Can ammeter cause trouble?

marty in Ohio

marty in Ohio

Well-known member
Friend has had a problem with his '30 coupe deciding to stop on it's own without warning. We've been through the fuel and electrical system and everything looks OK. I noticed that his ammeter was not registering and he told me it's never worked right. Can a bad ammeter affect the way a car runs or is it just a gauge?
 
All power on the car, except for the starter, passes through the ammeter – in one side and out the other. This includes flow to the lights, distributor, and charging the battery. If the ammeter connections are bad, the car won't run.
 
There are two sources of power in a model A. The battery and the generator. What the amp meter indicates is the difference in flow between the load side (generator) and the battery side. Some of the reproduction amp meters are crap and some will work to a certain degree. The original Ford ammeters are by far the best.

I agree on connections. They should be checked periodically to insure they are clean and tight. Also, keep a spare condenser around at all times. They will die from heat injury at any time. The motor may run with a bad condenser but it won't run well.

Ford didn't protect their wiring very well. There are several places where folks can have shorts due to wire runs wearing against parts of the car that are directly grounded to the frame. These areas should have more insulated wire loom. A fuse kit on the starter is a must.
 
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Years ago, I had a VW Bug with an after-market ammeter I had the dealer install when I bought the car new. Sometime down the road I found the car hard to start sometimes. I also notice on cold damp mornings the inside of the ammeter glass would cover over with condensation. It progressively got worse. One morning I touched the ammeter glass, and it was hot.

I investigated and found the two nuts on the ammeter were not in the slightest tight and both leads were just swinging free on the posts. I suspect the mechanic that installed the ammeter forgot to tighten the nuts.

What was going on was two resistance contacts that generated heat and boiled the moisture off in the mornings.

An easy fix, tighten the nuts.

Tom Endy
 
Thanks for the posts. I guess we need to find a new ammeter. In checking I find that it's hard to find a good ammeter. Any suggestions?
Marty
 
First thing I would do is take the panel off and check the back of the ammeter. It might be an easy fix. You never know what kind of hack the guy before you tried. Make sure the wires are routed correctly, the nuts are tight, and the insulating spacers are in good condition. Check the terminals for resistance. You can remove it from the panel by bending up the bezel tabs (or sometimes the gauge just comes right off the bezel). Once it's off, you can test it by putting it inline with various currents, e.g., a horn that you have on the bench, or between a charger and a battery.
 
Paul Shinn recently released a new YouTube video on his channel about soldering the internal connections on new repro ammeters to make them safe (id - non fire hazard) to use.

An alternative is to find a good used ammeter - either an original, or an older reproduction unit with a brass case. New face plates and glass lenses are available, if needed.

Good luck - Jim
 
To aid quick diagnosis I'm a great believer in hotwiring to help eliminate and trace possible short circuits/open circuits. OK you may need a new ammeter but IMHO that's unlikely to be the cause of "...deciding to stop on it's own without warning.." as I asume that's a new problem and the .." ammeter was not registering and he told me it's never worked right..." is an old one. Diagram below. (in your case you might want to remove the yellow wire from the starter sw just to eliminate the ammeter and associated wiring completely )
 

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Can anyone here tell me why all the repo ammeters that are sold
are cheap and junky? Makes no sense to me at all. This is important.

Almost as bad as those caged rollers bearings being of not the greatest quality!
You can't keep listening to people that complain about the cost of parts .
 
I had my ammeter /wiring start smoking one afternoon.. Very disconcerting to see a fair amount of acrid grey smoke coming from the dash!

Turns out the ammeter nuts were heat damaged [over time] the wiring connectors as well.. and the ammeter studs themselves were loose inside the ammeter too. I am sure this condition was y e a r s in the making.

I since have cleaned the connections, replaced those affected wiring harnesses, the nuts too & secured the ammeter threaded studs. All seems well once more.

Oh, and I bought a reproduction ammeter just in case.. Well the ammeter nuts from it did NOT fit the original, and as stated above, it seemed poor quality overall.

My car has a LOT of time worn 'patina' which I rather like.. so the original will stay in place while functional....

M
 

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One problem on lot of ammeters I've opened up is the internal insulator on the shunt bar is generally just a fiber material a lot like paper but a bit thicker. The case insulators or the nuts are not a problem unless they get hot and melt a bit. This just makes the connections loose. The plastic coated nuts may have seemed to be a good idea but metal nuts with thin lock washers might be better. They likely used the plastic covered terminal nuts for better insulate the terminal ends against possible shorts on the inside of the panel.

Modern replacements just don't have the quality that the original meters had. The larger separate horse shoe magnet seems to make the indicator needle a lot more sensitive than the current types that have the tiny magnet on the armature.

The one I have on my 1956 850 Ford tractor is a cheapy too but it will tell me that it's charging at least. Finding good quality small indicator devices like this is almost impossible in the modern era.

Ford put those funky brass half wing nuts on the terminal box for a reason. A person can bypass the ammeter by putting an alligator clip type jumper wire between those two terminal box nuts. A person can also use them for other troubleshooting procedures.
 
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rotorwrench said:
Ford put those funky brass half wing nuts on the terminal box for a reason. A person can bypass the ammeter by putting an alligator clip type jumper wire between those two terminal box nuts. A person can also use them for other troubleshooting procedures.
Click to expand...

Will not adding a jumper wire to "junky brass half wing nuts" just add fuel to the fire if the ammeter or wires are shorted out?

I think I would pull the dash first to investigate the situation.
 
I agree that the new replacements are not good. Several years I bought one from Snyder's and the needle fell off the post before I ever got it in the car. I took it apart and put the needle back on and it fell off again. I called Snyder's and they refunded the money. I offered to send the "new" replacement back and they told me to just throw it away. They weren't worth the postage to send it back.
Marty
 
marty in Ohio said:
I agree that the new replacements are not good. Several years I bought one from Snyder's and the needle fell off the post before I ever got it in the car. I took it apart and put the needle back on and it fell off again. I called Snyder's and they refunded the money. I offered to send the "new" replacement back and they told me to just throw it away. They weren't worth the postage to send it back.
Marty
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That's funny, I had one of them do the exact same thing! Pure junk.
Mine was from Snyders as well.
 
Dino's A said:
That's funny, I had one of them do the exact same thing! Pure junk.
Mine was from Snyders as well.
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IMO, we are our own worst enemy when it comes to the vendors selling junk. Too many car owners are too tight assed to pay for quality so the vendors would be stuck with it but they can sell a cheaper (read trashy) item so that's what they stock. I have always believed that buying junk is more expensive than buying a decent item in the first place. For example, those ammeters that didn't even last long enough to be fitted into the dash were a TOTAL waste of money, that is zero value whereas, if a decent one were available and bought, the car owner would be getting value out of it for years. I'm not saying those guys are tight asses, just that there was probably no other option.
 
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