Yet Another Ammeter Problem

[Jim W.]

I know there is a ton of stuff posted on Ammeter problems and I think I have read and tried most of the fixes in the posts, but still have the same problem.

I get no deflection from the Ammeter needle (67 small block) at all; ACC, headlight, headlight motors, starting, idling, driving, no movement at all. To test the Ammeter itself, I disconnected the plug and used jumpers and a AA battery. With just momentary touches, I get full deflection (right and left when reversing the leads). I assume this means the gauge is working. Testing voltage at the Ammeter plug, I had 12V on one side of the plug, but not the other, so cleaned the bulkhead (firewall) connector and now have 12.54 V at one side of the plug and 12.6 at the other when the car is not running. With the car started, I have about 14.6 V on the Horn Relay side of the connector and about 14.0 V at the Solenoid side. With the bulkhead connector unplugged and the Ammeter connector pluged into the Ammeter, I have continuity from the b & b/w pins on the bulkhead connector. I did the tests in the service manual (that I could) and the charging part of the systems seems to work, but there certainly was room for error on my testing abilities. I did take the cover off the Voltage Regulator and was surprised to see a lot of whiteish powder looking stuff all over it. It looks like moisture corrosion, but was fairly evenly distributed all throughout the VR. I cleaned the points on the field and VR relays just to be sure, but that made no difference either.
What should I do next? I am out of leads. Thank you,

Jim

[Jeffrey S.]

Re: Yet Another Ammeter Problem

Jim:
Did you check the plastic connector at the alternator? Had the same problem on my friends '66 and that was the problem. It had deteriorated, cracked and didn't make a good connection.
Jeff

[Jim W.]

Re: Yet Another Ammeter Problem

I have had in on and off a few times and it seems to be ok, but is will double check.

[Donald L.]

Re: Yet Another Ammeter Problem

There was an article in the Restorer a few years back that simulates your condition. Turns out the connections in back of the fuse box were corroded . Cleaning those connections restored the amp gauges function.

[William C.]

Re: Yet Another Ammeter Problem

Remember that the "ammeter" in a mid-year is actually a sensitive voltmeter. Check the small gauge ground at the starter as I remember that is one of the sensing points.

[Jack H.]

Re: Yet Another Ammeter Problem

The white powder on the inside of your voltage regulator is oxidation. That's pretty much a normal consequence of age + imperfect sealing of the VR cover to base rubber gasket. A small amount of oxidation won't cause problems and what you did (clean up as best as possible and re-seal the cover) should work.

Plus, there's evidence in your test data that the VR IS working... The fact that your probe measurements showed approximately 12 VDC without the engine running and closer to 14 VDC with the car started/running, says the VR IS sensing the need to turn the alternator on, IS turning the alternator on, and the alternator IS delivering charging current to pump the battery back up!

Now, you simply need to find the fault point(s) in the connections running to the ammeter. As mentioned, the gauge is NOT an ammeter (directly measuring current flow) but is a voltmeter monitoring the potential difference between two discrete points in the wiring and 'interpreting' the voltage differential as the equivalent current that must be flowing to generate this voltage difference....

[Jim W.]

Re: Yet Another Ammeter Problem

I hate reading threads that don't have the resolution and although this was a bit odd, I got it fixed, so that is what matters. Thanks for the replies. This was kind of a strange deal in that I went back and checked the resistance accross the ammeter and in both wires. All seemed fine. I plugged the connector back in, turned the key to ACC and saw deflection of the needle. Fired it up and the meter shows it charging like a dream. I suspect the problem was in the bulkhead connector all along and just didn't make a real good connection even after cleaning the pins. Thanks again.

Jim