Fan constantly on, when the battery is connected now

[Tractor Dave]

This brilliant thread covers everything you need to know

https://forums.quattroworld.com/s4s6/msgs/21503.phtml

[Chris5044]

Hi! When you say connected battery, do you mean the car battery? If so, the problem may be related to the engine temperature sensor. The temp sensor may be reporting the wrong engine temperature to the engine controller, which will cause the fan to turn on all the time, even if the engine is cold. It is also possible that the problem is related to the fan relay, which may be stuck in the on state due to wear or damage. The cables between the relay and the switch can also cause a problem if they are damaged or not properly connected. If you suspect that water has gotten into the fuse box, this could be the cause of the problem. In that case you need to check the fuse box for damage and corrosion.

wow man, it can be all of these things..
Ive fitted a new 217 fan relay, and just fitted a 2nd hand 324 relay that was missing.
Coolant temp sensor is brand new and replaced the 2yr old one (which i think was working) - one at bottom of radiator right?

There is a suspected water going into fuse box. I have sealed it before with silicone sealant.. man this was such a **** design...

[Chris5044]

Could this be a fault with the F98 Thermal Switch?

[Chris5044]

This brilliant thread covers everything you need to know
https://forums.quattroworld.com/s4s6/msgs/21503.phtml

massive thankyou again!!! wow!!! great info!!

[Chris5044]

Magically guys, the s2 seems to have repaired itself. On the 2nd time connecting the battery, the fan no longer comes on immediately and the vehicle seems normal again. Perhaps the fitting of the relay has repaired this somehow? Taken it for 2 long trips and all seems good.

[newsh]

There is a suspected water going into fuse box. I have sealed it before with silicone sealant.. man this was such a **** design...

This is worrying me, what exactly do you seal up?Water can't get into the fuse box if the cover is on and closed properly, there's a rubber O ring in the lid. It's possible for water to get past the bonnet cable grommet though, this would drip down into the driver's footwell. A new grommet or some sealant can stop this. If water is allowed to pool in the scuttle it might seep under the fusebox and get into the car, it won't actuall get into the fuse box though.
It's really important that the drains from the scuttle area where the fusebox is mounted are kept clean and clear of dirt and leaves. The drains are oval holes at each end of the scuttle, draining out into the wings behind the arch liner. You have to remove the scuttle trim to see them and clean this area out properly.

HTH

John

[Chris5044]

This is worrying me, what exactly do you seal up?Water can't get into the fuse box if the cover is on and closed properly, there's a rubber O ring in the lid. It's possible for water to get past the bonnet cable grommet though, this would drip down into the driver's footwell. A new grommet or some sealant can stop this. If water is allowed to pool in the scuttle it might seep under the fusebox and get into the car, it won't actuall get into the fuse box though.
It's really important that the drains from the scuttle area where the fusebox is mounted are kept clean and clear of dirt and leaves. The drains are oval holes at each end of the scuttle, draining out into the wings behind the arch liner. You have to remove the scuttle trim to see them and clean this area out properly.

HTH

John

Hey thankyou for your reply. Ill double check, I think this is all clear. What I meant about water getting in. I silicone sealed around the box, as I read somewhere that water could get in, maybe I got it wrong. The sides of the fuse box, where it its bolted to the chassis. That rubber gets bad. Or can it not get in via this way?

[Tractor Dave]

They use a sticky butyl type sealant to bond the base of the fuse box to the chassis together with four bolts and it's normally good unless someone has removed it in the past.