RV Repair: rv airconditioner overheat, household outlet, amp breaker

Question
i have a 2006 forrest river salem le with ducted air sorry i dont have a model #, i put the air conditioner on in the morning and it blew cold and there was the normal discharge off the roof. by early afternoon the temperater outside was 105 and you could hear the compr. kick on (large draw of power and  noticable drain and drop off of fan speed) and the air unit would blow cold for 10 seconds then the compr. would stop and the fan would just run at normal speed blowing warm air for about a min, then cold for 10 seconds then warm for a min and it would cycle like this.  no discharge was coming off the roof either.  i turned it off and went to dinner. when i came home around 100pm i tried it again and it worked great, really cold and ran that way for 2 hours.  got up this morning and turned it on and it worked great for a few hours so i turned it off.  when i tried it again at arount 400 pm, temp outside was around 105 again it performed in the manner described earlier.  i had it pluged in to a typical household outlet in my garage with a 20 amp breaker.  is there an overheat switch?  is the unit trying to draw more power than is available during the highest temperature of heat in the day?  im getting ready to leave for myrtle beach and the dealer said his ac guy is on vacation. im just not sure if it is a problem with the unit or its the excessive heat we have had here in nj or lack of adequate power?  seems to work fine until it is really hot outside and you need the ac.  thanks for your help.

Answer
Hi Bill:

Thanks for the great description of your problem with the air conditioner. It seems the only problem with your air conditioner, is the extension cord that you have the rv plugged into. This cord is entirely too small to run the air conditioner. The reason it runs ok when the temperature is cooler is that the higher the outside temperature, the harder the compressor has to work, resulting in higher amp draw. The reason you hear the fan slowing down when it tries to start, is because the compressor is trying to start, but it cannot because not enough power is available, so the compressor trips out on internal overload, then in a few minutes it cools down and tries to restart again. As long as it is turned on, it continues trying to start, until the temperature cools down, then compressor will start again. I would not reccomend ever using a power cord that is too small, as compressor damage will result.

If I can be of further help, please do not hesitate to contact me again.

Regards, Larry