Coolant Fan sensor in 87 4kq

[David]

Did you remember to bleed the system? There may be air trapped in there. There should be a nut on top of the raidiator. Loosen, start cold car, it will allow the air to be pushed out by the expanding coolant.

Dave
1987 CGT Special Build 2.3
SE Virginia

>
> From: "Cade Carvell" <ccarvell at nbsusa.com>
> Date: 2003/04/24 Thu PM 04:57:02 EDT
> To: <quattro at audifans.com>
> Subject: Coolant Fan sensor in 87 4kq
>
> Hello,
>   Long story short...I overfilled (I think) my coolant expansion tank
> last week...Which then caused the expasion tank to crack and the cap to
> go bad.
>   Today I replaced those parts and started the car again.  The temp kept
> rising and the fan didn't turn on.  So I did the checks:
>    1)  Fan works with a 12V battery feed just fine.
>    2)  Relay tests good. 12V causes it to Kick (Click)
>    3)  Checked the Lower radiator sensor measures .6 ohm resistace.
>
> Questions:
>    Since the lower sensor records .6 ohms, should I replace it.  The
> Bentley states 0 ohm resistance when open (Up to temp and fan should
> turn on).  I also noticed that if I go under car and short across the
> connector to wiring harness - Lower radiator sensor (0 ohm it) the fan
> still doesn't turn on with key off.
>    Did I miss something?  Is thier a fuse somewhere that controls this?
> Is thier another sensor?  I recently replaced the lower coolant neck
> sensor (Looked bad :-) ).  It worked after that (2 months ago)...DO I
> have a common wiring harness problem here?  If so, were would be the
> likely spot?  Any other tests I should run?
>
> Thanks to anybody with an idea or help, the poor Audi is grounded till I
> get this one narrowed down. :-(
>
> Thanks,
>
>
> Cade Carvell
> National Business Systems, Inc.
> 2919 West Service Road
> Eagan, MN 55121
> Office: 651-994-4400
>
>
>