andy boardman

Evening

I have an 87 S4 euro which had fans that worked fine until I replaced the radiator the other day - now cooling fan 2 runs at high speed and 1 does not run - the fan speed will intermittantly drop away and the front flaps close, fan 2 tries to kick in and then everything defaults back to fan 1 (and the front flaps open) - this fan is running overspeed (very loud) now so I am worried that it will cook it.

With air con on the fan runs continuously as above - without / in traffic the fan will cut in and out but seems to do this rather too frequently - i.e. it does not cut in run for a length of time and then switch off - rather it cuts in runs then slows down / speeds up then maybe off then cuts in - almost regular cycles.

Any ideas? I have checked the feed to fan 1 and 2 and it seems to be OK when it thinks it should have two fans working. Does it seem like the finned module is kaput?

All help gratefully received as usual.

Andy

MikeN

Have you actually swapped the leads from one fan to the other to see if the problem moves? Check fuses 28 & 29 also, each fan has it's own fuse.

andy boardman

Mike - thanks for the response

I have swapped the leads and the feed problem seems to swap also - I have just been out again and checked the battery power leads and cleaned then as well as double checking the fuses - the relay XV111 cooling flap relay clicks in and out and seems to double ckick when the fan starts to slow down - i.e. it clicks and slows down and then almost like because the other fan has not kicked in the relay diverts full power to the original fan again.....??

Stumped.

Andy

MikeN

I wouldn't worry too much about what the flaps are doing.......your problem is the one fan not working. With what you have tried the next thing to look at would probably be the FOS (Final Output Stage).....aka, the finned module. If possible borrow a known working one and give it a try.

andy boardman

Mike - thanks

I'll give that a go - I've already asked around our specialists to see if I can get a 2nd hand one to try.

Regards..........Andy

aaron3

Andy,

There's a really good troubleshooting procedure in the manual that will pinpoint what component is the problem. If you need a copy, give me your e-mail.

Garth S

Andy,
You noted of the problem " which had fans that worked fine until I replaced the radiator the other day ".
The latter part caught my attention, as the last thing fixed is often responsible for the next problem.
Did you reconnect the wire harness correctly to the thermo switch in the lower left front of the rad end tank?

andy boardman

Evening guys - yes I believe so but I will have to retrace steps and check - there is definately no kick in of the second fan at all now whereas there was before - now one fan starts spins up to full speed holds then dies away before then speeding up again - no second fan at all.

I hope that I have a fan and a controller coming to swap over and see what happens. Others have suggested earth points need cleaning - I did those on the colis the other day but not the brown wire collection on the front lh( looking in the bonnet) corner.

I'll keep you posted - thanks for your help

Andy