Very odd, I've had working A/C for over a week now and it just started doing this today. As soon as you push the A/C button the tach goes to zero and doesn't budge, turn the A/C off and it goes back to normal. Any ideas what this might be? Also, today was the first time I drove for more than a few miles with it on, and the engine temp went quite high, I assume this is normal, is it?

 

Well, how high did it go?

 

Initially it went up to around 1/2 way on the temp gauge, as I drove more, up a few small hills and stuff it went to 3/4 and seemed to stay there, but I can't be sure if it was gonna go higher since I had gotton to where I was going and turned it off. I didn't turn it on for the return trip cause it makes the car slow as **** and I wasn't in the mood for overheating.

 

The reason your tach drops so low is becasue with a 1.1L engine producing ~100HP, at idle it doesn't have much power to give to the air conditioner. I too have this problem and I've really noticed a definite change in performance when it is on i.e. it's difficult to shift well because the rpms will drop off so fast because of the pull of the air conditioner. I however don't know what the problem is with your colant temperature. My car usually sits right before the picture on the guage and never budges from there while I'm driving. Mabye flush the radiator?

 

no, the tach went to 0, no matter what speed you were actually going, as if the tach turned off somehow. But the odd part is that now it works again. I can tell this is going to be one of those intermittant problems that will never get solved. oh well. I would agree with the coolant flush idea, but I switched radiators, as well as oil coolers in january, so its pretty fresh. I have a black magic M150 e fan on it as well. It seems to be ok temp wise as long as I don't go up hills or anything, I guess its fine. and yes, the car is slow as **** with teh air on, damn, I knew it robbed power, but this is crazy.

 

damn thats pretty crazy..

i dont really turn mine on.. but im gonna try it tomororw morning if it does the same thing

 

If the tach drops to zero when u turn the a/c on that means that something is shorting out or cancelling out the electrical signal to the gauge. i would check all the wiring involved with the a/c (switch wires, etc) and make sure that none of it goes near any of the connections for the tachometer.