When I switch to full blast the fan AND the a/c go off.

[jindy]

I have seen quite a few posts re VT fans not working at low speed, but my VT is the opposite. Low speed works fine, but when I switch to full blast the fan AND the a/c go off. Both fan and a/c work again when I switch to low speed.

Anyone else had this problem?

[axemurderer101]

fan speed resistor would be my first guess but im not sure if the high speed goes through the resistor so might be something else like the switch

[esca_ByDesign]

i know mine does that on my VY, i think it is a safety thing from holden, well at least mine is, when i go full fan and A/C it goes on for about a minute then turns off, then i wait 30 seconds and it comes back on for a minute and so on so on, its probly so the fan and a/c dont draw too much current or dont get too hot, thats my guess but someone can correct me if im wrong.

[Brett_jjj]

I know that with the VS models, the high ventilation fan goes through a relay to the blower motor,whereas the 1,2,and 3 speeds go through a resistor block and then to the blower motor..If the VT is the same setup,then check the ventilation fan relay. Im not sure if this relay is in the fuel box under the bonnet,or the fuse box under the steering column.

[jindy]

Yeah thanks for the advice all. I will get stuck in to it tomorrow especially looking for that relay.

[goose202]

According to the wiring diagram, the highest speed does go through it's own relay (on connector YB64 which is under the dash). If that is faulty then that explains the lack of high speed fan.

Other than the relay, since the other speeds work, it appears that the only fuse it could be is F13, but then rear demist would also not work.

It looks like there might be a feedback to the BCM via the resistor block, so I expect that if the fan is off (or the HS relay is faulty) the BCM automatically turns off the A/C compressor. I'm only familiar with the climate controlled models - I assume normally if you turn the fan to 0 it turns off the A/C?

[jindy]

Good one Goose -gonna check it this am. Thanks!

[jindy]

Bingo! It was the high speed fan relay under the dash - in the fuse box. Swapped it for the back window defrost relay in the fuse box behind the battery and she went gangbusters.

Thanks again.