Electrical Gremlins! Help!

sentrastud · Mar 28th, 2003, 11:03 PM

Alrighty,
On my way home tonight, the backlight for my dashboard panel went out so I was left with a nice black panel. Not cool. So when I got home i decided to see if it was just burned out a fuse. While I was there I decided to see if i could find the source of my rear defroster problems (it stopped working a month ago

). The fuses for it were ok so I decided to do a quick check of the other fuses. All were fine except for the rear lamps. (the taillights Brake lights still work fine though). Hmm, a ill just pop the spare 10A fuse in and test it out. Nope, no light from there, i yank the fuse out and its cooked... instantly.

When it comes to vehicle electrical systems i dont have a whole lot of knowledge so any insights would be greatly appreciated!
I figure the dashboard is just a burned out bulb, so ill replace that. But im baffled about the rear defrost and the rear lamps. Short? Bad ground?
One more thing, when i push the defrost button, it makes a click from somewhere in the dash and the defrost light comes on, but nothing happens to the window.

Also strangely my problem with the Handbrake lgiht staying on seems to have fixed itself? It works normally now even thoguh i havent done anythign to it.

Help!

-Nick

Crazy-Mart · Mar 29th, 2003, 12:23 AM

probably shorted !... try a light tester thingy into each side of the fuse holder and ground the other hand, it should light up on one way only than use a voltmeter , ground one side and get the other one into the slot the light didnt work you should get infinit resistance... if it beeps, its shorted !!... then the whole wire will have to be checked...

sentrastud · Mar 29th, 2003, 01:48 PM

quick update: i took apart the dash today to find the bulbs i need. All 3 of the dashboard backlights are cooked black...

rice rocket (soon) · Mar 30th, 2003, 01:02 PM

Possably check the wires on both sides of the rear window and see if the plugs are pluged in. also run your hand along the defrost strips to see if they are intact last week when i clean my car i found out why 4 of the bars were not working the strip had been scrached off, but you can go to Crappy Tire and buy a rear window defrost kit for like $10

SuperSentra4203 · Mar 31st, 2003, 12:31 PM

Quote:

Originally posted by sentrastud
Alrighty,
All were fine except for the rear lamps. (the taillights Brake lights still work fine though). Hmm, a ill just pop the spare 10A fuse in and test it out. Nope, no light from there, i yank the fuse out and its cooked... instantly.

One more thing, when i push the defrost button, it makes a click from somewhere in the dash and the defrost light comes on, but nothing happens to the window.

Also strangely my problem with the Handbrake lgiht staying on seems to have fixed itself? It works normally now even thoguh i havent done anythign to it.

Help!

-Nick

Well, my teacher said I need to do some electrical system troubleshooting today for my asssignment in class, so here goes,
If a fuse burns out instanty, make sure it's the right one, if not, you have a nasty short somewhere. That can be a pain in the ass to figure out.

As for the click, that is a relay for the button and light. we use that type of configuration in industrial motor controls called a memory/holding circuit. It is normal, just the relay firing.

Old defroster grids go out pretty easy, remeber, they can be ruined just by scratching the grid too hard. It won't work anyway since you are blowing fuses. Check the wires by the grid for shorts or bad insulation from constantly heating up throughout the years. If you think it may be bad, test it. Get a digital multimeter and test the grids two main wire for resistance. I'm not sure what the resistance is supposed to be, but it may be in the neighborhood of 1Kohms. Then check each induvidulal line from each side. Even if the main lines show the right amount of resistance, you can still have a few lines out and that gets annoying.

As for the handbrake light. Don't sweat it. I had the same problem. Me and my brother-in-law couldn't see anything wrong with it except the contacts were dirty. From time to time the contacts will stick and that light will show it's ugly face.

Hope that helps

-Rob-

Mar 31st, 2003, 12:50 PM

When you plug in a fuse and it blows it is called a short to ground meaning that after the fuse there is a short in the wire causing it to ground out making excess amps because of lower resistance causing the fuse to blow. A good way to check it is get a volt meter/test light and back probe the wire from the fuse back until you get no voltage reading I suggest using a volt meter for this.For your defogger chek the voltage at the center of each heat wire if it has 6 V then it is ok if its 12 V the wire is broken between postive end and center element and if it is 0 volts the wire is broke between center and ground. hope this helps!

sentrastud · Apr 2nd, 2003, 11:05 PM

Thanks for the replies everyone! Its fixed now.

Heres what happened:
way back in the day when i wired my deck i never bothed to connect the wire to the dimmer switch on my car (not need and it required some splicing in the deck harness to work anyway). So i simply took a piece of masking tape and taped this wire away. Over time the tape came loose and the wire was left to hang. Well it eventually came to rest across the contacts of another wire and shorted out. The wire is safely (zip tied) away now.

-Nick