Themo Fan question

[Chubba]

Happy New year all.
Is the thermo fan on my '98;gu 4.5L petrol' over the a/c condenser only for the a/c or dose it have a duel purpose of cooling the main radiator as well? I suspect that it not working, under hot conditions with a/c on overtime at slow speeds in traffic the temp rises and a/c cuts out but with a/c off there is no problem with temp in same conditions. I have only just installed new radiator , a/c condenser and auto trans oil cooler. Any thoughts?

[the evil twin]

AFAIK the thermo fan should run when ever the A/C is running and also kick in if the engine temp rises past the set point of the temp sensor in the radiator whether the A/C is on or not.

That is certainly how the 4.2EFI's are wired

If you just installed a new rad it may pay to check that the correct sensor wiring etc has been used

[Dales300exc]

Mines a gq so possibly different, or faulty, I know, but fan only comes on when the vehicle gets hot. If ac is on on its own. Fan does not start.

[Chubba]

Thanks fellas, that's what I thought was the case .there is power to the fan from relay so either fan is fu or both the a/c sensor and the temp sensors are fu chances it is the fan if there is two sensors or dose it work off of one?

[the evil twin]

Thanks fellas, that's what I thought was the case .there is power to the fan from relay so either fan is fu or both the a/c sensor and the temp sensors are fu chances it is the fan if there is two sensors or dose it work off of one?

Nope... seperate sensors... and it should def run with the A/C thats the primary reason it is on there.

OK, seeing as I am a helpful bloke, page EC 424 of the nissan service manual for the series 1 GU's shows the Electrical Cooling Fan driven via a 30 amp fuse thru the Cooling Fan Relay (E8).

This relay (E8) is energised when and earth is supplied via
a) Pins 5 and 6 of the A/C relay (E5) when the A/C is on and that relay energised
OR
b) the Engine Coolant High Temp Sensor (E40) which is normally open and close pins 1 and 2 when the temp in teh rad (lower tank from memory) exceeds the set point of max 93 deg C.

When either condition is met then the relay will energise and supply 12 VDC to pins 1 and 3 of the Cooling Fan (E36) and pins 2 and 4 of the plug should be hard wired to earth.

That is def the setup on the GQ 4.2 EFI's as well altho the nomenclature and pin outs may change as I had to sort out mine a while back.

AFAIK it is also the setup of teh vast majority of A/C equipped vehicles Petty or Diesel

The cooling fan is hot of the battery but the A/C relay and Coolant Temp sensor are powered from the Ign On buss.

[Dales300exc]

Yup. Id agree. Fan should come on with a/c. I have just never been bothered to sort it out. Engine fan draws enough evidentally as my a/c is always cold. Will fix at the engine change.

[Chubba]

Excellent fellas. thankyou for the info will follow it up first thing in the morning . will let you know outcome

[NissanGQ4.2]

Thanks ET for your very informative info yet again.

Glad to see those that don't thank haven't put you off from helping out around here, its much appreciated

[the evil twin]

Thanks ET for your very informative info yet again.

Glad to see those that don't thank haven't put you off from helping out around here, its much appreciated

Hiya Cobber,

Takes a lot to stop me from shoving my nos... err... helping out

I must admit i don't hand out a lot of thanks myself usually cause I am gobbing off more than listening (I do so love the sound of my own keyboard)

What I do love to see is feedback on a thread (which chubba has kindly said he will provide) so that in days/months/years to come when someone searches they will find the full story.

[lucus30]

Yeah mine starts as soon as the AC is turned on. Though I am left wondering what the 2nd thermo fan to the right of the AC fan is for as I have never seen it come on yet. Any body else got a 2nd one on a TB45E?