New AC problem

[jjrbus]

 With your help I troubleshot my 13.5K  Dometic Brisk Air roof air. The problem was the compressor relay on the circut board. I disassembled the old one and the points were welded together. I ordered new one from Nick,it showed up in a timely fashion and I installed it.
Everything works fine, The compressor comes on, the fan comes on, the fan has hi and low. Everthing is good. Except if I put the fan in the on position. It will not start.I can here the fan relay on the circut board click, the fan motor tries to start, I can hear it but just wont get going. Works fine in the auto position. It would not be an issue but I do use the fan to help distribute the air from front AC.
Any thoughts, ideas, suggestions, opinions or wisecracks greatly appreciated. Jim

[Nick Badame Refrig/ACC]

Hi Jim,

It sounds like the auto position is hi speed and the on position is low speed.

Hence, the low speed of the motor is dying on you... if will shift to low speed fro hi, but not low speed by it's self.

Not too bad of a problem for an older unit but, the motors are a Bi**h to replace if the shafts are rusted.

Nick-

[jjrbus]

Thanks Nick, you are probably right. I think it is time to throw in the towel on this one. I paid $250 for it 7 years ago, it owes me nothing! Better to just watch for a sale on a new one.

[TomC]

I know on my Coleman A/C's, the fan runs continuously once turned on.  If the fan works on automatic, then just turn the thermostat up high enough so the compressor doesn't come on.  Good luck TomC

[jjrbus]

 Good thinking Tom. On the Duo Therms the fan shuts off, but thanks.

[Sojourner]

Jim..........try turning fan by hand while in "on" position. If it take off...than a bad fan capacitor or if it "growling" ...worn out bearing or "turning hard"....rusted or no lube. And for good insurance is replace both capacitors while you are at it if it it's.

And check line voltage while under heavy load such as compressor & fan in starting mode before the running mode and at the same time refrigerator in starting mode and whatever electrical appliances on and running.  Otherwise it can shorten the relay life and use more electricity than you need to get cooling down time shortened or quicker.

Your earlier post mentioned 121v which is good BUT.....BUT is it with every heavy current user on as I stated in the above paragraph? If not replace power cord for heavier ones or shorten it to the needed length into two sets of cords and make sure every power connections is near or as cool as ambient air temperature under heavy load with infrared temperature gun or with your hand if it is safe. If anywhere along power circuit is warmer then the rest...replace with heavier wire or box or tighten or whatever.

The bottom line is whatever your main circuit load is (30a or whatever), you should not have more resistance then it is designed such as  30a @ .2 ohms (6v drop) or even better .1 ohm (3v drop) resistance. Get your digital ohm meter & check it out...for your peace of mind Unplug power cord from main pole & bring it near A/C plug-in & check ohms of each line. Do this ohm check right after all wire circuit is warmed up from running....it should be less than point 2 (.2) or less ohms. Analog meter is more difficult to read finer measurement.

Wire Resistances link:
http://www.radiolocman.com/electrical-engineering/circuit-cache.html?di=18899

Heat damage is caused by lower as well as too high than normal load voltage Will cause burn points &/or damaging capacitors.

FWIW

Sojourn for Christ, Jerry