Both Cooling Fan's Not Running? Help

[nick713]

Hi, if anyone has idea's please help, VT '98 SERIES I. My Mrs. was driving our VT about 3 weeks ago and it overheated on her, due to a leak. Found out it needed the heater tap replaced. Stopped the leak, but the water was full on boiling! I have replaced the Radiator (B.New) and all the Hoses, still running verrrry hot. Temp. gage never goes above half way. But as I am bloody derrr at Car's, I noticed that the fan's are not kicking in at all. neither of them. Can someone please help me with this problem, All I can think of is the Relay(s) being replaced? Thanks heaps

[PRAVX II S]

Hey mate.
Try swapping the relays for the fan. find another relay the is identical to the fan relays in your fuse box.
The fan does not come on straight away it gets to a certain temperature then turns on and off to regulate the
engine temp.
If its not the relays the PCM sends a earth signal to the relay. On the PCM (F6) its a blue/white wire
that travels from the PCM to the relay coil. Get a test light or multi meter to test this earth signal.
Also you can turn on your air-con and the fan should turn on for the air-con side fan.

[VT Owner]

I have the same car and pretty much the same problem, After replacing the water pump, heater tap, radiator cap, flushing the engine & radiator then replacing the coolant with expensive stuff, the car still ran hot. After reading one of the overheated threads, I got the idea to check the fans and noticed that my low speed cooling fan wasn't coming on at all. High speed one activates at at the correct settings - 104c turns on and 99c turns off which is correct according to the manual.

The only thing I can think of is either my low speed fan is stuffed and I need a new one or the Low Speed Fan Relay is stuffed. Tried to get a replacement relay today but none of the local spare parts places stock it (it appears to be a Holden only one). Unfortunately being Sunday, Holden is shut and there are no other relays like it that I can swap to check.

If anyone has an idea on how I can check the fan is working by bypassing the relay, I'd appreciate it.

[Dayvo]

Unplug the electrical connection from the fan then run a couple of wires from the battery to the fan

[nick713]

Thanks heaps mate, I'll do those checks now

[VT Owner]

I didn't have to unplug mine - just waited for the high speed fan to come on and looked to see if the low speed was also running. It was so it means my problem must be the relay (I hope).

Nick, do you know if your high speed fan comes on at all? It should come on at 104c (which you can observe by pressing Mode and Up button while turning on the ignition).

[edals]

Have you bleed the system and changed the thermostat when you changed your water pump? Just can be common for over heating issues. Just a thought. not sure on ya fans though.

[VT Owner]

Yeah, I did bleed it and also put in a new thermostat.

It doesn't overheat anymore - it just runs hot (between 99c - 106c) all the time. The high speed fan is coming on way too often because it's doing all the work due to the lack of a low speed fan (I assume). As a temporary measure until I can source a new relay, if I knew which poles on the relay socket to jump, I'd jump them and have the low speed fan on all the time.

[banga]

try a lower temp thermostat than the one youve got

[VT Owner]

Got one, it's a 91c instead of the stock 95c. Makes no difference as the fans don't come on until 104c.

EDIT: It appears the Repco salesman lied to me - he gave me a stock one. According to the manual, a stock Series 1 thermostat begins to open between 89-93c and is fully open at less than 103c.

[Cheap6]

On at 104C, off at 99C is the low speed fan. High speed (+ low speed) is on at 112, off at 108C. V6.

The low speed fan is switched by the BCM, the high speed by the PCM.

To check the fan operation, remove the relays and connect a short length of jumper wire between the 87 and 30 terminal sockets for the relays. Do low speed first - the low speed fan should come on - put the low speed, 5-pin relay back, jumper across the high speed relay sockets and the high speed fan should come on.

To check the relays, if the first tests check out OK, put the relays back in but not all the way, so that you can access the relay pins. Connect each of the 86 pins to earth - body or battery terminal - the relays should click and the fans come on again.

To check the coolant temp. sensor and wiring, disconnect the temp. sender terminal, turn the ignition on and connect a 68 Ohm resistor across the temp. sensor connector. The fans should come on. If they do, the wiring is OK and check the sensor resistance - ~180 Ohms at 100C, which is close enough to operating temp..

[VT Owner]

On at 104C, off at 99C is the low speed fan. High speed (+ low speed) is on at 112, off at 108C. V6.

Damn, that's not what's in the manual VT-VY Service Repair Manual. On page 137 it states:

The high speed fan will turn on via the relay only if the low speed fan is on for 2 seconds and the conditions listed below are active:

- Engine coolant temperature is over 104c.
...

It then goes on to say that:

If both fans are on, the high speed fan will turn off when:
- Coolant temperature is less than 99c
...

In my car, both fans come on at 104c and both go off at 99c.

I'll do the tests you've detailed. Hopefully, something will appear broken and I can get that warm fuzzy feeling about the car back again.

[VT Owner]

Ok the results are as follows:

Jumped 87 to 30 on low speed relay - both fans come on
Jumped 87 to 30 on high speed relay - both fans come on

Jumped 86 to Earth on low speed relay - both fans come on
Jumped 86 to Earth on high speed relay - fan/s don't come on. Changed out relay for a known working one, same result, no fan/s comes on.

68 ohm test works. Display indicates overtemp at 135c. With ignition on, both fans come on in "high speed" mode. Turning the ignition off, both fans reduce RPM's to "low speed" mode.

Haven't yet checked the sensor resistance at 100c but I'll do that later today (I suspect it will be correct at approx 180 ohms).

Dumb question... I assumed from the manual that when they talk about the "low speed fan", they meant only one of the physical fans. It's not referring to the RPM state of both of the fans does it (ie. both come on but in a reduced RPM state, whereas "high speed fan" means both on but in an increased RPM state)?

BTW, thanks for taking the time to write up the tests Cheap6. Things like this help tremendously in identifying and solving problems.

[Cheap6]

I checked the temps. in some Holden factory service tech. data that I have for VT and VX. It tallies with what VN-VR run; they are on at 103C. V8 runs at lower temps. or the service manuals have been known to contain misprints .

Early VT V6 switch both fans on at "low" speed, then increase the rpm on both for "high" speed, late VT- switch only one fan on for "low" speed, and both for "high" speed.

You will have to have the ignition on to switch the high speed relay by earthing the 86 relay pin. That test will only work with power to the 85 pin. I missed that. The BCM is able to switch the low speed fan relay on with the ignition off so that relay has constant power to the 85 pin.

The low speed relay is a 5 pin relay. That can be swapped for a 4 pin sometimes.

I think, though, that what you have described - assuming that the high speed relay checks out OK with the ignition on - is consistent with normal early VT fan operation.

[VT Owner]

I'm thinking you're right - I must have an early model. Explains why the manual says one thing but the car does another.

I did pick up a valuable tip from the manual though - when I swapped out the top radiator hose for a new one, I cut the straight section out of the old radiator hose and used that to aid me in bleeding the system by shoving it into the mouth of the radiator and filling it up. Made the job so much easier. Air needs to be bled out of the system when the coolant is cold though or you run the risk of sucking more air back into the system.

Car seems to be running around the 87-89c mark now while driving and only creeps up to 104c when I stop at the lights or idling for a time.

In any case, thanks for your help.