Ammeter reading backwards

smurph

smurph

Senior Member
I've been on the forum recently with a string of woes trying to track down a short . I think I've done that now (seems to be in the pop out switch or armored cable). However after replacing and rewiring the behind the dash wires, the ammeter is reading a charge when it should be showing a discharge. Easy answer-- switch the wires on the back of the ammeter. Done. And still showing a charge instead of a discharge even after switching wires! What gives ? What could cause this to happen?
Still out at sea when it comes to electricity, but I think I'm learning a little!

Thanks in advance fir your help.
Smurph
 
are you sure it is supposed to be showing a discharge?

what does it show with all the wires removed?

Do you have access to a known good ammeter someone would be willing to let you try? With a pledge to replace it if you smoke it?
 
I'm sure it should be showing a discharge-- have tested with brakes , horn and lights. I have had the wires switched to both sides of the ammeter and it only reads to the charge side when it should be showing discharge! No other wires changed . Makes no sense to me-- what gives?
Smurph
 
Yep, something isn't making sense here.
If you didn't change the battery ground polarity, and the engine is OFF, and you changed the two wires on the rear of the SAME ammeter, then the needle would have to read the other direction.

I assume you didn't take the meter apart and change the ring magnet by flipping it over.
 
1930 coupe said:
Double check to make sure you did not get confused and put the wires back on the same posts that they came off from. I have been an electronic technician for 45 years and that is the only thing I can think of that would cause the meter not to reverse.
Click to expand...

Tom Wesenberg said:
Yep, something isn't making sense here.
If you didn't change the battery ground polarity, and the engine is OFF, and you changed the two wires on the rear of the SAME ammeter, then the needle would have to read the other direction.

I assume you didn't take the meter apart and change the ring magnet by flipping it over.
Click to expand...

I agree, it can't work the same way with the wires in one way and again reversed. I mean you are only swaping two wires right
?
 
heres a thought,if you are running an alternator and had a wiring problem is it possible you damaged the alternator?
 
All good info, you're getting it from the best. Have you been reversing the battery ? What charging system are you using ?
As said, if nothing changes except ammeter wires, the meter has to read the other direction. Step on the brake, which way does it read ?
 
I recently (two years ago) bought a 1928 040-A Roadster. When I bought the car the older gentleman had said he hadn't driven it in a couple of years. During our conversation he stated that his son had come out and worked a bit on the car. Anyway the car seemed to drive fine on my test drive, the price was righ and we swung the deal. All seemed fine for a coupe of days as I just drove the car. All of a sudden the battery just died. I have to admit I was not paying much attention to the ammeter. Anyway I decided the battery was just old and I was more than happy to put in a new one. As always when I take anything apart I took a picture of it first (what did we do before digital photography!?) I saw that the battery was hooked up using a "negative" ground. Had the system been switched over??? I thought this might a possibility and the car had seemed to run OK so I hooked it up as it had been. As soon as I got back in the car I noticed the ammeter would react in exactly the way smurph describes. It would go negative when ever I revved the engine. I immediately switched the battery back to positive ground and all was fine.
 
Same thing happened to a friend that bought a '36 GMC pickup. Engine ran like crap, battery would go dead, truck would die after just a few miles. Finally figured out the battery was connected bass-ackwards.

PeteCruz2715 said:
I recently (two years ago) bought a 1928 040-A Roadster. When I bought the car the older gentleman had said he hadn't driven it in a couple of years. During our conversation he stated that his son had come out and worked a bit on the car. Anyway the car seemed to drive fine on my test drive, the price was righ and we swung the deal. All seemed fine for a coupe of days as I just drove the car. All of a sudden the battery just died. I have to admit I was not paying much attention to the ammeter. Anyway I decided the battery was just old and I was more than happy to put in a new one. As always when I take anything apart I took a picture of it first (what did we do before digital photography!?) I saw that the battery was hooked up using a "negative" ground. Had the system been switched over??? I thought this might a possibility and the car had seemed to run OK so I hooked it up as it had been. As soon as I got back in the car I noticed the ammeter would react in exactly the way smurph describes. It would go negative when ever I revved the engine. I immediately switched the battery back to positive ground and all was fine.
Click to expand...
 
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