AC Electrical SNAFU

airohead · 09-29-2010, 12:34 PM

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?!

Boyd · 09-29-2010, 12:38 PM

Have you checked the voltage coming from the shore power?

**KyDan** · 09-29-2010, 01:37 PM

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???

BigDTx · 09-29-2010, 03:23 PM

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.

airohead · 09-29-2010, 06:59 PM

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.

Brad

MikeA · 09-29-2010, 08:06 PM

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.

Mike

jimh · 09-30-2010, 06:21 AM

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 anything...to 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.

**Bama Rambler** · 09-30-2010, 07:39 AM

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.

camprat · 09-30-2010, 04:25 PM

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.

kbrown1075 · 09-30-2010, 04:43 PM

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.

jimh · 09-30-2010, 09:12 PM

a simple voltage check inside the trailer can tell u a lot. there is also a circuit tester that plugs into one of the outlets inside the trailer that can tell you if something is disconnected. (they cost abt $3 and look like one of those old adapters that use to adapt a 2 prong (no round ground) to a 3 prong appliance only it has 3 lights on it) only abt 3x longer. you should be able to find one at a lumber yard or good hardware store.

keep in mind, there are two grounds coming into the trailer. one is called neutral and the other ground. they origionate a the same bus in ur home and terminate at the same bus in the trailer. assuming you are going into a 3 prong service at ur home, even if u are adapting to a 2 hot in the trailer (50 amp) and you are wired at ur home correctly, u should have two grounds. the circuit tester will find if any one of the wires is open or connected wrong. you said that u have checked the connections and they are good. one of the comments above was to feel for hot (temperature wise) connections. if you have that, something is still loose. if all checks good, put a load on it and see if it is still good.

oh, also check the outlet that ur pluging into at home. u want to make sure it is correct. (use the little tester discribed above).
i'm assuming that u have this problem away from home as well as at home.

if u check all the connections and there is nothing wrong...even where u plug ur trailer in. then go back to a systematic approach to isolate the problem. if u turn the breakers on one by one and the problem happens on the last one u turned on. trip them all and start with the one that caused the problem. if it happens again, u've isolated the problem to that circuit. if it doesn't ur problem is at the trailer breaker box or before...ie ground or hot wire.

keep in mind, the writers above may have experienced this problem and found what they are telling u is the problem. in my case, i'm still trying to find the problem. there have been a number of post in forems that tell abt connections becoming loose in the breaker box due to either vibration or just not being tightened in the first place. with the power off (unpluged from outside source), check to make sure all of the connections between ur (supply) cable and the breaker box itself are tight.

whatever u find, let us know so we can check that if we get a similar problem.

jimh · 10-01-2010, 06:54 AM

i stole this from another web site. My trailer came with an extremely generic owners manuel. this is abt the same but it may show u what they are doing in there. if it is in the air conditioner, there is most likely a schematic of that system somewhere under the cover.

http://www.cardinalrvclub.org/pdf/30...Schematics.pdf

DAISY BOYKIN · 10-01-2010, 12:05 PM

I read somewhere recently there is a recall on RV 12V Fluorescent lights
that were installed in a lot of RV's. The recall was due to interference with
AC's, Piezo lighters for stoves, Furnace controls, Hot water tank controls.
If my memory serves me right the transformer or start ballast was causing the problem. They could not be repaired but had to be replaced. Even with the light turned off they would still interfere with the above listed equipment.

Also some 12V power inverters were causing the same problem by not being filtered properly.

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