BK5057 Report post Posted June 18, 2014 When I turn on AC unit after a few seconds there is a pop in the motor and the breaker trips. The fan will not run on fan only and when I turn on the heat pump it just hums. How to test motor and circuit board. Share this post Link to post Share on other sites
dickandlois Report post Posted June 18, 2014 BK, Could you post the year and model of the Dometic AC / Heat pump unit for the group. Will the fan-motor turn freely? The pop sound you mentioned,can you tell if it is coming from AC compressor motor? Rich. Share this post Link to post Share on other sites
BK5057 Report post Posted June 18, 2014 Rich, The AC unit is a 2008 model 630516.331J the fan motor turns freely and the popping sound comes from the fan motor also it blows the breaker when I turn on the fan only. Thanks Bob Share this post Link to post Share on other sites
wolfe10 Report post Posted June 18, 2014 What is the voltage when this occurs-- low voltage will cause excessive amp draw? And is this the CG breaker, RV main breaker or the A/C breaker on the RV breaker panel that is tripping? Share this post Link to post Share on other sites
BK5057 Report post Posted June 18, 2014 Brett All the voltage is good and it's the breaker for the front AC unit in the panel box Thanks Bob Share this post Link to post Share on other sites
dickandlois Report post Posted June 18, 2014 Bob, If you feel comfortable working on the Start and Run capacitors and 120volt AC circuits. Remember they hold a charge and do not want you to fall off the roof !!! Turn off the circuit breaker(s) powering the unit. Look and see if one of the capacitors is deformed or like its leaking. Short out the caps with a screwdriver placed across the terminals, make sure you are only holding the handle(They might ark / spark) If you have a multimeter with a Cap testing setting check to cap readings, also check for a short using the resistance scale. Think that if the motor is turning freely and the voltages are good as mentioned by Brett, that there is a good chance you have a defective starting or run cap. Some of the Motor circuits have a small start module, but that is generally on the AC compressor motor. This is a link to the installation manual and page 19 pictures the wiring circuits, one would expect to see. http://www.dometic.com/1f24ead8-6316-41b6-894c-d01f87ce6bad.fodoc. NOTE! A compressor motor can draw a high current, should it be defective! Rich. Share this post Link to post Share on other sites
BK5057 Report post Posted June 18, 2014 I have nothing at either cap when shorting across. Bob Share this post Link to post Share on other sites
wolfe10 Report post Posted June 18, 2014 Bob, It they are discharged from trying to start the A/C, you may have to turn on the breaker to allow them to recharge before you can accurately determine if they are bad. Share this post Link to post Share on other sites
BK5057 Report post Posted June 18, 2014 Brett Thanks I will try that. After they recharge should they spark if good and not if they are bad? Bob Share this post Link to post Share on other sites
BK5057 Report post Posted June 25, 2014 BrettJust to let you know I got my new parts and after charging the caps I still could not get any spark when shorting out. Changed the caps and still blowing breaker, replaced the motor and good to go everything back to running normal.ThanksBob Share this post Link to post Share on other sites
