Westerbeke 7.7 with model 21 dies when a/c is turned on

Darrell Chapell

New Member
Jan 16, 2018
10
Boat Info
1982 355T w/ diesel
Engines
diesel detroit
My generator dies when I turn on the a/c units. will run all day as long as I don't turn on the a/c units. Rear unit pulls 19 amps on line 1, but it runs the pump as well. front a/c on line 2 pulls 11 amps. I can turn on anything and everything except the a/c units. I can even run them by themselves. I can even run the rear only. I can't run the front a/c without the rear on for it tells the pump to come on. Which I am going to change eventually. But in the meantime can anyone help. Thanks
 
19 amps seems awfully high for the rear unit. are your units 110 volt or 240. If you are 110 volt system, just the 2 units are probably over powering the generator.
 
I'd look at the rear unit. I also agree that 19amps seems pretty high. My unit only pulls 10amps with the pump.
 
Thanks, I just looked up the specs on a new 16000 btu unit and it pulls 11 amps. but 19 amps does seem high. I looked up the pump specs and it should only be pulling 1.7 amps. I'm leaning toward the pump. I just got the boat so I have a few things to work out. It may not be the gen.
 
I'm not a electrician and I might not understand how things actually work...... but you would think it would trip the breaker somewhere if it was drawing that much power vs shut down the generator.
 
I talked to a mechanic today and he said that the compressor on the a/c is about to go out. So new a/c is about to be purchased.
 
A buddy of mine was having simular issues after he bought a 2005 420 SB. So he bought a new solon A.C.. it set him back a bit but still had start up issues like you are describing... But it worked better than the old one. Several months later he replaced his house batteries and mysteriously his new A.C. unit works perfect every time. He was a bit pissed he was sold a new unit via the service guy. So just putting that out there. How old are your batteries?

If your batteries are old and need a consant charge that adds amps to the start up on the A.C. knocking it down or out due to low voltage. (Not sure why that is). If my batteries are in a bulk charge via the geny, my main A.C. unit struggles to come on line. I am not an electrician, just describing what we have experienced and resolved.
 
I talked to a mechanic today and he said that the compressor on the a/c is about to go out. So new a/c is about to be purchased.

I believe that is the right answer. Clearly the load on that compressor is a problem. Normally they start tripping their electrical breaker when on shore power as well. The generator is far more load sensitive than shore power. You didn't mention how many hours were on the generator but their ability to handle heavy loads does decline over time.
 
A buddy of mine was having simular issues after he bought a 2005 420 SB. So he bought a new solon A.C.. it set him back a bit but still had start up issues like you are describing... But it worked better than the old one. Several months later he replaced his house batteries and mysteriously his new A.C. unit works perfect every time. He was a bit pissed he was sold a new unit via the service guy. So just putting that out there. How old are your batteries?

If your batteries are old and need a consant charge that adds amps to the start up on the A.C. knocking it down or out due to low voltage. (Not sure why that is). If my batteries are in a bulk charge via the geny, my main A.C. unit struggles to come on line. I am not an electrician, just describing what we have experienced and resolved.


That's very interesting, I've never heard of that situation. I just got the boat so I'm going thru all the systems getting them current in maintenance. I think I'll check the batteries and 12 volt charging systems next. thanks
 
I believe that is the right answer. Clearly the load on that compressor is a problem. Normally they start tripping their electrical breaker when on shore power as well. The generator is far more load sensitive than shore power. You didn't mention how many hours were on the generator but their ability to handle heavy loads does decline over time.


I think it has about 2000 hours on it. I've been watching the rear a/c unit real close and it has started freezing up now and when I run just the fan. It actually cuts completely off even on shore power. So I'm thinking this unit is done for. It's original from 1982.
 
The coils on the ac unit are freezing up? Does it work on heat mode?
Maybe it is overcharged or your reversing valve is sticking causing the compressor to work too hard.
 
I have noticed when my generator is cold and I turn on the air-conditioner it’ll Bogg down not kill the generator but it resets the AC After the Genny runs for about 10 minutes and gets warm that every system works perfectly fine only in the beginning anything that draws a quick 20 A on the start up wI’ll bog down the generator Westerbeke 4.5
 

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