New Alternator Woes

[Sluce]

I installed a new Balmar 70 amp alternator and AR-5 regulator on my Westerbeke 46 engine and have a problem I don't understand at all.
The alternator appears to be working correctly, but...
When I turn on the ignition switch the temperature gauge and oil pressure gauge immediately peg all the way to the right. The voltage gauge stays all the way to the left. This happens before I start the engine and they don't change when the engine starts.
I'm pretty sure I connected all the wires correctly, but obviously I did something wrong. I tried disconnecting the tach and exciter wires at the alternator, but the needles still pegged when I turned on the ignition.
I am at a loss, I don't even know where to begin to track this down. Has anybody seen anything similar or have any suggestions on how to troubleshoot this?
Thanks in advance.

[David M]

If I were to guess at it, you have a 12 VDC positive going directly to your gauges rather than the normal 12v hot going to your engine sensors first and then the reduced voltage going to your gauges.

[Sluce]

I expect that is what is happening. But how could putting in a new alternator have done that? The only wires connecting to the instrument panel are the hot from the ignition switch and the tachometer.

[bmm32005]

I think it has to go to the brown wire off the Balmar supplied harness. I had a similar issue. Give balmar a call too. Helpful for me

[Stu Jackson]

Did you do a before & after wiring diagram, like this?

Alternator Regulator Wiring Diagrams - all three Alternator Regulator Wiring Diagrams (all three)

It's really hard to help diagnose electrical issues with either pictures of wiring only or only text. Wiring diagrams are pretty much the only way.

Good luck.

[FlyingCloud1937]

When a gauge pegs, it is indicative a short between the sender and the gauge. Or a shorted sender.

As a matter of fact that is how to determine if the gauge is good. With ignition on, and sender wire disconnected at the sender, if grounding the wire pegs the needle, then you have a bad sender. if the gauge doesn't move then you have a bad gauge.

Don't leave a gauge on with either a shorted sender/ sender wire, as it will soon kill the gauge.

Lloyd

Originally Posted by Sluce

I installed a new Balmar 70 amp alternator and AR-5 regulator on my Westerbeke 46 engine and have a problem I don't understand at all.

When I turn on the ignition switch the temperature gauge and oil pressure gauge immediately peg all the way to the right. The voltage gauge stays all the way to the left. This happens before I start the engine and they don't change when the engine starts.


I am at a loss, I don't even know where to begin to track this down. Has anybody seen anything similar or have any suggestions on how to troubleshoot this?
Thanks in advance.

[Blue Stocking]

Also check your tach for accuracy. Can't remember if the 2 alternators are 12 or 14 pole, or 1 of each.

[donradcliffe]

Problem is probably in the regulator wiring, or wires you moved to install the regulator. Check it again.

[Sluce]

Thanks for all the replies. In the end I had to get a mechanic to look at it. It turned out that the ground to the instrument panel had become disconnected somewhere in the wiring harness or behind the panel. I had been concentrating on the ground from the alternator, which was fine. I never thought to check the ground to the panel.
He wired in a new ground connection and I was back in business.