Possessed Ammeter

Many possibilities.

First, disconnect the battery and remove the steering wheel by removing the 6 Allen or Phillips screws. Remove the 4 knurled finger screws at each corner of the instrument panel, and gently withdraw the panel to expose the back of the instruments. Carefully examine the amp meter ring terminals on the large-gauge red wires. They may be loose which will result in your symptoms, and lead to fire. In either event, carefull snug these brass nuts (7mm I believe) to make sure they are tight. Loose amp meter wires leads to heat and potential for fire. (Do not over tighten and strip the brass nuts).

Second - if the wires were tight, go to the engine bay and inspect the fuses for "tightness" on the firewall. The 16 amp field current fuse could be loose in the connector, or the spade terminals could be loose. Tighten up the fuse holder by carefully pinching the holder cups together, and gently compress the spade terminals with a needle nose to make them tighter on the male spade of the fuse block.

Third - if this did not seem to be the culprit, then check the fuse blocks under the front bonnet for a loose fuse for the "regulator".

Finally, and the above were presented in order of likelihood and ease, you will have to dig into the alternator. You could have gummed-up brushes that are changing their conductivity with heat, or bouncing (bad brush springs) or dirty armature. A bad diode is rarely intermittent, but heat cycles could lead to intermittent diode issues. Working with the alternator is fun and easy, once it is on the bench. Removing the alternator from the car is one Royal Pain in the the Rosey Red Rectum. (I'm into alliteration). I refer you to other threads that have discussed this, but simply put, you will have to get under the car and very dirty.

I have not seen a regulator fail in this manner, but stranger things have happened. Perhaps it is a witch (do you live in Maryland?).

Jim S.

 

I have experienced similar problem and Jim's points are very valid having helped me solve the issues in the past.

also try the voltage regulator, it does funny things sometimes as well as the earth connection to it.

 

do a drop test on the battery as well. could be defective? If in a low state of charge it could cause these problems