Burned up Coleman Mach 15 control box..

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.

Sabre2th

Member
Joined
May 17, 2017
Posts
8
Hello!
I have a "toasted" control box on my Coleman Mach 15, trying to figure out the cause.. History: A few weeks back I was having trouble with my AC unit (ducted) on our Bounder 32H throwing the breaker and it finally stopped cooling altogether.  I took the simple (and best, I think) route and just replaced the whole unit.  This last week, I went out and turned the AC on to get it cooling for a short trip this weekend.  When I went out to stock the fridge on Wednesday, I noticed that the air wasn't working.  I dug into it a bit and found that the incoming power side of the circuit board in the control box is completely burnt.  Has anybody here had this issue?  Could this be a residual issue from the previous unit?  A problem with the new unit?  Just a power surge?
Any ideas/suggestions as to what I should check?  Pretty handy with a multi-meter and troubleshooting. 
Thanks!
 

SpencerPJ

Well-known member
Joined
Nov 1, 2017
Posts
4,029
Location
Midwest
What is your power source?  If it is 15A from your garage, and running a AC, might be putting a hard struggle on components.
 

Sabre2th

Member
Joined
May 17, 2017
Posts
8
30 amp.  I've wired a box connected to 30 amp breaker on my main service pole, also a 30 amp circuit inside my shop building for winter storage.
 

John From Detroit

Well-known member
Joined
Apr 12, 2005
Posts
26,268
Location
Davison Michigan
One issue with 30 amp is A line that reslly bothers Me I see all the time.

"I plugged into the house using a 30 amp to 110 adapter"

We went fro 110 to 115 and now 120 decades ago. and 30 amp IS 120 volts so how do you adapt from 120 volts to 120 volts? (The adapter is 30-15 AMP)

Many electricians install a TT-30 with 240 volts.. this is not the way to do it.  And it will damage many of the electronics including but not limited to Microwaves. TV/Radio and other entertainment electronics.  Converters. Refrigerators and water heaters.
 

Sabre2th

Member
Joined
May 17, 2017
Posts
8
John From Detroit said:
One issue with 30 amp is A line that reslly bothers Me I see all the time.

"I plugged into the house using a 30 amp to 110 adapter"

We went fro 110 to 115 and now 120 decades ago. and 30 amp IS 120 volts so how do you adapt from 120 volts to 120 volts? (The adapter is 30-15 AMP)

Many electricians install a TT-30 with 240 volts.. this is not the way to do it.  And it will damage many of the electronics including but not limited to Microwaves. TV/Radio and other entertainment electronics.  Converters. Refrigerators and water heaters.

I could see that happening, for sure.  Mine are wired correctly with proper RV Boxes, 120 volt, 30 amp breakers.  I've kept this motor home plugged in either outside or inside my shop (both proper 30A) for the last 5 years.  This is just a new issue that cropped up after my old AC unit crapped out and I installed a new one..  The new Mach 15 unit was working fine for a couple short trips, the control box burned up (AC power side of the board) when I turned it on last week.  Before installing the new control box, I intend to at least pull the cover off the unit and inspect for wiring, motor, or capacitor issues.
 

regval

Well-known member
Joined
Jun 4, 2015
Posts
426
Location
Lawrenceville, Georgia, USA
The problem may be due to low voltage feeding the Air conditioner control board. The lower the AC voltage feeding the air conditioner compressor and fan motor, the higher the current the motors will draw. The higher current and subsequent heat at the control board terminals may be the cause of the toasted board. I suggest you disconnect the coach from your power source, measure the AC voltage at the recepticle where you plug in your coach, then turn off all electrical in the coach and plug the coach's power cord in.  Measure AC voltage inside the coach at an outlet and turn on the microwave or plug in a hair dryer and see if the voltage drops from what you measured at your power source . Basically you want to simulate the power load of the AC unit and determine if there is a faulty connection that is dropping the power voltage coming into the coach. If your measurements of the power voltage show the same voltage, within a couple of volts, I would then inspect the wiring at the coach's internal circuit breaker panel for loose connections at the air conditioner's circuit breaker. If the voltage is much lower during testing then you will have to isolate the cause, such as a faulty coach power cord, cord adapter, house / shop recepticle or main panel wiring feeding the coach recepticle.
As always, be safe around electrical circuits and always power off when accessing panels.
Good luck
 

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
76,131
Location
West Palm Beach, FL
Is this a two-zone cooling system and the controller in question is a zone control?  And not replaced when the new a/c was installed?  If not a multi-zone system, then was the burned controller a component of the new a/c? If the latter, can you inspect the old controller to see if it too is burned?
 

Henry J Fate

Well-known member
Joined
Jun 14, 2018
Posts
1,978
Definitely check all your internal wiring. Suspect any connections using wire nuts. Those babies almost burned my coach up. I replaced all I could find with lugs. Wire nuts work great in homes but in mobile installations, not the best choice. As Regval suggested, check all the connections.
 

Sabre2th

Member
Joined
May 17, 2017
Posts
8
regval said:
The problem may be due to low voltage feeding the Air conditioner control board. The lower the AC voltage feeding the air conditioner compressor and fan motor, the higher the current the motors will draw. The higher current and subsequent heat at the control board terminals may be the cause of the toasted board. I suggest you disconnect the coach from your power source, measure the AC voltage at the recepticle where you plug in your coach, then turn off all electrical in the coach and plug the coach's power cord in.  Measure AC voltage inside the coach at an outlet and turn on the microwave or plug in a hair dryer and see if the voltage drops from what you measured at your power source . Basically you want to simulate the power load of the AC unit and determine if there is a faulty connection that is dropping the power voltage coming into the coach. If your measurements of the power voltage show the same voltage, within a couple of volts, I would then inspect the wiring at the coach's internal circuit breaker panel for loose connections at the air conditioner's circuit breaker. If the voltage is much lower during testing then you will have to isolate the cause, such as a faulty coach power cord, cord adapter, house / shop receptacle or main panel wiring feeding the coach receptacle.
As always, be safe around electrical circuits and always power off when accessing panels.
Good luck

Will definitely do that!  I'm considering installing a voltage gauge at the main panel as well.  The new control box hasn't arrived yet, but I was looking things over a bit while it was cool out this morning.  I noticed that the 30A plug prongs have a lot of "arc spots" and blackening, so going to replace that cable end before testing anything.  (I suspect it has been getting plugged/unplugged without throwing the breaker when the yard gets mowed)  Might as well start with the obvious before testing anything else..

 

Sabre2th

Member
Joined
May 17, 2017
Posts
8
Gary RV_Wizard said:
Is this a two-zone cooling system and the controller in question is a zone control?  And not replaced when the new a/c was installed?  If not a multi-zone system, then was the burned controller a component of the new a/c? If the latter, can you inspect the old controller to see if it too is burned?

Single-zone, and I had to use the controller from the old unit, mounts on two screws up in the unit.
 
Top Bottom