My 72 240 tail light circuit overheats and blows fuses. everything works and I can't find any obvious shorts but it will run for about 15 minutes before popping the fuse. Once that happens the tail lights and the instrument panel lights go out but headlights are still on Anybody have any idea what might be causing it or how to best troubleshoot the problem. Any help would be much appreciated as this has me stumped

Thanks

clean ALL connections the resistance has increased because of the deposits how slight they seem . Clean the bulbs and sockets and all the plugs from the tail lights to the plug at the dash by the pasenger foot well . This should take care of it . Make sure the grounds are good also. Gary :rambo:

It doesn't sound like a classic short circuit to me, considering the circuit works fine, with all globes running, for around 15 minutes before the fuse actually blows.

What sized fuse do you have in the fusebox? If it's too small for the load that's put through it, it'll blow.

The external lights will draw nearly 2 amps of current in total, add around 1 to 2 more for the dash lights and that tells you what sort of current a normal tail light circuit draws.

If you're running a 5amp fuse, it'll be running pretty close to it's maximum whenever you've got the tail lights on. If you have a 10 amp fuse installed and it's blowing, there MIGHT be a problem.

Your external globes should be 5 watt, you might want to check them to make sure you don't have higher wattage globes (eg. 18 or 21 watt) installed. The higher wattage globes will draw more current, which could be blowing the fuse.

In Australia, the stoplights and taillights use a twin-filament globe behind a red lens. One filament's a 5watt and the other's an 18 or 21 watt. The turn signals are a separate, 18 watt globe behind an orange lens.

I'm not sure how the rear lights are run in the U.S. but you might want to check the globes and make sure they haven't been installed incorrectly, using the brighter, higher-wattage filament when you flip the taillight switch.

If you know someone else with a Z, compare their rear globes to yours and see if there are any differences.

One more thing, do you have anything else hooked in to the tail light/dashlight circuit, like a stereo? That MIGHT be tipping the fuse over the edge and making it blow too.

Here's a possible answer: http://www.geocities.com/zgarage2001/probs.html

It was what I experienced.

Look for "Fuses Keep Melting".

(Edited to clarify text to search for)

Is the fusebox heating up?

If the fusebox IS overheating, you might have some high-resistance connections in the fusebox itself. If that's the csae, the fuse would be melting due to high temperature, not blowing due to high current draw.

The headlights will still work as they're on a separate circuit.

Nacks, Gary, Steve

Thanks for the input. I checked it all out and found a couple of rusted sockets in the right tail light. I will be replacing them and see how it goes. The fusebox itself is not overheating and yeah the headlights are not affected. Can I get the sockets at any regular car parts store I don't see them in the Motorsport catalog