Amp meter not working..

[Zedyone_kenobi]

My amp meter has been pegged off scale high since I bought the car, however, the fuel guage works fine, if not a little sticky. I have downloaded the factory service manual for the electrical portion, but all it says is ensure alternator is working properly...Which I am sure it is.. is there a simple test. I have a spare gage I can swap in, should I swap it out for my test, or is there something I can do before removing it.

[sblake01]

Is the gauge pegged all the time or just when it's running? You can use a multimeter to test the alternator. If it tests out okay, the gauge is bad.

Edited December 23, 2008 by sblake01

[Zedyone_kenobi]

Well, I assume the alternator is fine, as my battery has never needed a charge and it runs my lights and accessories just fine.

It stays pegged all the time, could a lose wire do the same thing, or are we talking fried gage. Could an aftermarket or different model year alternator do this.... I have no idea what the PO put on this thing.

[sblake01]

Shouldn't make any difference which alternator as long as it was wired properly the ammeter should work. The wiring to the gauge is a fairly simple plug in. It's likely the gauge that's at fault. I'd swap it out for the other one. Not too hard to do (speaking from experience changing gauges in a 280z).

[Zedyone_kenobi]

roger wilco...

I will let you know how it goes.

[JimmyZ]

You may have a 60 amp alternator in your Z. ???? Possible... Is it always pegged? (Even at an extra low idle?) The Z originally came with a 35 amp but some people have fitted later alts with the use of a special plug.

I've never had an amp guage go bad. Just know that the thick white wire with red stripe which runs in and out of the amp guage supplies your fuse block etc. It's an odd way of doing things but that's what the designer wanted. A simple volt guage such as found on later Z's would suffice.

My guage will indicate a charge for a while then it drops to neutral until a load is put on the system. It's kind of neat seeing the needle waver with tthe brake or turn signal lights coming on.

Think I heard of someone accidentally frying their guage hwen jumper cables were hooked up wrong.

2c

Jim

[sblake01]

The 76 280Z volt/fuel gauge has the same font as the 240Z amp/fuel gauge. I've seen that modification in quite a few cars.

[Zedyone_kenobi]

Okay, I did some preliminary amp guage investigating today to try to troubleshoot my problem. First, here is my current guage. It stays like this whether the car is on or off, load or no load. Its stuck here...

When I pulled my spare guage from the box... it looked like this, which is most likely more normal...

So I started to remove the glove box, as I hear its fairly reasonable to get to from there. But when I was cleaning out the glove box, I found a set of fuses, and I thought I should check out the fusebox to see if any had blown...

Picture with the cover on, notice where the Ammeter/Amp is called out...

Now look what I found when I removed the front cover...

One of these things is not like the others....one of these things is missing something.. can you guess what it is...

I concede that my guage is probably in need of replacement, but would it even work if this other part of the fuse box is not in place?

Should I be looking for another fuse box?

[JimmyZ]

Whoa! Thats WEIRD! You "shouldn't" have any tail lights.... But I'm sure that someone made a remote fuse somewhere down the line. Perhaps it's the fuse in the lower left corner or upper part of pic #2??? The side marker lamps corrode over time and can cause shorts which is why they may have switched to a separate fuse from the main block. This would keep you from melting the fuse holder.

Nice looking fuse box BTW.

[Walter Moore]

Whoa! Thats WEIRD! You "shouldn't" have any tail lights.... But I'm sure that someone made a remote fuse somewhere down the line. Perhaps it's the fuse in the lower left corner or upper part of pic #2??? The side marker lamps corrode over time and can cause shorts which is why they may have switched to a separate fuse from the main block. This would keep you from melting the fuse holder.

Nice looking fuse box BTW.

Oh, so that is why my fuse block looks more or less like the earlier picture, except that instead of the fuse clip being cleanly punched out like our friend's here, it MELTED its way out of the box without any outside assistance...

I doubt if the missing fuse is the cause of the current ammeter problem, but it may have contributed to it at some time in the past. It looks to me like the meter is just broken.