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        General >> Problems >> Radiator Fans switchon threshold
        
(Message started by: TonyS on Apr 10^th, 2004, 12:48pm)

Title: Radiator Fans switchon threshold
Post by TonyS on Apr 10^th, 2004, 12:48pm

Trying to solve the problem of apparent overheating I monitored the PCM cooland temperature on a drive getting values between 65oC and 105oC with little apparent control over the coolant temp.

I bottled out at 105oC and switched the CC to HI which brought the temperature down. It seems the fans are not being switched on by the PCM, I've manually switched the main fan relay and this is working. At what temperature should the main fan be switched on?

Does anybody have a wiring diagram for this circuit so I can check the PCM command signal path and master relay?

I'm guessing the previous owner had an overheat problem so 'solved' it by removing the top thermastat - the engine is slow to warm up and the CC takes alot longer than my last Mk4 to engage after cold start.

Title: Re: Radiator Fans switchon threshold
Post by admin on Apr 10^th, 2004, 5:38pm

check out the scorpio wiring diagrams at http://www.carsoft.ru/avtorepair/sierra_el.html

pete c

Title: Re: Radiator Fans switchon threshold
Post by TonyS on Apr 10^th, 2004, 5:54pm

Thanks!

I wished I'd worked it back to the smaller (argh they are both the same!) of the fans probably being kaput.

But sadly not .. kaput PCM wiring harness in front of the radiator (easy) and to the side of the engine near the battery box (shot to b***ery :-[). With the state of the wires (manuf'ed date 03/96) its a new harness :'(. Picture to follow.

On the positive side (is there?) I found the reason for Bk2 pre cat H02S giving a heater malfunction DTC some time back - the water seal was obstructing the pins.

Also found the inlet tract was in pieces in front of the air filter, leading to hot engine compartment air being sucked in rather than cooler outside air. This helped to explain the higher than expected IAT reading.