Coleman Mach Basement Air Unit Capacitor Repair

[AKIQPilot]

For reference, my unit is a Coleman Mach 6535 Series, Two Ton Basement Air Unit.

So now that summer is basically over everywhere except the deep south.........

Compressor 2 on my Basement Air unit quit running last week. It's still nearly 100f every day in the Las Vegas area and one compressor was struggling to keep up. I was surprised by its performance but the direct sun and near 100f temps were really taxing the single air conditioner.

I confirmed it was Compressor 2 by looking at the amperage draw on my Surge Protector. With everything off except the air conditioner I was seeing 0-1 amps of load on Line 1 and about 14 amps on Line 2. The TStat was set plenty low enough to trigger Compressor 2.

I called about 4 local Mobile Mechanics and one local residential AC guy. 3 mechanics told me they don't work on the Basement Air Units. The Residential guy told me he didn't work on Motorhome AC units, even after I explained to him how it was similar to a Resi unit. The last mobile mechanic told me he was booked up for a week and that repair costs would like start at $350 and go up from there.

A non functioning Air Conditioner was something I had worried about for some time so I had read through several threads over the years. I can't say I knew what I was reading but I knew there were a few threads out there that discussed troubleshooting and common problems. Yesterday I found and downloaded the Coleman Mach Service manual for the 6535 Series unit. There is a service manual available for the 6536 Series unit on line as well. While I am not an electrician I do know how to use a multimeter and I do a fair job of reading electrical schematics.

Of course from all of the reading I had done prior I was leaning (hoping) it was a Start or Run Capacitor for the #2 compressor. I woke up yesterday morning and called two big RV dealerships here in Las Vegas and both of them had the Start Capacitor Kits in stock. Neither stocked the Run Capacitors. I checked with a local appliance parts store here and they had the Run Capacitors in stock but don't carry the Start Capacitors. So I'm thinking maybe I should replace the Start Capacitor first since it's a stocked item at the RV store.

I then began reading through the service manual to try and eliminate other reasons for the #2 comp not to fire. I confirmed that the TStat was sending 12vdc to to the control board in the unit for both compressors. I confirmed there was 120vac to all places in the unit where it was supposed to be. By noon it was getting too hot to shut down the only functioning AC unit I had so I just went to the parts store and bought the Start Capacitor Kit and kept reading.

Hard Start Capacitor Kit Part # 8333A9021 was $32+tax. This kit is put together by AIRXCEL out of Kansas. The kit has the capacitor, the motor starter, new wires, installation bracket and instructions. It says it's for the Coleman Mach Roof Air units but the part number cross referenced over to the Hard Start Cap I have on my basement unit.

The Run Capacitor is Part # 1499-5671. Locally this part was $29+tax. I didn't buy the Run Cap but they carry them locally. I will very likely pick up another Hard Start kit and a Run Cap to have on hand for the next time I find myself with less than adequate air.

So this morning at about 7am It's a nice cool 71f outside and I figured it was a perfect time to shut down all power to the unit and swap out the Hard Start Cap on Comp 2. So I shut down all power, AC and DC. Opened up the side panel. Unplugged and unmounted the #2 Start Cap and plugged in the new one. I used the same yellow wire from the original Start Cap but used the new red wire that came in the kit. The Start Cap took about 5 minutes to install.

I restored power to the coach and turned on the AC with a setpoint 1* lower than room temp. #1 Compressor started right up and began blowing cold air drawing about 14amps. While outside I had my wife lower the setpoint to about 4* lower than room temp. A few seconds later Compressor #2 started up and began drawing about 9amps. I let both compressors run for a few minutes and before long it was 67f inside the coach. I put the setpoint back up to 72 and here we sit with an AC system that seems to be functioning normal again.

I just wanted to log what I found and how I went about troubleshooting my Basement Air problems. Not every challenge is going to be this easy but anytime I can save $300+ on a simple repair I will sure give it a try.

Hope this helps someone in the future.

Coleman Mach 6535 Service Manual

[vsheetz]

Great job. Thanks for sharing.

[AKIQPilot]

I didnt take many pictures but here are a few.

My original Hard Start Capacitor.


The Run Capacitors in place. #1 on the left #2 on the right.


Hard Start Caps and Motor Starter

[FIRE UP]

Tom,
OUTSTANDING WRITE UP!
Without a doubt, very easy to follow. I have a question or two for you.

1. I'm fairly competent with a VOM so, could you show/tell/explain to me how you confirmed you got 12V to the needed spots for A/C operation?

2. Could you do the same for the 120VAC?

In other words, where did you put your leads for confirmation of the 12VDC to check where 12V was needed? And, the same on the 120VAC? I have a buddy that just picked up an '05 39' Journey with the 350 CAT and, he's maybe having a bit of the same exact issue with his basement A/C. When we visited him right after he purchased it, he'd had the A/C on for quite a while and, it really wasn't very cool in there with the outside temp of about maybe 80 degrees. And, I'm not that savvy on what the "One place" should read when certain conditions are present.
Scott

[AKIQPilot]

Originally Posted by FIRE UP

Tom,
OUTSTANDING WRITE UP!
Without a doubt, very easy to follow. I have a question or two for you.

1. I'm fairly competent with a VOM so, could you show/tell/explain to me how you confirmed you got 12V to the needed spots for A/C operation?

2. Could you do the same for the 120VAC?

In other words, where did you put your leads for confirmation of the 12VDC to check where 12V was needed? And, the same on the 120VAC? I have a buddy that just picked up an '05 39' Journey with the 350 CAT and, he's maybe having a bit of the same exact issue with his basement A/C. When we visited him right after he purchased it, he'd had the A/C on for quite a while and, it really wasn't very cool in there with the outside temp of about maybe 80 degrees. And, I'm not that savvy on what the "One place" should read when certain conditions are present.
Scott

Glad to, let me see if I can help.

First confirm the TStat is sending the proper signal to the control board on the AC Unit.

In the service manual near the bottom of page 8 is a basic diagram of the thermostat wiring. You will see (Y1) Yellow wire is for Compressor 1. And (Y2) Orange Wire is for Compressor 2. You will also see (B) Blue wire is 12VDC Negative. There are two blue wires in the TStat. One is solid blue and one is blue with a white stripe. I believe they are both 12VDC Negative because I got the same readings regardless of which blue wire I used as the negative. The drawing on page 8 shows the plug at the electronic control board on the unit. That plug can be seen in the middle of the control board with all those same colored wires coming from the Tstat.

On Page 19 of the manual you have the truth/troubleshooting table for Compressor #1 Checkout Cooling Mode. In the second box down on the left of the table you see [12VDC to Y1 and B at Thermostat, (remember time delays)]. Make sure the AC is on and the tstat is set to 1* below room temp. Now take your volt meter and check for 12vdc at the TStat between the Yellow and the Blue wires. You can also perform the same check at the 9 pronged plug on the control board on the unit if you suspect a wiring problem between the TStat and the control board.

On Page 20 you have basically the same truth/troubleshooting table for Compressor #2. In the third box down it says to check for [12VDC at Y2 and B at thermostat] So now you need to lower the setpoint a few degrees to get the trigger for the second AC unit. I lowered mine about 4 degrees and tested for 12VDC at Y2 Orange and B Blue.

Next it says to check Compressor Run Relay for proper operation. That was a little vague. I tested 12VDC and 120VAC at the relay and both Comp 1 and Comp 2 relays. Both seemed to read the same voltages so I assumed both were functioning properly.

On page 19 and 20 the next step is to [Check Comp Start Device, Check Comp Run Capacitor, Check Compressor motor Windings for Open Ground]

I was a little apprehensive sticking my VOM onto a capacitor so at this point I decided I would just buy a new Hard Start Kit and install it on Comp 2.

So at this point I decided to start by replacing the Hard Start Cap first because it was an item that was stocked at both big RV dealers in Vegas and it was available from Campers World which I typically only use as a resource. The Run Caps were not stocked at any of the RV dealers so that told me it was less likely to be the issue.

I also checked 120VAC at the unit by testing the wires coming in to the unit below the capacitors and control board. I turned off the power at the breakers, verified 0VAC on both circuits. I turned Comp 1 breaker on and verified 120VAC at the unit. I then turned on Comp 2 breaker and verified 120VAC at the unit.



So that is the basics of how I troubleshot the TStat and Relays on my unit. the Coleman Mach 6536 unit may be slightly different so you may have to download the service manual for that unit if your buddy has that basement air unit instead of the 6535 like I have.

[Unicorn Driver]

Thats a great job Mike.

[Greatscot]

Here is a video by the guy that not only replaced my roof but repaired the basement ac as well.

https://www.youtube.com/watch?v=dTq7LuWHihU

As he says in the video, I was told my #2 compressor was bad. Turns out it wasn't. This power board (looks like a circuit board to me) wasn't cheap. About $183. I'm guessing a lot cheaper than trying to find a new compressor.

Thanks for the information about the capacitors. And the manual

[AKIQPilot]

Originally Posted by Greatscot

Here is a video by the guy that not only replaced my roof but repaired the basement ac as well.

As he says in the video, I was told my #2 compressor was bad. Turns out it wasn't. This power board (looks like a circuit board to me) wasn't cheap. About $183. I'm guessing a lot cheaper than trying to find a new compressor.

Thanks for the information about the capacitors. And the manual

Haha. I watched that video early on in my research this week. That guy is an RV Repair God IMO. When he just started unplugging wires and tossing them aside I knew it was way over my pay grade. I did watch it all though and it made me a little more comfortable to try and tackle my problem.

If the Start and Run Caps wouldn't have fixed my problems I would have gone for an upgraded control board. Local dealer here in Vegas has them for $167 so I know it was an option if one or more Caps didn't get me back on track.

That is the kind of guy we need access to around this forum. He obviously knows quite a bit about RV's. I need to watch more of his videos.

Thanks for posting.

[AKIQPilot]

So a quick update on my AC's performance today.

*It was +102F where I am and my nearly black Moho was in direct sunlight all day.
*I have my TStat set at 73.
*The #2 Compressor kicked on around 9am and never shut off all day.
*Inside my upper front cabinets showed 133f on the inside walls under direct sunlight.
*Inside temp of my interior walls showed 106f under direct sunlight.
*Inside room temp got to a high of 77f today.
*Inside room temp was 89f in the same conditions yesterday.
*Air temp from ceiling ducts in living room showed about 52f. 25* less than room temp.
* Air temp from rear most ducts closest to AC unit showed 45f. 32* less than room temp.
* Sun went behind the neighboring building about 40 minutes ago. No more direct sun on the side on my coach.
* As of this minute the temp inside my coach is down to 74f.
* By 7pm the Tstat will be satisfied and the AC will shut down and begin cycling on 1 Compressor.
* Every day this week before today the TStat was never satisfied before 9pm.

My AC is definitely working 100% better than it was yesterday and all the last week.

[Ray,IN]

Tom, you might find this interesting: replacing the Coleman-Mach thermostat with an Ecobee.
The website is down tonight, don't know when/if it will be operational again.
This thread is also helpful: http://www.thermostatforums.com/show...12-VDC-control)

[AKIQPilot]

Wow Ray. An Ecobee would be awesome. I have Ecobee stats in my home in AK. They work fantastic.

[billyb]

Also really great great post. I bought a 9 year old unit last year and I like to know all I can about the ac and the 1200 fridge.bill

[Unicorn Driver]

I spoke to Ecobee about this and it needs Internet to work remotely. It will not work over just wireless.

[Greatscot]

I agree about James, RV Expert is the name of his shop. He also installed a Grade Brake on my Allison 1000 since my MH is a 2004 and Allison didn't include the grade brake until 2005.