Duo-Therm A/C Clicking - Will not turn on

[hdougj]

Hello,

I have a roof mounted A/C with wall mounted thermostat. It is a Dometic Duo-Therm unit. When I flip the thermostat to A/C, I can hear it click in the A/C but nothing happens. I can get the furnace to click on from the thermostat which leads me to believe it is something wrong with the A/C it self.

I have taken the cover off of the A/C unit and the fuse is good. Just when I flip the thermostat to A/C it clicks and nothing happens.

Anyone have any insight or familiar with these units?

[dougrainer]

hdougj wrote:

dougrainer wrote:
From his description of the problem----HE HAS NO 120 POWER TO THE AC UNIT. If he had 120 power to the unit and the roof top control board clicks, then even IF he had a capacitor problem, BOTH the Fan and Compressor CAPs would not have failed. Either the Fan comes on or the compressor. Since neither does, he has no 120 power to the top unit. Doug

Just a quick update. I went up there and visually inspected the capacitors. They both looked great. Took a multimeter up there and had no power going to any of the wires. I have a completely different fuse panel for just my A/C that I never knew about. It is not part of the regular panel which explains why I never noticed it wasn't flipped. Thank you for all of your help.

This points to a problem with forums. Rarely do the respondents READ and understand the complaint in its complete reading. For novices asking for help, off the wall repairs are rarely needed. KISS, is the BEST answer to most complaints. CHECK the easy simple things first. Part of my job, is talking to the customer and getting a full response on his complaints. THAT helps me zero in on the actual problem. NOT waste time doing off the wall check outs and tests. Which saves the customer money. Doug

[hdougj]

dougrainer wrote:
From his description of the problem----HE HAS NO 120 POWER TO THE AC UNIT. If he had 120 power to the unit and the roof top control board clicks, then even IF he had a capacitor problem, BOTH the Fan and Compressor CAPs would not have failed. Either the Fan comes on or the compressor. Since neither does, he has no 120 power to the top unit. Doug

Just a quick update. I went up there and visually inspected the capacitors. They both looked great. Took a multimeter up there and had no power going to any of the wires. I have a completely different fuse panel for just my A/C that I never knew about. It is not part of the regular panel which explains why I never noticed it wasn't flipped. Thank you for all of your help.

[dougrainer]

From his description of the problem----HE HAS NO 120 POWER TO THE AC UNIT. If he had 120 power to the unit and the roof top control board clicks, then even IF he had a capacitor problem, BOTH the Fan and Compressor CAPs would not have failed. Either the Fan comes on or the compressor. Since neither does, he has no 120 power to the top unit. Doug

[Ivylog]

Here is a recent post with more info on this subject. It's a common problem and the capacitor can still LOOK good but is not. For less than $20 it's worth having a spare one. Easy fix after you short the contacts with a screwdriver before removing.

[Golden_HVAC]

Google 'bad capacitor picture' and you might see what one will look like when 'popped'.

You can buy a $39 amp meter that clamps over one AC power wire, and will tell you the amperage going through it from Lowes Hardware.

You can also buy the $89 model that will also measure DC amperage by clamping over one wire. So it measures AC or DC amperage, just clamp it over the wire.

Both have a 'capacitance' checker, and you could remove both wires from the capacitor (with power unplugged from the RV) and test it. If it reads 35 Mfd,or whatever the capacitor is rated at, then it is good. I have replaced a LOT of bad capacitors, including one on my sister's A/C unit at her home.

With the system set to AC amps, and one wire to the compressor in the jaws, then have someone turn on the unit from below. If the capacitor was good, and the amperage is over 5 amps for a few seconds, but the compressor still does not come on, you probably have a bad compressor. You can confirm this by ohms to ground. Anything over 7,000,000 or 7.0Mohm, you will be OK. Something less, and you are likely to need a new compressor.

Considering it would take me 4 - 6 hours to install a compressor, and cost me at least $400, and that I can only warranty the replacement compressor for about 30 days labor or 90 days parts, you might as well spend $750 and get a new unit with full warranty!

Fred.

[hdougj]

Thank you for all of the fast input. I will head up there in the morning and report back with what I find

[lj2654]

My start capacitor was the problem with mine when it did what yours is doing. I took the cover off the roof a/c and checked the start capacitor. Mine had a terminal broken off the end.

[hdougj]

I'm hooked up to a 50 amp.

[downtheroad]

What kind of power are you hooked up to...?
Are in in an RV park with 30a or hopefully 50a power or are you plugged in at home to a garage outlet?

[Executive45]

Sounds like the start capacitor is bad. About a $20 fix. Use caution removing the capacitor as they "hold" a charge, even with the power OFF. Use an insulated screwdriver to ground two of the posts before handling. Easy fix but use caution...make sure power is OFF to the A/C unit as well...good luck...Dennis

[Teacher_s_Pet]

Haven't had a Duo-Therm for years, but is there a black canister (starting capacitor) about 4" long with 4 spade connections? If so look at the 1/4"-5/16" hole close to the spade connections that has what looks like wax paper inside it. If it shows evidence of the paper bursting, the capacitor is bad and will need to be replaced.