Overvoltage problem

Rv6 with automotive alternator and voltage regulator. Recently started showing 15.3 volts when alternator switch is on. Is this the regulator or altneator problem?

Limited information

With the limited information you gave, and assuming the voltage is reading right, it points to a regulator problem. But i think most regulators fail differently than just creeping up in voltage, depending on type. I would also suggest you check all the grounds. A voltage drop across the grounds, like due to corrosion, might also cause the voltage to creep up.

Yes, it is a voltage regulator problem. But there could be a bad electrical connection in the voltage regulator circuit. Check all connections, both hot and ground. Also check resistance of the alternator on-off switch contacts.

Ok I checked all connectors and grounds. Picked up and installed a new regulator with the same results 15.2 volts. 12 volts going in the regulator and 5 to 7 coming out going to field after start up. It?s like alternator isn?t listening to the regulator. Alternator pulled and going to the ac motor shop for check and a rebuild. Only thing I can think of.

Does the field wire connect to the alt through a plug/socket? If so, inspect the wire/pin joints of all the wires. If they connect at the other end to the regulator through plugs/sockets, check there as well. (This would be more likely to drive the voltage *down*, but it's an easy check; a 1st principle of troubleshooting: check the easy stuff first.)

Also make sure that you have the same voltage on the regulator's sense terminal as the voltage on the alternator's B lead. If you have a high resistance anywhere between the bus and the regulator's sense terminal, the regulator will think the alternator output is low and ramp up the field current. Suspects: wire/terminal interfaces, terminal interfaces, circuit breaker contacts, switch contacts...

It's hard to be much more specific, without more specific info on your devices & wiring. (Generic Ford regulator, B&C regulator, something else? Regulator powered by a wire independent of the sense terminal, or the power terminal and sense terminal fed by the same wire? etc etc)

Charlie

Yes it connects via a plug and socket. Ford type regulator and not sure what alternator it is. I?ll let y?all know what the ac shop says. Thanks for all the help.

Like Charlie said, check the voltage on the regulator "sense" terminal. It should be exactly the same as the voltage on the main power bus. But evidently it is not the same, judging by the symptoms. The alternator can not put out higher voltage than what the regulator calls for. And the only reason the regulator would call for higher voltage is because the sense voltage is too low. The voltage-sense wire should connect the main power bus to the regulator sense terminal. NOTHING else should be connected to that wire or terminal.
There is too much resistance in the regulator voltage sense circuit. The way to find that resistance is to connect a load like a test lamp to the regulator sense terminal, then test with a meter to find where the voltage is being dropped.

Well you gents were right. I added a ground wire to the regulator problem solved. A few profanity laced comments and lots head scratching later it?s fixed. On a good note I now know the charging system and how to use a multimeter. Thanks to the brain trust! Turns out one of the ground bolts was to a nut plate and wouldn?t tighten enough.