Roof A/C not running - replaced capacitors

Topic: Roof A/C not running - replaced capacitors - what next? (Read 1063 times) previous topic - next topic

Roof A/C not running - replaced capacitors - what next?

October 18, 2018, 09:42:25 pm

Replaced both of the capacitors. Still doesn't run.

Fuse is good.

Is there something else I can check or call a pro?

Looks like a new board is about $150.00.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #1 – October 18, 2018, 10:04:20 pm

Does the fan run?
When you switch the thermostat to cool, and drop temp setting well below ambient can you hear the compressor trying to start?
Is it only one ac unit or both that are not working?

Re: Roof A/C not running - replaced capacitors - what next?

Reply #2 – October 18, 2018, 10:12:35 pm

Hey Chuck -

The fan does not run - even with help.

I did not leave the unit energized long enough to see if the compressor started. Will try that tomorrow afternoon.

We have 3 units. Front, Middle and Rear. The Front and rear stopped around the same time. I replaced the capacitors in the front ac unit and it is running. The middle unit is running fine. The problem child is the rear one now. The front and rear ac units were replaced by our PO in 2011.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #3 – October 18, 2018, 11:44:17 pm

Are you getting power out of the control board?

Re: Roof A/C not running - replaced capacitors - what next?

Reply #4 – October 19, 2018, 12:16:25 am

Thanks to Steve and Michelle as I found the wiring diagram in OUR Library.

And sedelange....

Next opportunity I will get my DVM and start to follow the power. ARGH

Re: Roof A/C not running - replaced capacitors - what next?

Reply #5 – October 19, 2018, 07:32:19 am

Quote from: sedelange – October 18, 2018, 11:44:17 pm

Are you getting power out of the control board?

And do you have 120VAC to control board?

Pretty rare for an ac to not show some signs of life, fan turning slowly, or running only with spin start etc. Sounds like a control issue board most likely, or 120V supply.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #6 – October 19, 2018, 08:59:59 am

Will try to follow the power path later today. Got stuff to do this morning.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #7 – October 19, 2018, 10:52:24 am

Ours has a 12v blade fuse on top under the cover for the controller

Re: Roof A/C not running - replaced capacitors - what next?

Reply #8 – October 19, 2018, 10:54:20 am

Checked that blade fuse. Appears to be good.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #9 – October 19, 2018, 11:04:03 am

check power going in and out of switch first

Re: Roof A/C not running - replaced capacitors - what next?

Reply #10 – October 19, 2018, 12:53:09 pm

Neither fan or compressor start. Taking up DVM now.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #11 – October 19, 2018, 01:41:26 pm

Called Dometic and spoke with tech support. They advised to replace the board and if still not functioning, replace the unit.

Guess I'll get new board.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #12 – October 19, 2018, 02:10:46 pm

Scott,

But you HAVE confirmed 120 VAC to the board?

12 VDC signal from thermostat?

Re: Roof A/C not running - replaced capacitors - what next?

Reply #13 – October 19, 2018, 02:13:23 pm

No I have not but will before I order new board.

Thanx for your input.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #14 – October 19, 2018, 02:14:30 pm

where is coach now ? I will be at wolf creek park this weekend I can look at it for you I work on them rooftops.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #15 – October 19, 2018, 02:16:17 pm

We are in Magnolia, TX. Great offer but you appear to be quite away.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #16 – October 19, 2018, 02:31:28 pm

Is it worth the effort to switch out boards between your units? If the problem follows the board, you know you need to order a new one. If it doesn't, keep troubleshooting.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #17 – October 19, 2018, 02:38:15 pm

Good thinking. Might give that a try. 👍

Re: Roof A/C not running - replaced capacitors - what next?

Reply #18 – October 19, 2018, 03:06:06 pm

well if you have troubles let me know I live in conroe/woodlands just taking my MH to the lake this weekend for a car show

Re: Roof A/C not running - replaced capacitors - what next?

Reply #19 – October 19, 2018, 03:08:59 pm

We will be on Lake Conroe also starting Sunday afternoon @ 1000 Trails.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #20 – October 19, 2018, 03:14:16 pm

I don't know, but if they make one, I'd buy a 'Dinosaur' board. If it's not the board, it's always good to have a spare!

Re: Roof A/C not running - replaced capacitors - what next?

Reply #21 – October 19, 2018, 03:41:46 pm

There may be jumpers or dip switches that tell the thermostat which board to talk to for Zone 1, Zone 2 etc. You might also experiment with switching those or reversing the wiring to rule out a dead zone on the thermostat.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #22 – October 19, 2018, 08:18:24 pm

Mine had a wiring diagram on the inside of it. That was key to finding that the terminals in one of the connectors to the board was not making good contact.

Re: Roof A/C not running - replaced capacitors - what next?

Reply #23 – October 19, 2018, 08:47:07 pm

Thanks all. Will try to get up there tomorrow. Today did not turn out like I expected. 😊

Re: Roof A/C not running - replaced capacitors - what next?

Reply #24 – October 20, 2018, 10:41:18 am

Energized the unit from the thermostat.

Disconnected and reconnected com. cables above the white interior vent cover. Tried to touch contacts in the male comm connector and saw no life.

How do I verify signal from the t-stat?

Was able to verify 121 vac into control board.

Saw nothing coming out.

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