Can anyone tell me why is my rear defogger's relay is clicking so bad when traveling down the highway? This only happened after I removed my hardtop and disconnected both connectors that connected to the rear defogger. /wwwthreads_images/icons/smile.gif Oh, it is in OFF position. If I was driving at low speed (below 35mph) it will never clicks.
Most defrost circuits have a "special" relay. The relay has a timing circuit built into them. When you press the defrost button the relay will engage for an amount of time specified by the manufacture. Usually it's enough time for the defrost circuits to engage, and melt the ice on the window. It's the same amount of time, every time, and is not adjustable. The only way you could adjust it is to replace capacitors or resistors that form the timing circuit within the relay. If you popped the top off the relay you'll easily see these components.
So now you take off the hard top and the relay starts clicking... and clicking and clicking without anyone pressing the engage button. This points to one of three possible problems that I can think of:
1. The relay is built so that it needs the load of the defrost circuit. This doesn't make sense as the Hard Top is meant to come off.
2. There is some voltage getting to the engage circuit that's pulsing the relay and causing it to cycle on and off.
3. The relay is defective.
I'd rule out number 1, so that leaves 2 and three.
I'm betting on number three, the relay is defective, unless an owner has started rewiring under, in, or around the dash and rear wiring harness. If this were true, all bets are off, and it's likely number 2 that's the problem.
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