Poor Amp Meter Reading

[DonWheeler]

I own GT40 II 2171. It has a Roush 427SR.
Recently I've noticed the Smiths amp meter reflecting the following:

1. Upon starting the engine, the amp meter reads approximately 25, then gradually decreases to about 5 over the next couple minutes. It basically remains a 4-5.
2. While driving, if I turn on the parking lights, the needle immediately goes to about 25, and remains there.
3. While driving, if I turn on the head lights, the needle immediately goes to about 50, and remains there.

4. I checked the battery voltage with the engine not running. It seemed fine, at approximately 13.45 volts.
5. I checked the battery voltage with the engine running. It read approximately 14.60 volts.

One other clue that may, or may not be associated with the problem is, that my water temperature gauge does not appear to work. The needle never moves from the initial setting.

Also, this amp meter difficultly may have been occurring for a long time, as I only have 1400 miles on the car; and I may not have noticed the amp gauge reading because I have rarely driven the car during the evening.

I would really appreciate it if some one could suggest a course of action to take to solve this problem, or identify what you think the problem is.

Thanks,
Don in Maine

 

[Jack Houpe]

Don, the amp meter in these cars are not a good reference to what is going on with the electrical system. I like many others have changed it out to a volt meter which will tell you what the battery potential is and if the alternator is keeping up with the electrical load. You could have a bad cell in the battery and never know it with just a amp meter. As for the Temp gauge that is pretty easy, it uses a pressure bulb filled with gas and is strictly mechanical. You will need to change it out or make sure the bulb in installed in the block water jacket.

 

[David Briggs]

The amp gauge in my SPF is not wired correctly, it only reads positive, showing only the alternator output.
There is a fix for it, I probably won't bother and will eventually go with a Volt Meter.
Dave

 

[Lynn Miner]

Don

There is a complete fix for this problem I posted in the How To section of the forum. The problem is well known and easy to fix. However, like many guys, I nixed the ammeter and replaced with a volt meter. There's a how on that too.

 

[Kirby Schrader]

As Lynn says below, some of the cars are wired such that the ammeter reflects the total system current as opposed to just that going to the battery. That's why, as you turn things on, the ammeter starts reading higher values.

My car was the same and I used the quick and dirty modification where you cut two wires and reverse them. It worked like a charm and everything works as it should now.

I kept the ammeter and added a voltmeter as well. I'm an old school, hick farm boy and like ammeters, personally... :laugh:

Check out Mr. Miner's 'how to do it article' and you'll be in business.

FWIW,
Kirby

I own GT40 II 2171. It has a Roush 427SR.
Recently I've noticed the Smiths amp meter reflecting the following:

1. Upon starting the engine, the amp meter reads approximately 25, then gradually decreases to about 5 over the next couple minutes. It basically remains a 4-5.
2. While driving, if I turn on the parking lights, the needle immediately goes to about 25, and remains there.
3. While driving, if I turn on the head lights, the needle immediately goes to about 50, and remains there.

4. I checked the battery voltage with the engine not running. It seemed fine, at approximately 13.45 volts.
5. I checked the battery voltage with the engine running. It read approximately 14.60 volts.

One other clue that may, or may not be associated with the problem is, that my water temperature gauge does not appear to work. The needle never moves from the initial setting.

Also, this amp meter difficultly may have been occurring for a long time, as I only have 1400 miles on the car; and I may not have noticed the amp gauge reading because I have rarely driven the car during the evening.

I would really appreciate it if some one could suggest a course of action to take to solve this problem, or identify what you think the problem is.

Thanks,
Don in Maine

 

[DonWheeler]

Thanks to all of you who responded to my inquiry.
I've contacted APT Instruments to acquire the volt meter.
I'll follow Lynn's instruction on how to install it.
The forum has been a very valuable exchange of information for me when I encounter an issue that I need help with.
Thanks,
Don in Maine

 

[Steve C]

I like the ammeter but didn't feel comfortable with the SPF 50A meter with internal shunt and fast on terminals.

Got a NOS original CAV (not CAV GT40 but CAV the meter mfg) on ebay that is rated 60A, has large external shunt and bolt terminals.

 

[Jack Houpe]

I like the ammeter but didn't feel comfortable with the SPF 50A meter with internal shunt and fast on terminals.

Absolutely great deduction, those spade terminals will end up frying someday and creating more problems than you can think of down the road.