Testing for a bad relay, jumper burned up

TOM SHELBY

MEMBER
2003 TOYOTA TUNDRA
205,000 MILES

I read the article here on testing to see if a relay is bad. Using that article I did what $600.00, three mechanics and multiple hours in waiting rooms could not. I figured out where the issue with my A/C was. (It was also a bad power wire)

in this case, I removed the relay and jumper-ed from one side to the other with no ground. Presto, after fixing the power wire the A/C kicked in for the first time since I bought the vehicle.

But, the jumper wire burned up. Got very hot and one end literally burned up.

If I put an expensive relay in there ($52.00 for a generic one at O'Reilly's, $92.00 for one from the dealer) will it burn up also?

If so, why?

1 Reply

STEVE W.

MECHANIC
13,572 POSTS

Welcome to 2CarPros. This sounds like the clutch isn't engaging, but a jumper doesn't really tell you where the problem is, that just shows that the clutch will engage when power is provided. It doesn't show if the AC controls can operate properly. The jumper burned up because of the current draw from the clutch on the compressor. They normally draw between 3 to 5 amps, however if it was partially shorted it can draw more and would easily burn a wire or relay.
From your description I would say you have a bad A/C clutch. That is likely the reason the power wire burned off as well. I would replace the clutch and relay. The short shouldn't have hurt the control side as the relay isolates them from each other.