vt cooling fan

[Cheap6]

Yep, both windings in both of the motors (on the early VT) are required for high speed fan operation. The normally closed switch contacts in the 5 pin relay ensures that both high and low speed (= 4; 2 x 2) windings are switched on by the high speed relay even if the low speed relay doesn't work.

A consequence of this is that when testing the fans' high speed operation the 5 pin relay has to be in place or at least the normally closed terminals jumpered together.

Either of the windings in the fan motors can fail independently of the other.

You might try checking the resistances of the fan motor windings also.

 

[Rhin0o8]

I Own a Series I VT Berlina.

As for the fans starting up when the A/C is put on, Mine starts the fans ALWAYS .... even first thing in the morning when Engine temp is well below 35 Degress

 

[tk55]

thanks rhino08, we had already established that fact but thanks for confirming it again

cheap6, i see that you know exactly how the fans work. so there are 2 seperate windings in the fan motor, one for low and one for high speed. thus 4 wires altogether. i tried to remove the fan connector so that i can measure the coil resistance but the connector seems hard to come off. is there a trick?

anyway i measured them plugged in. measuring from the 12v supply connector, the black wire to both motors are opened. the others has only about 1.5 ohm. what i don't understand is, when the 12v supplies are plugged in, i expect the black wire to show zero volt, but it has about 10v still!!! how does that work? does that mean the black wire is not completely opened but has very high resistance? i'll try measure that again with the multimeter at high reisistant range when i had a chance. it was freezing outside yesterday

btw i'm not so sure you need to short both fan motor windings for the high speed operation. when i short pin 87A of the low speed relay terminal to earth, the fans came on. when i short pin 87 of the high speed relay terminal with the low speed relay removed, the fans came on as well.

how expensive are the fans? i might just wire a bypass switch for the high speed and use it manually when in slow traffic

 

[Mayte123]

I don't think the fans are expensive, i remember walking past them at repco and they weren't too bad (can't remember the price) but if it helps, start your car with the computer in diagnostics mode (hold mode and "up" whilst starting the car) and switch to temperature mode (T) and you can see the actual temperature and see exactly when the thermostat opens up etc. Also might be handy if your going to install a manual switch instead of the relay (if so i would suggest also making it so that it switches with the aircon button).

 

[tk55]

thanks mayte123. the engine temp went up to 89deg before coming down. in an easy traffice condition it's running between 86-89deg which is very normal. cruising on the freeway it's pretty much stayed at 86 deg constant.

but in very slow traffic situation the cooling system become insufficient and started to go higher than 90deg. this is where it needs the assistance of the low speed fan. normally you can either put the aircon on so that it's on low speed constantly, or you wait till it gets to 104deg where the low speed supposed to comes on. but with the broken low speed windinds, the temp would keep rising until the high speed kicks in, apparently at 112deg!!! ouch, too hot for comfort......

if i were to do the bypass job, why did you suggest to make it switches with the aircon? i was only going to use it when in slow traffic. i use the aircon alot and i often make trips that takes longer than 1 hr. can the high speed fan handles that if it's on constantly for that long?

the only reason i can think of is if the aircon compressor needs the fan turn on for cooling, and it does not have a self-cooling fan built-in. would that be the reason?

i could easily re-wire the low speed relay control to the high speed relay so that when the low speed supposed to come on it turns on the high speed instead. what do you think of that?

 

[Cheap6]

btw i'm not so sure you need to short both fan motor windings for the high speed fan operation. when i short pin 87A of the low speed relay terminal to earth, the fans came on. when i short pin 87 of the high speed relay terminal with the low speed relay removed, the fans came on as well.

In the absence of the low speed fan relay (or jumper wire) only the high speed windings are being switched by the high speed fan relay.

The fans are on with the A/C because the A/C condenser pre-heats the air passing into the radiator, reducing it's efficiency. Also the engine load is higher at idle with A/C = more heat to be rejected into the cooling system.

Are you sure that you can't fix the fan operation rather than stuff around with the switch?

 

[tk55]

you're right cheap6, i totally forgotten that the aircon system has it's own radiator as well and that's the reason why it switches on the low speed fan.

i'll get the fans replaced. just thought i wire up the switch for now.

but i still don't understand what's wrong with switching only the high speed windings if they work anyway? is there a difference if the low speed windings are switched as well? do the fans go faster if both are switched as compare to only the high speed windings?

edit: cheap6, i've just finished reading this thread with your posts in it:

http://forums.justcommodores.com.au...26674-both-cooling-fans-not-running-help.html

my car is the same as "vt owner" which is a 98 vt berlina, the early type vt. so the cooling fans both turn on together but at 2 different rpm for low and high speed operations. hope this clear up some confusions.

 

[moose man]

tk55,
the only reason I can think that both your fans work occasionally, and that you have 10V at the black earth wire, is that there's an open circuit in your earth wiring from the fan relays to body. There should be near enough to 0V at the earth wire.
A couple of checks you can carry out before you spend money unnecessarily...

Connect the black earth wire from both relays (they are the same wire) to earth using a jumper wire, bypassing the body earth. Let the car idle to normal operating temp to test that the fans cycle.
104 degrees or so is fine. Even 108 will be ok, as long as there's liquid in the system. No engine damage will occur until there's insufficient liquid, and the metal engine component temperatures reach 130+ degrees. Alloy and steel engines survive even more than this regularly.

I reckon you have a fan relay earth problem.

 

[tk55]

hi moose man. thanks for the suggestion. i retraced my troubleshooting steps again today and i think i might not have done it quite right. the circuit diagram i have is quite confusing to start with. and i was having trouble removing some fuses and fan connectors didn't help. so what i said i'd observed may not be entirely correct. i'll have to do it again and come back with some more results. till then thanks again everyone.

 

[jen]

sounds like a prob im having with my vt at the moment except my radiator is stuffed was told had leaking hose when i got it home i had alot of water under my car looked under and have masive crack in the radiator tank thanks to the guy i got it of hes going to repair it for me cheap. i was told that if you put the low speed or high speed fan relay in the ignition realy and the car dont start that the relay is stuffed is this true? i was also told that the fans wont start until it gets to a certain temp and that the high speed fan is basicaly just for the ac. and aparently sometimes the fans themself are stuffed but theres a way you can test them or make them go. i have no idea about cars so any info would be appreciated.