maybe in last models it doesn't exist. Practically two fans with lower speed it is most often enough...

Maybe you have to much refrigerant and is to high pressure?

Possible, but it was last regassed 18mths ago and has been fine. AC does work when turned on too..... It was mentioned the switch has two parts, one normally open and one normally closed. So if the switch was working on one part of that (to make clutch work and AC work as expected) but broke the other....?

All guesswork for now.

[wojciech]

And fans are only on when engine running. Not when ignition only is on.

Are you sure, that AC compressor doesn't work? Did you visually check compressor clutch - and inside wheel doesn't work, only outside belt wheel works?
I suspect - maybe clutch is permanently connected and when engine is running - compressor is still working too...

[Mark94]

AC clutch 100% working OK. AC compressor works as expected. AC works fine.

When everything connected an AC is "on" - the clutch makes its noise and the wheel to compressor starts spinning, and stops when clutch is out.

From previous posts, the high pressure switch has 2 switches, I think one controls the ECU feed for the AC/compressor, the other controls the fan-on request. Only one partrt of the switch (or cabling) has failed.

Once I get a new switch I will analyse the connections and post back.

[Altransit]

I don't know if this is any help to you,



Engine fuse box from 2004 Mk6 with aircon:-

[v8dave]

From previous posts, the high pressure switch has 2 switches, I think one controls the ECU feed for the AC/compressor, the other controls the fan-on request. Only one partrt of the switch (or cabling) has failed.

Sorry if I did not make this clear enough in the other thread.

Neither contact pair is connected to the fans wiring directly. Both are connected to the ecu.

[Mark94]

No you were perfectly clear to me. I think the HP switch has partly failed and the part that tells the ECU to put the fan on is broken
I will replace switch and report back as it appears as if this fault is rare with a weird side effect
Thanks for your input and ideas
Always harder to communicate on a forum!

[Mark94]

**** SOLVED ****

Well, firstly thank you to the helpers on this forum.

I bought a new A/C high pressure switch from Ford (for me, 7S43-19D594-AA ), and plugged it in, and hey presto fans didn't run but A/C compressor did work okay (only for a few seconds as the sensor wasn't plugged in).

Removed old sensor (14mm spanner) and the pipework did auto-seal Pretty tight behind the intercooler but only needed a small turn and came off by hand. Got new o-ring (weird size but local parts place had one - guess at r4.5? ), soaked in £8 of refrigerant oil (got loads spare!) - and connected all up, and hey presto all works fine - A/C works and fans are working as expected. And no gas/fluid leaking around new sensor.

Now, weirdly, the old switch and the new switch have the same continuity across pins when off the van, so I can only assume the old switch was (partly) overly sensitive to a bit of pressure in the pipework which was forcing a connection to the fan-on switch which I assume is shorting an ECU pin to earth (as removing A/C fuses didn't remove issue).

Seems a rare issue, for sure I've seen no exact fault documented elsewhere.

So - if anyone finds this thread with similar issue, see viewtopic.php?f=5&t=163332 and see viewtopic.php?f=5&t=163392 as well, and the quick test is unplug the high pressure switch. If fans stop, try replacing that switch.


So genuine thanks to the help given!


(Sorry for posting same end-message on both threads, just to ensure future searches give same answer)

[ossie cossie]

Very interesting thread.