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 :p

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) :smileyvault-cute-bi

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. :1062:

[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?

[the evil twin]

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?

2nd thermo's usually only come on with the high temp sensor.
Depends on who fits them and wires them up but that is the factory set up

Not much point in running both with the A/C when only one is needed but sometimes people take the easy way after factory and just splice a second one in.

[Yendor]

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?


Manual transmission TB45e have 2 electric cooling fans.

As said above the condenser fan should come on when the A/C is switched on.

The second fan should come on when the engine temperature goes above 100ºC

[Cuppa]

Manual transmission TB45e have 2 electric cooling fans.

As said above the condenser fan should come on when the A/C is switched on.

The second fan should come on when the engine temperature goes above 100ºC

Would the same apply to a TD42?

[Yendor]

Would the same apply to a TD42?

I'm not sure Cuppa. I thought the TD42 only had one electric cooling fan.

Does yours have 2?

[Cuppa]

I'm not sure Cuppa. I thought the TD42 only had one electric cooling fan.

Does yours have 2?

Oops! I was sure mine had two, but just went & checked, & sure enough, just the one, on the passenger side. There is an electrical connector hanging down on the driver side, same as for the passenger side fan though.
So with the single fan, would I expect it to come on with the air con, or only when engine temp gets above a certain threshold? Can’t say I’ve ever been aware of it coming on.

[Yendor]

Oops! I was sure mine had two, but just went & checked, & sure enough, just the one, on the passenger side. There is an electrical connector hanging down on the driver side, same as for the passenger side fan though.
So with the single fan, would I expect it to come on with the air con, or only when engine temp gets above a certain threshold? Can’t say I’ve ever been aware of it coming on.


It should come on when the A/C is on.

It should also come on if the A/C is off but the engine temperature goes above a certain temperature.

[the evil twin]

Oops! I was sure mine had two, but just went & checked, & sure enough, just the one, on the passenger side. There is an electrical connector hanging down on the driver side, same as for the passenger side fan though.
So with the single fan, would I expect it to come on with the air con, or only when engine temp gets above a certain threshold? Can’t say I’ve ever been aware of it coming on.

Yep, Rodney is right and should work the same as I posted earlier in the thread.

Not sure what the set point is on the TD42's but could be the same as the petty's @ max 93 deg.
If it is different it won't be much difference tho
Remembering also that is the lower radiator tank temp not the engine temp

[lucus30]

Manual transmission TB45e have 2 electric cooling fans.

As said above the condenser fan should come on when the A/C is switched on.

The second fan should come on when the engine temperature goes above 100ºC

Awesome thanks, service manual does not show a 2nd fan and had me wondering. Any easy way to test it works?

[Yendor]

Awesome thanks, service manual does not show a 2nd fan and had me wondering. Any easy way to test it works?

It's controlled by the engine computer so not really, apart from working the engine hard and getting the temperature up.

If you want to make sure the fan is working just disconnect the plug at the fan and supply direct power and earth to it.

[the evil twin]

It's controlled by the engine computer so not really, apart from working the engine hard and getting the temperature up.

If you want to make sure the fan is working just disconnect the plug at the fan and supply direct power and earth to it.

Hiya Rodney,

Agree with the testing...but... the wiring manual I looked up earlier doesn't show any interface with the engine computer. The power for the temp sensor and fan relay is direct from Ign On buss and the fan motor power is off the battery buss.

Thats AFAIK anyway... happy to be wrong (as usual) :tongue:

[Yendor]

Hiya Rodney,

Agree with the testing...but... the wiring manual I looked up earlier doesn't show any interface with the engine computer. The power for the temp sensor and fan relay is direct from Ign On buss and the fan motor power is off the battery buss.

Thats AFAIK anyway... happy to be wrong (as usual) :tongue:

Hey matey , Good to have you back.

What diagram was that? was it the one listed in post 5 ....EC 424 for the TD42?

Yeah the TD42 fan is not controlled by the ECU but the TB45e fan/s are.

This thread is starting to get confusing dealing with the different engines and transmission.

Cheers Rodney

[the evil twin]

Onya cobber, knew I shouldn't have been a doubter...

[lucus30]

It's controlled by the engine computer so not really, apart from working the engine hard and getting the temperature up.

If you want to make sure the fan is working just disconnect the plug at the fan and supply direct power and earth to it.

Thanks figured that will be the case will have to check it after a run on a really hot day if Melbourne ever has one again

[Chubba]

Just a note on my thermo fan problem. As you have seen all a bit confusing. Got too hard for me so I have buy passed all the shit and wired the fan through a relay direct to switch in cab so only I have total control over fan. Adelaide dew for some shocking heat this week,40+ so will be a good test.

[growler2058]

Hope you don't f@rk it up mate :)


PS the weather should be nice on the arvo shift ;)

[Chubba]

37 and I am home!

[growler2058]

37 and I am home!


But the mani has a/c

[Chubba]

Thermo fan no more, its now a on command fan and it works beautifully.

[mudski]

G'day Chubba. Late post just though I'd add to the discussion. I have just been through the exact same issue with my ZD30. I blew the top hose, Ni$$an want $840 for it, I got a new section made for it for $40 and then the regas. After then I had the same issues. I took it to my A/C guy, they plugged in their machine into the a/c lines to get a temp on the a/c refrigerant. Mine was sky rocketing and then the a/c would cut out. They said there is a threshold limit on the refrigerant temperature and once it reaches and goes beyond this point, the a/c will cut out. Thermo going flat out too. So they came to the conclusion the condensor temp was getting too high. So they let a little gas out to lower the temps so I could atleast use it. Which worked but they said the a/c won't get as cold as it should. They advised I should add another Thermo on the condensor as the OEM fans are useless and you might aswell wave a piece of folded paper over it instead. So I purchased off them a 9inch fan with a flow rate higher than a Davies Craig 12inch fan. Wasn't cheap at $110 though.
Got home and the first thing I did was remove the grill and old OEM fan, soaked the condensor in CT18 truck wash, and spray the goat out of it. Well! You should have seen the dirt all over my driveway just from the condensor. I was very surprised.
I knew from then on it would be way better even without the extra fan. But I put it on anyway and wired it in with the OEM fan.
The new 9inch fan when on pulls a crap load more air than the larger OEM fan does, which is what, around 13inch??? Now, on the last few 40plus degree days even sitting in traffic it works a treat. I have also noticed the needle on my engine coolant temp sits slightly lower too.
A PITA to fit but well worth it.
So a mental note to everyone. Remember to wash out the condenser every now and then.

Get this. When I was at the A/c guys workshop there was a 100Series Petrol there and they don't even run a thermo on the condenser at all!! And they owner of the Toymota wan't them to fix the issue of having shitty a/c but didn't want to pay to get thermo's added which would have solved his problem. Which was exactly the same as mine. Got to hot and the a/c would just cut out.
Was quite funny as the owner was there when I was and they show him my car to explain it and he was like "nup! Toyota made it like this so it doesn't need any fans!".

[Chubba]

Yeah, when I rewired fan I also changed over to a larger fan, heat this week in Adelaide has been brutal but the a/c has done its job and as you say Mudski, the temp needle if anything sits slightly lower. Very Happy.