motorola alternator troubles

[gone2ddogs]

I've put the alternator back on my A4 but I only have one connection to the ammeter. The regulator has three wires a green wire connected internally to the brushes a black wire attached to ground and a red wire that attaches to the diode bridge. With the engine running there is no output from the alt. If I connect a wire from the + side of the coil to the red wire from the regulator it starts charging and continues charging even if the wire is disconnected. If the wire is left on I cannot turn the engine off with the key because the output from the alternator supplies 12V to the coil. Am I missing a wire somewhere?

Thanks
John

[gone2ddogs]

I found the problem. The sense wire was broken off just inside the regulator case. A few minutes with a drill some dental picks, a magnifying glass and I was able to solder a pigtail wire to the lead. Heat shrink it, epoxy up the hole and it works great. I was unable to see the broken wire in the boat. I had to remove the regulator and look at it under a big magnifing lamp to fing the little nub that was left.

John

[Don Moyer]

John,

I'm not sure what model of alternator you have but it appears that you are not using the correct field exciting lead to get the alternator started. If the red lead is in fact the correct lead to excite the alternator, then you will need to install a small diode in that line so that the alternator cannot supply power to the coil which is currently (no pun intended) keeping your engine running.

Don

[coryh]

Diode

I have the same problem where my engine will not shut down with the key if the exciting wire is connected to the coil. Where do you buy and inline diode to prevent this problem?

[Don Moyer]

I'm thinking Radio Shack has a good supply of diodes. I'm not sure how they're rated, but if you tell the clerk what you're using it for, perhaps they can help you select the correct size.

Don