We've put about 2000 miles on the coach in the past three weeks, and I've noticed that the volt meter on the dash moves around quite a bit. When I start in the morning I see a reading of around 14v. As the morning goes on the voltage drops, sometimes to around 11v. At the lunch stop it goes back up. I normally drive with the headlights on, but since this has started happening I've left the headlights off unless it is raining. Today, twice, I saw the voltage jump up to over 15v briefly before dropping back to 12v.
Questions: what voltage is that gauge actually reading? Am I looking at a new alternator, new voltage regulator, or both?
David,
First thing to check would be the alternator sensing wire. Make sure it is not broken and the ends are clean. There is a breaker somewhere in that line make sure it is good. The breaker is noted for getting corroded and not letting proper voltage get to the voltage regulator on the alternator. This is one cause for a voltage swing as you describe and the cheapest to repair.
Pamela & Mike
Not to hijack the thread, but I just had my alternator rebuilt as it wasn't working, stator and regulator mostly fried. I checked all the battery connections and the isolator connections and it seems to be okay. Any idea Mike where the breaker on the sense wire would be on a 96 U270?
Jerry,
It should be located on the same panel as your battery isolator. Should be hid on the frame rail just behind the left rear tires. It should have been originally wired to come off the aux start solenoid. If you look at your B-2126 print you can see it in the lower left corner. Several have moved this wire to come directly off the battery or where ever they determined was the best place for there needs.
Pamela & Mike
David,
You DO have a problem. It could be a gauge issue, but you need to pull out your voltmeter and check voltage when you get abnormal readings. Check at either the two outer lugs of the battery isolator or at the batteries themselves.
I agree that a loose or poor connection of the sense wire (chassis battery lug of isolator to alternator sense terminal) is a good place to start.
You need to solve this, as 11-15 VDC is really hard timing a lot of your 12 VDC equipment, if indeed voltage is fluctuating that much.
Might be time to get a reasonable DVM and start checking, other wise your guessing .
Guessing is good, it adds to the confusion.
Will this fluctuating voltage affect battery life?
Sure. Over or undercharging shortens battery life.
Same thing with us turned out to be the voltage regulator in the alternator. Hardest part of that repair is removing the alternator. Be sure to have the new regulator set for the voltage that's correct for your battery type. ;)