TR6 Excessive reading on volt gauge

[Gliderman8]

I started to notice that my volt gauge is pegging full at 15+ volts. It will remain there for a min or two then return to the normal charging range of approx 14 volts. Engine rpm has no effect on gauge.
What’s going on?

 

[charleyf]

Normal.

 

[Gliderman8]

Normal.

I’ve never noticed a high reading like that before.

 

[poolboy]

I'd look into the condition of the battery or it's terminal connections...the alternator is trying to get the batttery fully charged and that's what the voltmeter is telling you.

 

[Gliderman8]

I'd look into the condition of the battery or it's terminal connections...the alternator is trying to get the batttery fully charged and that's what the voltmeter is telling you.

Thanks Ken. Will check the battery connections as well as the ground strap.

 

[poolboy]

You might want to have the battery 'load tested' Elliot.
The battery might show a full charge using a VOM but not hold that full charge overnight or less

 

[Gliderman8]

You might want to have the battery 'load tested' Elliot.
The battery might show a full charge using a VOM but not hold that full charge overnight or less

Thanks again. The battery (Deka) is relatively new; about two years old. I’m just returned from a 4-5 mile ride and the gauge stayed at 13.5v. Will do more investigating tomorrow.

 

[Gliderman8]

Did some checking:
Engine off= 12.8 v
Engine on= 14.1 v
Ground strap and battery terminal are good too. All seems perfect to me. Going to check the ground on the volt meter tomorrow then do a load test on battery.

 

[Sarastro]

Are you sure that the voltmeter isn't sticking ? Try tapping on it when it is high and see if that makes it return to normal.

I can imagine an intermittently bad regulator doing this, too.

 

[Gliderman8]

Are you sure that the voltmeter isn't sticking ? Try tapping on it when it is high and see if that makes it return to normal.

I can imagine an intermittently bad regulator doing this, too.

Tapping on the gauge was the first thing I did and it didn’t make a difference. Voltage regulator is on my list as well. When I ran the engine yesterday to check voltage the gauge stayed at 13.5v the entire time.

 

[DrEntropy]

My money's on the battery, Elliot. If the meter acted as it should after you've run the car a few days in a row, you may squeak another season out of the battery. OTOH, as Steve mentions, a wonky regulator could also be the culprit. Load test would rule out the battery.

 

[Gliderman8]

My money's on the battery, Elliot. If the meter acted as it should after you've run the car a few days in a row, you may squeak another season out of the battery. OTOH, as Steve mentions, a wonky regulator could also be the culprit. Load test would rule out the battery.

Going to get a load test today or tomorrow. Stand by…..

 

[Gliderman8]

Update.... took the car out to get the battery load tested at my favorite local alternator shop only this time I had my Fluke meter with me. About halfway to the alternator shop sure enough the volt gauge was pegged at 15+ so I stopped and put the meter on the battery..... Alternator was putting out 16.8 volts! I continued on to the shop and the volts dropped back to 14.1v.
The guy at the alternator shop (who owns a brit car) thinks there could be a slip ring going to ground intermittently causing the fluctuations in the output voltage. He thinks he has the same alternator on the shelf but without the connector for the volt gauge so he will just move mine over to the new one. As far as I know, the alternator in my car is the original and I have never had it rebuilt.
On the drive back home once again the volts spiked high so I just stopped and unplugged the alternator so I wouldn't cook the battery.
Going out shortly to remove the alternator.

 

[poolboy]

Did you bring along the schematic when you went to the shop, Elliot ?

 

[Gliderman8]

Did you bring along the schematic when you went to the shop, Elliot ?

No, why?

 

[poolboy]

I just thought it might help since you said something about moving the connection to the voltmeter

 

[Gliderman8]

I think what he was referring to was the single wire connection. Mine has a 3-wire plug plus a separate single wire connection.

 

[Gliderman8]

Update.....
My alternator was completely rebuilt and I got it back yesterday. This afternoon I installed it and took it for a brief ride. Volt gauge was steady at +14.2 volts for the entire time so it appears all is well!