Quote:
Originally Posted by castrol
Okay here's where I am...
I swapped wires. Started coach. Still no tach and still not showing volts on gauge. Measurement on isolator shows same.
Until I jumper it. And I just jumpered the posts momentarily. I heard the alternator kick in and I took the jumper off to get my dvom. When I walked up front the tach is working. Alt Fail light is off. The gauge shows charging. I've got charging at the batteries and the isolator.
But, if I turn it off and start it again, it goes back to the previous setting. Unless I jumper it briefly and then everything goes back to full working mode.
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I'm relying on a fuzzy, aged memory, but I had problems with a 93 Dynasty which had its alternator replaced with an "equivalent" one. There were TWO problems, that resulted from the fact that the two alternators had a different number of wires connected to them.
1) The alternator required a voltage sensing wire connected DIRECTLY to the battery post, and NOT to any other "equivalent" location. The voltage sensing wire is measuring tenths of a volt, and locating it, for instance, on the HEAVY battery lead where it connects to the starter would not work well. It caused the voltage output to pulse at about once/second.
2) The older alternator required an external "excitation" wire, and the new one did not. That left the installer with one "extra" wire, and I cannot remember where he put it, but it caused a problem. The type that requires an "excitation" wire, will not work without it.
I think if you understand even a little about how alternators work, you may be able to compare the two wiring diagrams and possibly determine what is wrong. In all the descriptions of problems like this that resulted from replacing one alternator with a "not quite equivalent" one, the problems were always mis-wiring. Sorry I can't be much more help.