Alternator output jumping

[Sebastian DeWitt]

Hey Folks,
the output on my 79 Excella keeps jumping. When I start it, it's OK, but after running for a while, it starts jumping up to 17 volts... the lights flicker, and the fuse to the dash blows. Any thoughts?

Thanks, Sebastian

[overlander63]

Sounds like either the alternator is about to take the big crappolla, or you have an intermittent connection. You can take your MoHo to your favorite garage, and ask them to check the alternator.

[lewster]

Sebastian,

It sounds like the voltage regulator section of your alternator is bad or well on the way. That is what controls the output voltage of your alternator. Also, the rectifier diodes might need to be replaced if they are a separate component and not integrated into the alternator. Any good garage or even a reputable tire center can usually tell by connecting a nifty little gizmo to your battery that checks your alternator output,

Also, if you get a new alternator, be ready for a new battery as well, 'cause 17 volts will fry most lead-acid types.

[Tinsel Loaf]

If it is not a bad connection (most likely not) cut your losses and replace the alternator and regulator. Cheaper in the longrun. End ‘O’ problem.

[ALANSD]

I highly recommend a higher amp rated alternator if you do replace yours. If it is a stock alt its probably 60-70 amps, and a 135 will slide right in and do a better job overall for you. I replaced mine with one from www.4alterstart.com, and used their solid cased aluminum heat resistant starter. I have been very satisfied with both items for quite some time.
I would agree that unless you have a loose connection, your voltage reg is shot, and you should replace the alt at the same time.
Heat kills our alts and starters under that doghouse.

[85/345]

I would start with the voltage regulator, it is the cheapest and easiest part to replace, if I remember correctly cost less than $20 and you can replace it in about ten minutes. I also agree with Alan about using a higher amp alternator.

[swebster]

I agree on checking/replacing the regulator first. It's bolted to the top of the radiator housing. If that's not it then consider removing the alternator and taking it to AutoZone (or similar) as most of these places will test alternators for free. If you need a new one then you're already there.

Like Alan and I also run a higher amp alternator on our 345. It comes in handy then the kids are playing PS2 on the TV and I want to use the inverter instead of firing up the generator.