Request for help: diagnose electrical problem

Apr 25th, 2003, 03:20 PM

Hi y'all:

I am asking for your help in diagnosing an electrical problem on my 1994 Nissan 4x2 P.U. truck, with the basic 4-banger KA24E engine.

The problem I encountered is that all of a sudden my tail lights AND the lights on my instrument panel no longer work.

I have checked to see if I had a burned-out fuse, but all fuses under the dash are OK. There are two relays mounted close to the fusebox, and I tried switching them around. Did no good. I have also switched around the relays mounted near the passenger-side wheel well, without any result. Those things don't appear to be accessible, without destroying them, so I can't really check the condition of the relays...

I suspect it may have something to do with a fuseable link going on the blink (hey, that rhymes!) ;-). Unfortunately, I have no idea about how to test those things, or even what they look like (all I know is that they are supposed to be located close to the positive battery terminal).

I am looking forward to any help you may be able to give me.

Thanks!

Bob Boester

aaronford · Apr 25th, 2003, 09:20 PM

Did you replace the stereo recently? That's normally the culprit. A miswired inst wire during a radio rewire will cause this. BUT it should pop the fuse. If you have a test light (12v), try touching both metal contacts on the back of the fuse (exposed). You should see power on both sides of the fuse. This will help identify a burnt fuse that may look okay to the eye. Make sure there isn't a trailer harness adapter installed that may be malfuntioning. Before you get into any of this, make sure the bulbs are good or you wind up like me, shooting a brakelight problem for hours only to find that all four bulbs were blown. Aaron

1997XETruck · Apr 27th, 2003, 01:30 AM

Is it possible that the dimmer switch for the dash or the headlamp switch has a problem? I'd suspect a fuse you haven't found yet - a good multimeter will be your best friend in finding something like this...

Heath

Warren · Apr 27th, 2003, 12:06 PM

Bob, is it just your tail lights and instrument lamps? Or is it your brake, turn, backup, side marker, etc? The only thing I see that instrument lamps and tail lights have in common is ground. But looking at the wiring diagram, if your ground is faulty, none of the lamps on the back of your truck should work. How about your front end lamps, are they working? turn signals? A complete list of what is and isn't working would help tremendously in paper-shooting this thing. Warren

Apr 27th, 2003, 10:24 PM

Hi Aaron, Heath, Warren:

Being a newbie in this forum, I can be expected to do things the hard way, in the beginning, correct?

I just now sent each of you an individual e-mail reply, instead of just posting a reply with a response covering my response to all of your suggestions.

To keep this thread going, I'll try to summarize what I wrote each of you.

I double-checked the lights that were and were not working:
Working lights: Head, brake, backup, dome light in cab. The radio and wipers are also working.
Non-working lights: tail, license plate, instrument panel lights, running lights (next to head lights).

It occurred to me that all of those non-working lights are controlled by the head light and turn signal switch in the stalk on the LH side of the steering column. The middle position of that switch should turn all of these lights on, and they should all stay on if the switch is moved to the headlights-on position. Question: could this switch be the culprit? (I believe one of you indicated one of the switches might be at fault...)

Now, if I only knew how to use my multi-tester to check that switch out, I might be home free...

Any step-by-step instruction on how to use my VOM to test this switch would be greatly appreciated.

Anyway, I will be looking forward to any additional suggestions (or instruction) you can give me, so I can get this otherwise great buggy of mine going again (at night).

thanks for your help in helping me noodle this thing out!

Bob

aaronford · Apr 28th, 2003, 05:22 AM

I'm not sure about exactly which wires on the switch are involved in this, but this still sounds fairly simple. It sounds like you have a open or short in the inst/running light circuit. All the items you describe are in the same circuit. IE the running lights. First, make sure you have isolated the fuse and it checks good across the ohm meter. Make sure there is power to the feed side of the fuse and check to make sure the volts are making it through the fuse. If there is power to the back side of the fuse, next isolate the wire from the fuse to the switch by running a continuity check between the back side (fed) side of the fuse and various poles on the switch. Do this with the fuse removed so you are not powering anything else. When you find it mark it. Now isolate the switch to light wire by running a cont check between the power side of the bulb and the switch. Mark this as well. Now test the switch by running another cont check between the poles of the switch and turning it on. It should read 0 in off and infinite in on. Somewhere in this you should find your problem. You can feel confident that the problem is on the power side duee to all the lights having seperate grounds. The only thing they have in common is the feed side. If there is no power to the feed side of the fuse, check the connector on top of the battery terminal, as i think this is where this circuit is powered from.

Warren · Apr 29th, 2003, 02:22 PM

Just a note here. When testing continuity, the off position should read infinite, and 0 in the on position.

aaronford · Apr 29th, 2003, 02:56 PM

Thanks... Aaron