A/C tripping breaker

M

Matt@fullcount

New Member
Nov 25, 2020
27
Boat Info
1990 Sea Ray 390 Express Cruiser
Engines
2006 mercruisers
Our air conditioner worked great all summer but recently started tripping the breaker after running for a few minutes. No water is coming out of the side of the boat. We have a mechanic potentially coming out next weekend, but would appreciate any troubleshooting tips as we learn how to fix things ourselves. Thanks and Merry Christmas!
 
Where is the boat located ? No info in Bio. Have the a/c raw water lines been flushed/cleaned lately ? No water flow would indicate plugged cooling lines and or strainer basket. If the a/c unit does not receive proper cooling water it should automatically shutdown due to high head pressure. If you still have the original 1990 unit it may trip the breaker due to high amp draw due to lack of cooling water.
 
We are currently in Key West, down from Michigan. I think we have the original unit. We will figure out how to flush the lines. Thank you. Boat is new to us in May. Thanks a lot!
 
Check the water supply right off the bat. Insufecent water will make the ac unit kick off line but that should take place before enough amperage is generated to trip the breaker. If all else fails check the breaker itself. Just replaced my 120/50 amp breaker. It was shorting out internally. Got me how or why but that's what my load meter told me and swapping it out was the cure. Might be the same for your ac breaker.

Hey, it's a boat.
Meanwhile; have a fantastic Christmas in the Keys
 
Thanks everyone! We will check pump and lines and report back. Much appreciated!
 
Are you getting a message at your panel? As others have stated your compressor is the next thing to check after you confirm sufficient water flow. Changing out the unit is a fairly simple DIY project. If the unit has lost the Freon then you can get it charged but you are going down the same road I am. I had mine re-charged this year but once your unit needs re-charged then you have a leak and the cost to get someone in to rebraze the lines is not worth he cost on a unit that age.
 
If all of the water checks are OK, a starting capaitor for the compressor might be something to check into before changing out the compressor. Heed the advice of others ... you need waterflow before the compressor attempts to start.
 
electricaldoctor said:
If all of the water checks are OK, a starting capaitor for the compressor might be something to check into before changing out the compressor. Heed the advice of others ... you need waterflow before the compressor attempts to start.
Click to expand...

If it was starting and running for a bit, I would think either the run cap. If it is an older unit the windings may tired.
 
There are three independent circuits of which two (fan and compressor) are on one circuit breaker and the raw water pump on another. I believe some of the smaller systems are on a single circuit breaker. When the system is turned on first the fan should start then the raw water pump then compressor. There are sensors that will shut down the system should any one of the three fail to perform it's function but unless there is an overcurrent (short) condition will not trip a circuit breaker. So, it sounds to be that you may have two conditions; one - no raw water flow and two - an overcurrent condition. The system could be demanding raw water and the pump have a fault and trip the circuit breaker but typically that is a separate circuit breaker and/or there is a fault in the compressor wiring / failed start cap....
 
Okay so we have flushed the lines and checked water flow, sea cock etc. everything fine. Then checked electrical current to water pump and it was fine. Took apart pump and impeller is spinning. Primed pump with water through funnel. Can not get water through pump. Only can get water flow all through system and out of boat when bypassing pump. So bad pump?
 
Forgive me for jumping in here...you mentioned that you checked the sea cock and flushed the lines. Three questions: #1. Did you take a shop vac and blow backwards from the sea cock down through the thru-hull till you hear the bubbles coming out from under the boat? Second question: With the sea cock closed, and the strainer "lid" off, have you flushed/forced water through the hull discharge port (don't know if you have one or two, but do all you have) till you have good flow spilling out of the top of the strainer? #3. Have you visually checked the condition of the impeller? It should just be a bunch of screws to remove the plastic cover to check. (I think you did this)

Good luck! I wish I was working on my boat right now. It's 29 Deg F right now with the low going down to 19.

Jaybeaux
 
Jaybeaux said:
Forgive me for jumping in here...you mentioned that you checked the sea cock and flushed the lines. Three questions: #1. Did you take a shop vac and blow backwards from the sea cock down through the thru-hull till you hear the bubbles coming out from under the boat? Second question: With the sea cock closed, and the strainer "lid" off, have you flushed/forced water through the hull discharge port (don't know if you have one or two, but do all you have) till you have good flow spilling out of the top of the strainer? #3. Have you visually checked the condition of the impeller? It should just be a bunch of screws to remove the plastic cover to check. (I think you did this)

Good luck! I wish I was working on my boat right now. It's 29 Deg F right now with the low going down to 19.

Jaybeaux
Click to expand...
Thanks for jumping in! To answer your questions, we did not use a shop vac to blow down through sea cock but when sea cock is open there is plenty of water. We have used dock hose to put water directly into pump when running. Impeller is spinning but won’t push water through system. #2 We flushed lines from outtake hose of pump through the discharge ports and got good flow. #3 Visual check of impeller after removing doesn’t reveal anything obvious. We are thinking maybe pump motor just isn’t running strong enough to push water through system? Not sure what else to try beside replacing pump.
 
Nater Potater said:
Water pump motor could be running fine with no load on it (as in, sitting dry in your hand), but either stall under load, or the impeller could be loose on the motor shaft.
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That’s what seems likely from our view. Impeller looks tight on shaft when replaced and we put some manual pressure on it with handle of screwdriver while spinning and it seems to keep up but when we use hose water or water poured though funnel, it doesn’t pump it though.
 
Matt@fullcount said:
That’s what seems likely from our view. Impeller looks tight on shaft when replaced and we put some manual pressure on it with handle of screwdriver while spinning and it seems to keep up but when we use hose water or water poured though funnel, it doesn’t pump it though.
Click to expand...
Yikes! Well then, I'd have to go with the other comments about plumbing obstructions. How about the heat exchanger itself? It sure sounds like there's something in the water loop that's stopping it. Is there any way you can separate both lines from the pump and see if it'll actually circulate apart from the system into a bucket? That'd at least tell you if the pump itself was capable.
 
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