7.0 Westerbeke won't run my A/C units

RobnBern

RobnBern

Member
Jan 24, 2010
212
Upper Potomac River
Boat Info
2015 470DA
Engines
Cummins 480 with Zeus
Hello,

We've got a "new to us" '95 370 and we've got a bit of a gen problem. She fires up, runs smooth as silk but doesn't seem to have enough juice to run either of the AC units, much less both and that's with NO OTHER draw on the system. Seems to only happen with the AC units, as everything else works fine. When I'm at the dock, the AC will freeze you off the boat.

Finally got hold of the old owner and he said he rarely used the gen. In fact, I shockingly discovered, he hadn't tuned the boat since 2007. So, in addition to new wired, plugs and caps for the engines, I'm probably going to need to do the same for the gen.

Beyond that, tho, does anyone else have experience with a similar problem with their gen? The 3H's of Washington DC summers have arrived very early....Hazy!! Hot!!! Humid!!!

Thanks, boat safely, and MY LORD be careful on the fuel dock. A boat at the marina just up from us caught fire just after fueling this morning. It was incredible to watch.

RJ....
 
I don't know if this will help but I had a problem with A Gen
and I pulled the inspection cover that was over the brushes
and had some corrosion & dirt on it I took some sand cloth
and cleaned the Armature and what A difference In voltage.
 
Tom,

Thanks for the reply. The boat and all is new to us, so I'm not sure where the inspection cover may be located. I am thumbing thru the manuals and can't see it...but I'm tired so I probably am just missing it.
 
I have the exact same boat with the same generator and the same AC units and I can tell you that when the generator is running correctly it can handle the load of both the units plus the rest of the house load like the water heater and the fridge. A couple of suggestions: make sure the generator is warmed up before you load it with the AC units. You also must get the the front AC unit going first as it is much larger than that aft unit. Keep in mind that you must have both of the circuit breakers for the AC units turned on and then use the control panels to first turn on the front unit and then the back unit. The raw water pump that services both of the units is wired on the circuit for the aft unit so the breaker for the aft unit must be switched on even if you are only going to run the foward unit. Lastly you must make sure the generator is running properly and generating sufficent voltage. My generator tends to fowl the spark plugs over the season and once the plugs are bad enough it will not longer handle the load of the two AC units with out the front unit tripping out with a LO AC warning for low voltage. Changing the three plugs is a PITA. Dont even try it without buying a plug socket with a swivel. If I were you I would start with changing the plugs.
 
There are no brushes. The armature windings are self-exciting. There's a separate set of exciter windings in the stationary coil that's maintained by an L-C circuit that has a large, calibrated electrolytic capacitor.

First thing to do is to check the output voltage of the genset. No load voltage should be around 125 or so. Also, check the RPMs. The easy way to check RPM is by using a digital voltmeter (DVM) with frequency counting capability. You want to see about 60 Hz +/- 3 Hz, I think. I forget the exact spec, Rod still has my service manuals, so I can't check, but that'll get you started.

If no-load is good to go, throw on a purely resistive load like the water heater, which probably draws about 10 amps. Voltage and frequency shouldn't vary much, maybe a drop of 5 to 7 volts, but still around 117-122.

Next step depends on what those tests show. The service manual has a nice diagnostic chart. If you're going to do this, get yourself a decent DVM, like a Fluke. I have an HP, but they were spun off and are now Agilent. Good stuff, but not cheap.

Best regards,
Frank
 
Last edited:
RJ,

When you say it won't run the ac units.....what do you mean? Do the breakers trip....does the generator shut down....what is going on? As fc3 noted, a good dvm will help sort this out.

-John
 
PlayDate said:
RJ,

When you say it won't run the ac units.....what do you mean? Do the breakers trip....does the generator shut down....what is going on? As fc3 noted, a good dvm will help sort this out.

-John
Click to expand...

Hi John and others

this information is awesome. Some of the technical end, I'm not sure I'm prepared to tackle alone. To answer your questions:

The breakers do not trip.
The gen does not shut down.
I get the Lo AC code and then the forward AC shuts down then comes back on...

So, based on what I think I can tackle, I'll change the plugs and stuff. I need to replace them on the mains anyway, as I just learned the boat hasn't had any tune up since 2007ish.
 
Why wasn't the lack of maintenance and genset problems discovered before the purchase?
 
RJ,

It may be more of an adjustment issue than anything else. Go ahead and change the plugs and post what they look like.

Your Westerbeke either has a mechanical (belt driven) or electronic governor. In either case, you can adjust the "gain" so that it responds quicker to a heavy load. If it is set too low.....the generator takes too long to increase power to handle a heavy load and th result is low ac output. Too high of a setting and the generator starts "hunting" and does not acheive a constant rpm.

I would hit the plugs first. If it still acts up....I can walk you though the gain adjustment.

-John
 
It has a belt driven mechanical governor. Speaking of which you should check the oil level in the governor, I think there is a 500 hour interval to actually change the oil in the governor. I did it a few years ago.
 
wow fc3 said it best i would do that first adjust the rpm to achieve the right voltage with all loads turned on I don't like to see any thing less than 112 volts
 
I have been troubleshooting my Onan 3kw gennie for a week now. It would shut down after about 5-10 min under load. It would slowly lose rpms and finally just quit. I just put in a new spark plug and it ran perfectly under load for 45min. I am hopeful it is fixed . Put in new plugs ASAP and report back.
 
Hey all, just an update. After reading stuff here, I slid down to the marina today and fired up the gen and guess what!! She only puts out 105 volts. Explains why I can't run everything. So, I'm hoping the tune up, new plugs etc will help. Any other suggestions?

Robin
 
Well my gennie shut down again today after just a few minutes so my new spark plug did not fix it....damn. Good luck with your's , I am back to troubleshooting.
 
In addition to all the very good suggestions mentioned above, I also suggest to put a new carburator kit. Two years ago my gen was not able to hold the load and would die after a while. Installing a new carburator kit solved the problem. You may not have this problem now but since you are doing a tune-up why not doing it now.
 
Also, the A/C system has a voltage tolerance setting. If this has been set too high by accident, you could be chasing a non problem.
However, if the plugs haven't been changed since 2007, just do them all anyways.
I purchased a very inexpensive voltage/frequency monitor that I used to adjust my generator governer settings. You can search here for other threads about it.
http://www.amazon.com/P3-International-P4400-Electricity-Monitor/dp/B00009MDBU
 
RobnBern said:
Hey all, just an update. After reading stuff here, I slid down to the marina today and fired up the gen and guess what!! She only puts out 105 volts. Explains why I can't run everything. So, I'm hoping the tune up, new plugs etc will help. Any other suggestions?

Robin
Click to expand...

A "tune up" won't help here. If it's putting out 105 volts, the gen is likely not running at the correct rpms to achieve the necessary 60 hz. This would be a governor issue.
 
RobnBern said:
Hey all, just an update. After reading stuff here, I slid down to the marina today and fired up the gen and guess what!! She only puts out 105 volts. Explains why I can't run everything. So, I'm hoping the tune up, new plugs etc will help. Any other suggestions?

Robin
Click to expand...

Do the tune up, but you'll probably need to adjust the governor. You must use a tachometer or a frequency counter to adjust the engine RPM. Do not attempt to set the engine speed by output voltage alone!

Do not attempt to adjust the governor without consulting the manual! The manual is available on-line from Westerbeke. Download it, read it over and over until it's clear and you understand the process, cautions, and pitfalls. Some of the setting, if maladjusted, can damage the governor. The BCGTC series governor is $611.

Best regards,
Frank
 
tobnpr said:
This is one that I'd pay the mechanic for a trip to the boat...
Click to expand...

Yeah, after reading the list of possible issues, I have scheduled the trained wrench to come look at the patient. I'll just do the plugs etc on the twin main engines and leave the gen to someone who has a clue.
 
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