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Old 09-29-2010, 01:34 PM   #1
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AC Electrical SNAFU

I have a 1999 Sandpiper 27" 5th wheel bunkhouse with with a peculiar electrical problem regarding the AC.

I can only get the AC to work occasionally (rarely when it's hot out). If I have it working and turn on the range hood (rh) light or fan switch the AC shuts off entirely and can't be restarted, nor does the rh fan work. Then, when I turn the rh fan or light switches on the reset light on the hotwater heater comes on at about half power (brightness). If I play with the rh switches, turning them on and off in various combinations I can get the h2o heater reset light to barely show and only then can I get the AC/heater blower fan to work but no cold air. It can be days or weeks or even months before the AC will suddenly come on again.

Even when I avoid the range hood the AC will work one day and the next time I switch it on....nothing.

I have checked all the wiring on the AC unit and checked, cleaned, and retightened the wires at the breakers.

Any help out there?!

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Old 09-29-2010, 01:38 PM   #2
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Have you checked the voltage coming from the shore power?

"If everything seems to be going well, look around, you've obviously overlooked something."
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Old 09-29-2010, 02:37 PM   #3
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I suspect a 12v issue.
The thermostat in my trailer operates the furnace on 12v without
shore power so I --guess-- it uses 12v to signal the AC to come
on when I am on shore power.
Since you are having all these problems with your other 12v items
I think you have problems there.
Do you have a battery in your RV?
Sounds like the 12 volt voltage is low possibly indicating some
sort of problem with your power center/converter.
Have you checked your 12v with a meter at the panel???
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Old 09-29-2010, 04:23 PM   #4
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Sounds like you have a short somewhere in 12V system, when you say the light for the H20 heater will light up but dimly, it makes me believe you have a short within the harness for the Range hood and it is shorting to the H20 circuit. this will cause the type of symptom you are talking about (brightess of the indicator light), also a low voltage issue can cause this fault.

There may be more than one problem.

There is also a start up relay or capacitor on your AC that controls the compressor turning on, it may be faulty if all you get is the Fan blowing and no cold air.

Sorry i have no actuall fix for your problem, it will require some trouble shooting and wire chasing to find the fix.

Have you tried a volt meter to see if you are getting 12V to your 12V appliances? I would start there with a meter and check circuit voltage. If you can get tothe compressor leads on your AC I would check the 110V going into the compressor start relay and check for 110V at the copmpressor also.
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Old 09-29-2010, 07:59 PM   #5
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Thanks for your reply. All the 12V units seem to be working fine althought I'll test them to make sure that they are at a full 12 volts.

I'll see if I can find the start up relay/capacitor for the AC as well.
Is there any trick to testing it for proper function?

And, finally, any idea where I might find a wiring diagram/schematic for this model?

Thanks again for your help.

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Old 09-29-2010, 09:06 PM   #6
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It seems to me that the AC and the range hood wiring are crossed somewhere. I would check the wiring in the converter to start. It is the only place I can think of where the line voltage and 12V are intentionally in the same area. The only other thing I can think of is the possibility that the somebody confused the wiring of the wall thermostat (if you have one) as it is a low voltage circuit.

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Old 09-30-2010, 07:21 AM   #7
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try tripping all the breakers except the one to the air conditioner and see if it gives the same problem. if it works ok, try turning on the breakers one at a time until the problem reappears. i'm thinking the hw heater and air conditioner are exerencing low (110) voltage. my line of thinking is that the the air conditioner fan will run but the compressor won't come on with low voltage (this is speculation).

i would like to know what the 110 voltage in the trailer is reading when this is happening. the a/c supply would be producing the dc as well. (110 usually runs ~ 120v to 125).

if the problem persist, try unplugging the converter (i'm going to assume the bat is fully charged and will supply the dc). if the problem disappears with this, it may be the converter (i would try and duplicate any "fix" many times before i went out and bought me the converter is a long shot).

an afterthought on tightening connections, you could have connections along the way on ac or dc. with ac, like on ur outlets, u could have one coming in and one leaving to another outlet. i wouldn't expect this with the a/c or the hw heater. the dc, maybe. just store it away somewhere while ur troubleshooting.
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Old 09-30-2010, 08:39 AM   #8
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Sounds like a loose intermittent ground connection either at the shore power plug or at the converter. As soon as it sees a little load it opens causing all the strange problems you're seeing.
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Old 09-30-2010, 05:25 PM   #9
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I agree with Bama. I would start at the outlet work your way back, check the plug is it over heating, check at the panel with power off for loose connection on the neutral, hot too. If it check out. i would pull you main breaker look at the breaker & buss where in clips in.
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Old 09-30-2010, 05:43 PM   #10
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My thought is possibly a bad switch at the range hood. A partial connection causing a lower voltage to the fan and/ or light causing an increase in amperage. Just a thought.

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