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TOPIC: Westerbeke 4.4 very low voltage

Westerbeke 4.4 very low voltage 18 Jun 2017 01:38 #1

  • dpeery
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A couple weekends back, took the boat out for a couple days. First night fired up the generator to run the ac. Everything started up fine, turned on the forward ac. After about 30 seconds the ac stopped. Checked the voltage gauges and no voltage. About 30 seconds later the generator shut down. Not my day. Tried to restart the generator and it ran when I held the preheat switch, but no voltage. (~3 volts)

There was no smoke, smell, or noise, just stopped producing.

Here is what I have found so far.

1) the water temp sensor was shorted to ground. That was causing the shutdown. With this bypassed, the generator runs fine. It was pulling a hell of a current on the dc side. During troubleshooting I jumpered the oil pressure switch and the current just melted the jumper wire. After disconnecting the water temp switch the same type jumper works fine. The ohms to ground was 3.

2) been running through the westerbeke troubleshooting guide, and everything seems to be checking ok. Can't find the source of the problem yet.

a) generator is running 1895 rpm, so that is ok
b) caps seem to be ok. Using a multimeter in ohms mode, they both seem to charge and discharge ok. I have ordered news ones to replace to just to be sure.
c) stator windings are not shorted to case or each other and the ohms for the winding seems to match the spec.
d) exciter winding ohms is also ok with no shorts to case or other windings
e) I have not unsoldered the diodes, so that could be an issue. I measure 4 ohms across the connected diodes, either direction. But this is with the winding connected, and the winding spec is 4 ohms.
f) I hooked up 12v to the exciter winding per the guide. It says I should get 24-28 volts in the ac side with the generator running. I got 18 volts. But, I am not sure this is an issue as the instruction said to hook up to the 50hz wire, and I don't have one, so I hooked to the 60hz wire.

Not sure where else to go with this. I am planning to change the caps, and unsolder the diodes and check them.

Any other ideas?

It's odd to me the failed water temp switch happened at almost the exact same time as the voltage issue. Not sure how those could be related, though.

Thanks!

Dean

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1988 Bayliner 3288
Hino 135s / Water Cooled Turbos
Texas Gulf Coast

Westerbeke 4.4 very low voltage 18 Jun 2017 18:00 #2

  • Sunbird
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Dean,
Do you know if your generator has a full wave rectifier? Most do- it looks like a small square with four terminals on it. Two are for AC connection and two are for D.C. Output. If this unit fails your generator will not produce power.

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Gibraltar, Mi.
1986- 3870- Hino 175's - Just purchased May ,2017
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88 26' Shamrock/ Diesel
14' Zodiac Bay Runner

Westerbeke 4.4 very low voltage 19 Jun 2017 03:52 #3

  • dpeery
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Hi sunbird,

My generator does have a rectifier. According to the westerbeke manual it is only for charging the battery. My multimeter shows odd readings, so I ordered a new meter. It showed weird readings on a new diode as well. I will check it again when the new meter arrives.

Dean

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1988 Bayliner 3288
Hino 135s / Water Cooled Turbos
Texas Gulf Coast

Westerbeke 4.4 very low voltage 26 Jun 2017 00:01 #4

  • dpeery
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Update: got my new meter this week( you can buy a decent fluke-knockoff on amazon for $30 and it works really well).

The capacitors are supposed to be 31.5mf - one measured 33, the other one 22. I am hoping the 22 is my problem because I can't find any other major issues:

1) replaced the flow switch and the generator engine runs fine now
2) unsoldered one of the diodes and checked it, it was good. 0.5V forward and infinity reverse. I didn't check the second one, it would take both to be out to cause my problem.
3) I get about 3.8V and 63hz when the generator is running.(so speed is right)
4) checked the diode rectifier and it is good. No issues there
5) no winding is shorted to any other. Lowest I got was 1meg-ohm.
6) winding ohms are similar to the troubleshooting guide, within 0.5 in all cases.
7) I get 18V on the output when I flash the exciter with the 12V from the battery. Book says I should get 24-28 so this is a concern.

Any thoughts appreciated!

Dean

If the new caps don't fix it, I guess I am looking at a new backend.

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1988 Bayliner 3288
Hino 135s / Water Cooled Turbos
Texas Gulf Coast
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