99 au , fan one not getting power to the relay, if i bridge the out put terminal on the relay from the battery it works , where does the signal for it to turn on come from?

Hi,

There is a good write up in the Tech. Docs. I think the AU was much the same as my EL, with 2 fans and 3 relays. There are 2 control signals from the ECU, fans on and then another for high. In the low setting, the Fans are in series, and high they are in parallel. Sometimes the ECU needs to be reset, as it wont run them on high. Hope this helps.

One of the contact pins on fan 1 relay should have power and one of the coil wires should have power with the key on... The computer grounds the other side of the coil wire to engage the relay when the car is getting hot... That relay must also come on for high speed otherwise only one fan will work on high speed...

My AU the high speed only engages on a really hot day when the AC system builds too much pressure... It runs on low speed most days when stopped idling... And probably doesn't run at all when driving...

Cheers,
Tim