Alternator problem
 

I changed my alternator last weekend and at the same time I added the "add a battery" from blue sea. Ran a 4 gauge wire from the house bank to the fuse box. This to isolate the engine battery from the rest of the boat and it's accessories.

My problem is with the voltage reading on the gauge. Every time I start the engine and give it a little gas, the voltage reads almost 16 volts. And after maybe 10 seconds or so it returns to around 14 and will remain there. Whether it's cold or being restarted after shutting her down for just a few minutes. It still does the same thing.

Any ideas???

Captain D

Re: Alternator problem
 

Start by taking the Blue Sea Add A Battery system out of the equation and see what it does. I suspect it'll do the same. Talk to the seller or manufacturer of the alternator. Perhaps that's normal behaviour for its regulator. But yeah: 16VDC is quite high. I would be concerned.

Jim

Re: Alternator problem
 

Thanks for your help. I think I'll return the alternator for a new one.

Captain D

Re: Alternator problem
 

Captain D
I recently replaced my alternator as well. When I first start up I get a high reading and then it settles down to the 10-12 range. Even with the bad alternator it did the same thing. I have two batteries but use a Perko switch, I just switch between them so I always have a reserve. I have a few friends with Mariah's as well and everyone of them has either real high guage readings or lower guage readings. I kinda adopted the rule if the guage moves at all it's probably working fine. It seems like the guages are not very accurate. I check the alternator every now and again to make sure its good, and just go about my day. I don't have any experience with the system you installed, but I would not put a ton of stock on your guage being super accurate.

Re: Alternator problem
 

If your old, bad alternator and your new alternator were reading the same voltage output, that should tell you that perhaps something's amiss with the new alternator. 10-12V is way too low. You should see 13.5 to 14.5 volts with the engine running. Heck, a fully-charged "12V" automotive battery reads 12.6VDC. Were I you: I'd buy a decent digital multimeter (Harbor Freight has, or had, a half-way decent "automotive" one for casual use for around $50 - and it would measure RPM) or borrow a decent DMM from a friend, and check.

Btw: I haven't checked Shazaam!'s voltmeter against one of my DMMs, but the reading it shows me is in the right range, around 14V or so, for a correctly-functioning alternator.

Jim