Battery Isolator

[wa3vez]

1990 345 Motor Home. The isolator is a four terminal type which requires a voltage from the ignition on the fourth terminal. The Airstream manual shows a wire connected to the alternator output post with a diode in series. This diode shorted out and was blowing fuses in the ignition circuit. The wire is a #16 red. I removed the wire and everything seems to work OK. The book says it goes to a sensor?? Does anyone know where it goes and what is its purpose. Thanks.

[74Argosy24MH]

What alternator? Sounds like the sense wire for the regulator on a Delco.

John

[wa3vez]

Originally Posted by 74Argosy24MH

What alternator? Sounds like the sense wire for the regulator on a Delco.

John

Standard high current Delco GM alternator. These require an excitation voltage from the ignition to work but I never heard of a sense wire. By the way these are in all of the Classic Motor Homes up to 1994 or 5 (at least in the Manuals). Airstream checked all of the manuals but has no idea what the wire is for. Neither does my dealer. Airstream is continuing the investigation. My GM RV Motor Home manual shows the wiring diagram for the isolator and they do not show any sensor lead at all. Big mystery.

[74Argosy24MH]

Check it with an ohm meter back to the small red wire in the plug on the alternator. If it is the same wire, it needs to either be tied in with the black/brown wire in the plug or to a terminal that is hot when the ignition switch is in the ignition position.

John

[wa3vez]

Originally Posted by 74Argosy24MH

Check it with an ohm meter back to the small red wire in the plug on the alternator. If it is the same wire, it needs to either be tied in with the black/brown wire in the plug or to a terminal that is hot when the ignition switch is in the ignition position.

John

There are three wires coming out of the alternator plug. One goes to the ignition, the brown wire is just hanging loose and is taped up. I believe this is for a dash charge light. The third wire is a red 16 gage one that may very well be the mystery wire. I have checked Airstream, several dealers, Chevrolet, Workhorse, and GM and nobody can tell me what this wire is supposed to do.

[wa3vez]

I got it and our Motor Homes are wired incorrectly. See new thread "Urgent! Alternator/Isolator is wired incorrectly"