Elec Fan issue on Grand

[pondy653]

Hi guys maybe you can help
I'm a green oval man but my mate has a Grand on a 99 which seems to me to be over cooled.
By this I mean the Elec fan cuts in at around 90-92 ish degs even when driving. He noticed that his lights were dimming for approx 1/4-1/2 a second whilst driving at night.  He has been advised by our local Jeep main Steeler that his Alt is breaking down however I have just had the motor running on my drive with all elects on (heated seats, rear window etc) and the alt continued to produce 13.2v even with that load only dipping to 13v for around 1/4 to 1/2 a second when, you've guessed it, the fan cut in.
So now I have completed this rambling story what I'm asking is;
1 what temp should the elct fan run at?
2 is it normal for a grand to have dimming headlights when driving?
3 where the F*"% is the fan switch on the engine?


By the way it had a new exide battery fitted 2 days ago, this has not fixed the prob.


Many thanks in advance


Tony C

[Bishops Finger]

Err Im no tekkie but....

In answer to2 .....No




Hope that helps a bit

[Cherry Bomb]

The lights on my XJ dim very briefly when the fan cuts in, not sure why but it doesn't seem to cause any problems.  The headlight wiring on US trucks is a bit on the crap side, so that could have something to do with it.

The electric fan should only cut in when the temp reaches about 105+, but it does cut in and out constantly when the air con is on, so chaeck that first.

[skip]

in answer to no3. there won't be a fan switch on the engine as it's controlled by the ECU, could be a duff temp coolant temp sensor.

[AdrianW]

I've got an XJ so it may be different on the ZJ/ZG. The electric fan will kick in when the engine is extremely hot but also kicks in to cool the aircon condenser if the heater controls are on any aircon setting - blue zone or windscreen. The fan can cycle on and off at short intervals. On the XJ the Powertrain Control Module (PCM) is responsible for controlling the fan and output voltage from the alternator (as well as other 'stuff'). Dip in headlight performance is probably just where PCM increases output from the alternator to allow for the fan cutting in.

Extract from WSM below re High Pressure Switch on 4.0 XJ

The Dual Function High Pressure Switch controls both A/C clutch engagement/disengagement, and electric cooling fan operations. The switch is located on the discharge line near the compressor. The switch is screwed onto a fitting that contains a Schrader-type valve, which allows the switch to be serviced without discharging the refrigerant system. The discharge line fitting is equipped with an O-ring to seal the switch connection

Alternatively, I could be talking bo!!ocks  :lol:

HTH

Adrian