I noticed to day that my defroster was cutting off before the 10 min limit that it use to do. I unplugged the wires from the defroster and tested the circuit grid by doing a continuity test and it was fine,showed no open open break. I then touched the fuse and it about burnt a blister on my finger. Now i know that this isn't right,any ideas as to what to check next?

 

I along with many others have or have had the same problem. The fix is simple. Replace the relay with a 30 amp fuse. I have had no problems since doing this. Do a search on defroster and you will find this fix repeated many times.

 

It's something to do with the resistance of the wires on the grid that draw too much current, then it overheats that little circuit breaker, and trips it. Not only does the defroster quit, but your power seat runs off the same circuit too, and it won't work either. I took mine in under warranty with this issue, and they replaced the back glass! But before they did that, they put in a new 30A circuit breaker, and the problem subsided for awhile. I think if you use a 30A fuse, it'll mask the problem, but technically there is a "problem" somewhere with you defrosters. As long as there's a fuse in place though, it should protect your car from melt-down.

 

Yeah. I seen the 30A fuse solution,but if something is wrong,then i want to find it,not make it go away.If the breaker gets that hot,then I am guessing that the fuse will get hot also?

 

Just noticed this thread.

The SAME THING happened to me several years ago: The rear defroster wouldn't work, and neither would the power seats. When I touched the 30A breaker, I burned my finger.

I brought it to the dealership, and after a lot of troubleshooting, it turns out I had an open short underneath the carpet on the console, between the front seats. The wires were touching bare metal.

I'm no electrical guru, so the fact that I had bought an extended warranty at the time of the purchase of the car...that helped.

Anyways, check underneath the carpet b/w the seats. That may be your culprit.

 

I'll check that.Thanks

 

I found the problem. The power wire that feeds a couple of things including the rear defroster had partially broke in half leaving a tiny amount of wire to pass the current. Replaced the bad section and it's working ok for now.

 

You could try this:

Connect an ammeter in place of the fuse/circuit breaker and turn on the defroster circuit. This measurement will be the total amperage to the defroster system. Then, hook up a 12 volt power source directly to the defroster grid, insert the ammeter in series with one of the wires and take another reading. This would bypass the entire circuit except the grid. I would guess the amp reading will be lower with the second test. The reason is that when a line in the grid is broken, (which is about the only thing I can see that can go wrong), the resistance will go up, because the lines are in parallel with each other. The more lines broken, the more total resistance in the grid. This would decrease the current draw which would be a less of a load on the breaker. Given that, maybe the problem is elsewhere such as what Red97LT1 described. Something else would have to be drawing the extra current even if the grid was bad.

 

I had this problem while my '96 was still under warranty (and I worked for a dealership). They replaced the switch twice, which obviously didnt fix it. I suspected the breaker, but they didnt agree... so I yanked it and put in a 20A fuse (I wanted to go smaller than the breaker for test purposes). That fuse didnt blow, even after 1 week of useage. So I replaced the breaker and it worked fine for a couple years. Now it's acting up again.

I think those little breakers just "wear down" and get finicky.