keep blowing the fuse for the dash lights/tail lights/park lights, Please help.

[oldfart76280z]

I blew the fuse that runs the dash lights, tail lights, side marker lights. After I turned the dash light dimmer switch, replaced the fuse. All was fine for a while, but then it happened again. Now as SOON as I replace the fuse it blows. What may be causing this? This is in a 1976 280z

Could it be the dimmer switch?

Edited February 6, 2014 by oldfart76280z

[djwarner]

I had a similar problem after some body work. It turned out the mechanic swapped the power and ground leads on a side marker lamp. It seems these are one of the few connections where this is possible. With dirt and grime, it is hard to tell which wire is power and which is ground.

Other than something like that, you are pretty much looking for cut insulation somewhere.

[SteveJ]

Other than something like that, you are pretty much looking for cut insulation somewhere.

Not necessarily. Sometimes there is corrosion in the light sockets themselves. If the corrosion bridges the gap between the positive and negative, it will act similar to a short.

Also look for splices in the wiring where you or a previous owner added something.

To get a better handle where the issue resides, use the FSM. Go to the BE section. You want pages BE-15 and BE-17.

1. Remove the fuse. It is the 20A fuse in the top right slot.

You will need a way to test for a short.

Method 1: Use an ohmmeter to measure from the right fuse clip to ground.

Method 2: Use a test light in place of the fuse. When the light is on, you have a short.

2. Turn on the lights to the running light position.

3. Use Method 1 or 2 to see if there is a short.

4. If so, disconnect connector C3.

5. Measure for a short. If there is no short, the problem is between connector C3 and the taillights or radio or heater control panel light or hazard switch illumination light or automatic transmission indicator light. (Note: if there is still a short, we haven't eliminated those circuits. We will confirm later.)

6. If there is still a short, disconnect connector C5.

7. Measure for a short. If there is no short, the problem is between connector C5 and the front marker lights/turn signals.

8. If there is still a short, it is between the switch and the dash lights.

9. If there is no short in step 8, reconnect C3 and retest to make sure you don't have two branches with short circuits.

Let us know what the results are with steps 3, 5, 7, and 9. Then I can give you more diagnostics.

[oldfart76280z]

I will go through each step once it warms up, thank you QUOTE=SteveJ;449716]Not necessarily. Sometimes there is corrosion in the light sockets themselves. If the corrosion bridges the gap between the positive and negative, it will act similar to a short.

Also look for splices in the wiring where you or a previous owner added something.

To get a better handle where the issue resides, use the FSM. Go to the BE section. You want pages BE-15 and BE-17.

1. Remove the fuse. It is the 20A fuse in the top right slot.

You will need a way to test for a short.

Method 1: Use an ohmmeter to measure from the right fuse clip to ground.

Method 2: Use a test light in place of the fuse. When the light is on, you have a short.

2. Turn on the lights to the running light position.

3. Use Method 1 or 2 to see if there is a short.

4. If so, disconnect connector C3.

5. Measure for a short. If there is no short, the problem is between connector C3 and the taillights or radio or heater control panel light or hazard switch illumination light or automatic transmission indicator light. (Note: if there is still a short, we haven't eliminated those circuits. We will confirm later.)

6. If there is still a short, disconnect connector C5.

7. Measure for a short. If there is no short, the problem is between connector C5 and the front marker lights/turn signals.

8. If there is still a short, it is between the switch and the dash lights.

9. If there is no short in step 8, reconnect C3 and retest to make sure you don't have two branches with short circuits.

Let us know what the results are with steps 3, 5, 7, and 9. Then I can give you more diagnostics.

[vtvette]

Hello Steve,

I am completing a rotisserie restoration on a '71 240z. All functioned fine before the car was disassembled. I just hooked the battery up for the first time today and Park/Tail fuse blows instantly.

I am having the same problem as the original poster - my 20amp Park/Tail fuse blows instantly when installed. The parking light switch is in the off position. If you don't mind a few questions:

1) You mention connectors C3 and C5. In all my literature pertaining to the wiring harness I cannot find any reference to "C" connector designations. Which connectors are these?

2) You reference sections BE-15 and BE-17 of the FSM. In the FSM I have page BE-15 pertains to diagnosing the Speedo, water temp and fuel gauge and page BE-17 refers to the wiper motor system? Should I be looking at these systems for a blown park/tail fuse?

3) This fuse should be hot at all times correct? IIRC the parking lights can be turned on with the engine off and key out.

I've removed the fuse and inserted a test light in it's place. I've gone around the vehicle and disconnected all parking/tail/plate/marker lights but the test light glows uninterrupted. Reading the wiring schematic it appears the park/tail fuse supplies power to the under hood inspection light as well as the combination switch on the column. I've disconnected both of these but the test light glows uninterrupted.

I will continue to study the FSM and perform tests. If you have any ideas to aid in my diagnostic I would greatly appreciate it.

Thanks!

Brian

[vtvette]

Update: I unplugged the 6 pin connector leading out of the fuse box and the test light still jumped in place of the fuse goes out. With the 6 pin connector disconnected I connected each pin from the male side of the 6 pin connector to it's corresponding pin on the female side of the connector. When I connected the green/blue wire the test light came on again. It appears I have a short in the green/blue wire. I'm off to lunch more diagnosis when I return.

[vtvette]

Final update - the under hood inspection light must be shorted internally. I unhooked it and presto - the light went out. I re-plated/rebuilt this light must have an internal short.

[SteveJ]

My guess is that it's shorted right where the power wire comes in.

[vtvette]

My guess is that it's shorted right where the power wire comes in.

I bet you're right Steve. I'll check this tomorrow.

The only other wiring issue I had was the parking lights would not come on. I traced the circuit to the parking light stalk switch which had power at the green/blue wire where the wire is soldered to the switch board. The green/white wire leading from the switch to the parking lights did not have power . I fiddled with the switch and presto! all lights working now. I'll either look into disassembling/cleaning the switch or, if that's not possible replace it. All other circuits in the car seem to be working 100%.

[SteveJ]

I have many switches on hand. I think Dave Irwin has some, too, and he repairs switches. If you want to look him up here, his user name is Zs-Ondabrain. http://www.classiczcars.com/forums/members/zs-ondabrain.html

[oldfart76280z]

Well I finally got tired of not being able to drive my z at night and solved my problem with blowing the fuse that run dash,tail and side marker lights.

The positive plug on the passenger rear side marker light was missing the plug insulation on the positive wire and was touching the metal. So I put heat shrink tube on it, put it back together and put in the fuse. Now all my lights

wwork again. Thanks for all the idea's on how to figure it out.

[oldfart76280z]

Thanks djwarner, I remembered changing the bulbs in all the side marker lights, before I started blowing the fuse. All is good now, finally.