Hi so you have some good answers so how are you going to cure it. i think you have no other option as most cars in the last 30 years are mostly computer all over the car it needs a specialist and where are you going to find such a guy. yes that's right a toyota dealer. or an auto electrician.
Has someone done work on the car for any reason? Sounds rather like miswiring!
The only electrical work that I know of is alarm related, which shouldn't have any effect on air con,,, but of course you never know...
It's worth pointing out that the fault isn't constant. I mean sometimes just the brake lights don't make the fan cut in, it will only cut in when something else is on.
It will even blow on / off, on / off with the indicators sometimes! And sometimes it works for a while with no extra load, or for a while after the extra load is removed, then cuts out randomly after a minute or two, so it's certainly an intermittent fault.
On turning on the air con, the fans (there are two in the rear of my Toyota Granvia) spin for a few seconds then stop.
If I turn on the headlights, or apply the brakes (making the brake lights come on) or out the car in reverse or even if I put the heater on (separate fan) then the fans cut in and blow cold air.
As soon as the "additional electrical load" is removed the fans stop again?
I'm thinking a bad earth or a defective relay but I'm no expert!
