VZ Thermo Fans N/W

[Timbo_hx55]

Hi all, fairly new to this forum thing so ere goes,

I have a 2006 VZ SS Crewman Thunder (6L), probably no different to any VZ SS as far as driveline go so I'm appealing to all VZ SS owners & those of significant wisdom..... Has anyone experienced problems with the thermo fans where one cuts in/out & the other doesn't (before thinking the obvious....read below)

Very recently I have noticed the engine running a touch hotter than usual (only about two needle widths higher but not overheating due to fairly cool weather) & when in traffic or stopped at lights have also noticed the air conditioning warming up slightly & seems like it can't quite maintain the set temperature, after a little investigation I've found the small thermo fan (passenger side) doesn't cut in at all, with the A/C off, the engine temp climbs, the large fan cuts in, cools the temp down & cuts out, with the A/C on the same happens.

I spoke to my brother (who also owns a VZ SS Crewman) & he checked his car saying both fans kick in after a short delay after turning on the A/C, which would explain my A/C warming up when stopped at lights or in traffic.

Yesterday, while replacing the radiator hoses, thermostat & t'stat hsg/neck as preventative maintenance, I removed the thermo fan assembly & connected it to 12 VDC to find both fans work as required on both the high & low circuits, as I understand it, the ECU reads the temperature from a sensor in the engine & thus controls the thermo fans accordingly, is there any known or common problems where the circuit controlling the fans is compromised or is it a possible ECU fault, my local dealership said "You'll have to bring it in so we can have a look"..........!!!!

Any help would be appeciated,

Regards,

Tim.

[VTClubSprtR8]

Going by what you have posted, have you checked the fuse for the small cooling fan, F107 (30A) in the engine bay fuse block?

[Timbo_hx55]

Going by what you have posted, have you checked the fuse for the small cooling fan, F107 (30A) in the engine bay fuse block?

Yes, I have checked the fuses, even tested them with a meter, I also forgot to mention that I swapped the relays for both fans yet the large fan is the only one cutting in/out.

Cheers.

[Waughy]

Had some trouble with my VZ blowing the fuse for the small fan, turned out the fan bearings were shot, drawing too much current. Replaced fan assembly and all good since. It was explained to me that the small fan should cut in under 40K/hr when the temp reaches a certain level (not sure off hand what it is). Sounds like the signal that would cause the fan to kick in is being lost somewhere. Maybe a dodgy sensor or loose/broken wire somewhere. I am unaware of any common faults with the circuit but. Apparently even the fans going bad like mine did isn't very common. Good luck sorting it. Might need to get it looked at by someone with a techII or similar to check for any codes that might hint at the fault.

[Timbo_hx55]

Ok, just a bit of an update, I replaced both relays for the fans, still the same, only the large fan kicks in/out, other than the fuse/relay block under the bonnet by the RHS strut tower is there any other fuse blocks in the car......reason I ask is the one under the bonnet doesn't have any accessory fuses for things like the 12V power outlet, radio/CD player or hazards/indicators etc etc, just wondering (although unlikely as both fan fuses are under the bonnet) if there is another fuse blown somewhere else, cheers.

[Waughy]

Yes, pull the panel under the driver side of the dash, the main fuse panel is under there, over to the right, you'll see it right away. Can't think of what fuse/s might be there that could be a cause, but it's definitely worth a look.

[Timbo_hx55]

Yes, pull the panel under the driver side of the dash, the main fuse panel is under there, over to the right, you'll see it right away. Can't think of what fuse/s might be there that could be a cause, but it's definitely worth a look.

Thanks Waughy, as you suspected there isn't any more fuses/relays under the dash for the fans, next step looks to be like you said & have someone with a diagnostic reader/tool to take a look for me, cheers.

[surfwagon]

Have you tried bypassing all the cars circuitry to see if the fan actually works.
Maybe like Waughy's yoursmall fan motor is shot or seized.

[Waughy]

Thanks Waughy, as you suspected there isn't any more fuses/relays under the dash for the fans, next step looks to be like you said & have someone with a diagnostic reader/tool to take a look for me, cheers.

No worries mate. You've covered everything I can think of, fuses, relays, even pulling the fan assembly out and putting power to the pins to see the fans do work. Only leaves wiring, a bad sensor, or a fault in the ECU possibly.

[Timbo_hx55]

Has anyone got a wiring schematic for an 06 VZ V8 that can give me the wire/pin numbers from the ECU to the fan relays, might be able to test the wiring myself before getting an overpriced bill from an auto electrician !!

[VTClubSprtR8]

Ok, just a bit of an update, I replaced both relays for the fans, still the same, only the large fan kicks in/out.

Have you checked the third fan relay? Relay R6 under the bonnet?

Is fan relay 2 a five terminal relay or a four terminal one? Have seen this done before.

These things could cause your problems also. Failing this it may be the ECU low speed/high speed driver circiut(s) that may have crapped out. I have the schematic for this model but no way of posting up pics. No upload account as yet, benn meaning to sign up for one but aint got around to it.

It was explained to me that the small fan should cut in under 40K/hr when the temp reaches a certain level (not sure off hand what it is).

Both fans operate regardless at either low speed or high speed on these models Waughy.

[JezzaB]

When you say your replaced the fan relays. Did you just swap them with some other ones in there (horn relay etc)? Or put new ones in? The GM relays are a different relay. Pin 30 and 86 I think it is are swapped compared to a standard relay. They must be a genuine Seimans or GM relay, not your run of the mill relay.ive seen normal ones put in and back feed the BCM and blow the low level triggers in it.

[Waughy]

Both fans operate regardless at either low speed or high speed on these models Waughy.

Thanks for that info, I was only going by what I had been told when I was fault finding my fans. PM sent re pics.

[Timbo_hx55]

Have you checked the third fan relay? Relay R6 under the bonnet?

Is fan relay 2 a five terminal relay or a four terminal one? Have seen this done before.

These things could cause your problems also. Failing this it may be the ECU low speed/high speed driver circiut(s) that may have crapped out. I have the schematic for this model but no way of posting up pics. No upload account as yet, benn meaning to sign up for one but aint got around to it.



Both fans operate regardless at either low speed or high speed on these models Waughy.

I can only see two relays in the engine bay fuse/relay box, one labelled engine cooling fan 1, the other labelled engine cooling fan 2.

I will have another look for a third relay, but I've spent a fair amount of time in there studying the label on the underside of the relay box cover, do you know off hand what this third relay is labelled ?? Cheers.

[Timbo_hx55]

When you say your replaced the fan relays. Did you just swap them with some other ones in there (horn relay etc)? Or put new ones in? The GM relays are a different relay. Pin 30 and 86 I think it is are swapped compared to a standard relay. They must be a genuine Seimans or GM relay, not your run of the mill relay.ive seen normal ones put in and back feed the BCM and blow the low level triggers in it.

Jezza, thanks for that & yes, I replaced the relays with genuine ones I bought from GM yesterday morning, one relay is a 4 pin, the other is a 5 pin, the relay closest to the engine (LHS) is the 5 pin one, but it made no difference, still only the large fan cuts in/out, at least I have some spare relays now.