Questions about Coleman Mach basement a/c

[John Stephens]

I have a 2005 Adventurer 38J with the original a/c and heat pump. Lately, whenever I turn on the a/c, it shoots the amp reading up to the 40-60 amp range for a second, and then drops back to the normal 13-15 amp range until the second compressor kicks on. Does this mean the start capacitor for the #1 compressor is going bad? If so, how can I tell which capacitor is which when I pull the cover off the unit?

As an alternative, would it be better to simply replace both start capacitors, assuming if one is going bad, the other will quickly follow?

Or, while I'm there, should I replace the run capacitors as well since this unit is 19 years old, and to my knowledge, none of the capacitors have ever been replaced?

I know nothing about this subject other than knowing the capacitors have to be discharged before playing with them. So any advice or help you can provide will be appreciated.

 

[Ray-IN]

Lets begin with the model# of your ColemanMach/RVP basement unit. You'll find the model # on the left end of the cabinet (as looking at it). Remove the 3 screws on the right end of the body panel grill by opening the adjoining door to see the screws. Then there is another underneath, it is obvious.
Now you can use a mirror to see in the tight space on the left end and read the model#, which is likely 6535-xxx.
The electrical box contains the start/run caps for both compressors and the IDFM=indoor fan motor. The ODFM=outdoorfan motor cap is inside the cabinet attached to the blower housing.
This is the 6535 service manual. It has an excellent troubleshooting guide.

You said comp.#1 startup causes a huge amp spike, yes that is too high. To test the compressors requires switching the 12V signal wiring to both relays so #2 compressor becomes #1 compressor and always starts first. Then when you start the unit and observe starting amp-draw, the huge spike should now be #2 compressor.
New compressors are available if required, in fact everything but the OEM cabinet is still available online. RVP sells a new replacement unit if it's needed.
This is a detailed write-up of how to remove and service the basement unit, by Bill Elsenpeter/Duner on irv2.com. PROCEDURE FOR SERVICING BASEMENT A/C …PROCEDURE FOR SERVICING BASEMENT A/C UNITS ON WINNEBAGO PRODUCTS By Bill Elsenpeter July 8, 2008 “Duner” on IRV2.com Revised Aug 20, 2013 - [PDF Document] Instead of using buckets and a board for a table, I rented a hydraulic table, so I didn't require a helper.
Feel free to ask questions as they arise.
Yes, replace all caps with identical specs, old ones do weaken through the years
added: If you prefer to hire this work done this is the best place: Shelburne RV Service They even have a utube video of servicing an RVP basement unit.

 

[John Stephens]

I misspoke when I gave the impression that this spike occurs every time I turn the a/c on. It did it once last year while we were on a trip in August. We put the coach in storage in September and I visit it frequently to do other work on it throughout the winter months. I run the generator every two weeks religiously to exercise it and keep the coach batteries charged. To provide a half load for the generator, I turn on the a/c. Two times in storage, it has spiked, with the last time occurring the day before yesterday when it reached 53 amp. Yesterday when I went out to work on it, I turned on the a/c and the amp meter rose to only 23 amps, where it should be. This inconsistency is what is making me think the start caps are going bad.

But from the way you describe your solution, it sounds as though you think the #1 compressor is going bad. Is that true? I appreciate you indicating that all parts are still available because the mechanics down here in SW Florida have indicated the opposite. They also have said it is nearly impossible to find a replacement unit for this a/c, and if you can find one, it will cost over $6,000 plus labor to install it.

Since I am 71 with a bad back, it will be impossible for me to pull the unit to work on it, even if I knew what I was doing. Your suggestion to use Shelburne RV Service is noted and appreciated. If I need someone to work on it, they won't be that far out of my way during my next trip which will take me up I-75 to I-24. Cleveland is just a little further up 75. I have no mechanics here in SW Florida that I either trust or can afford, having just lost my house mechanic when he went out of business. I try to do as much work as I can and know I would be able to change out the caps. But replacing a compressor will be beyond my abilities.

When I return to the coach tomorrow, I'll check the model number. In the past, I have had my mechanic replace the inside and outside fan motors and thoroughly clean the entire unit since we have three hairy dogs who travel with us. However, I know the compressors are still original. I was hoping to have the a/c last another two years before needing major work because that is how long I plan to keep the coach.

 

[Kirk]

Or, while I'm there, should I replace the run capacitors as well since this unit is 19 years old, and to my knowledge, none of the capacitors have ever been replaced?

Am I correct in assuming that you bought it new and so know the entire history?

I try to do as much work as I can and know I would be able to change out the caps. But replacing a compressor will be beyond my abilities.

While I have a lot of RV experience and have worked on a lot of different RVs and RV systems, I have no experience on the basement air conditioning systems. What I can tell you is that capacitors are not expensive and with a unit that age it can't hurt to replace them all. I would try the start capacitors first and then monitor to see if that helps. While it could be a compressor problem, to me it sounds more like a start capacitor since it only shows the problem when the compressor is starting. That is based on my experience with electric motors in other types of equipment. It is possible that the compressor is failing but I would do what you can do easily first. If you have not worked with capacitors before, be very careful as even experienced technicians get bit at times and also make sure that you get the proper replacements.

 

[John Stephens]

Am I correct in assuming that you bought it new and so know the entire history?

While I have a lot of RV experience and have worked on a lot of different RVs and RV systems, I have no experience on the basement air conditioning systems. What I can tell you is that capacitors are not expensive and with a unit that age it can't hurt to replace them all. I would try the start capacitors first and then monitor to see if that helps. While it could be a compressor problem, to me it sounds more like a start capacitor since it only shows the problem when the compressor is starting. That is based on my experience with electric motors in other types of equipment. It is possible that the compressor is failing but I would do what you can do easily first. If you have not worked with capacitors before, be very careful as even experienced technicians get bit at times and also make sure that you get the proper replacements.

Kirk:

I bought the coach in 2015 when it was 10 years old. The original owner never used the generator (69 hours after 10 years), never used the a/c, and only had 23,000 miles on the coach. When I had the a/c serviced the first time, it was because the ductwork inside the back cap of the coach had separated. That told me the original owner never used the system or he would have known there was something wrong and probably had it repaired. The second time I had it serviced was when the inside and outside fan motors went bad, and that mechanic told me all parts and electronics appeared original, and to expect the caps and compressors to go bad over time. Unfortunately, I got no service records from the original owner or the dealer who sold it to me, so I do not know the entire history of the coach and can only assume certain things. That's why I spent a small fortune on it after buying it to make sure everything was properly serviced. At this point, I almost have a new coach with an old body and chassis that I try to keep up as best I can. We have put over 50,000 miles on it in the past nine years and plan to run it for another two or three years. In 2021, we got caught in a 60 mph crosswind that blew part of the roof off in Washington state. Before we could get home to Florida, we ran through two severe storms that caused leaking inside the ceiling of the coach. Our insurance company couldn't find anyone who could restore the entire roof from top to bottom, so they totaled the coach. I bought it back and had RV Flex Armor put on the roof, and sprayed bleach water on the water spots on the ceiling to get rid of most of them, and now, the coach is in excellent shape for a 19-year-old vehicle.

While I have not changed out caps before, I know how to discharge them before working on them and know to replace them with the proper range of charge. Your thoughts are the same as mine - since the a/c runs very well, and the startup is the only time an issue appears, it seems the start caps are the culprit. I haven't had any known issues when the #2 compressor starts, but it also seems logical that if one cap is going bad, the other won't be far behind, so I might as well replace both of them while I'm in there.

Thanks for the response.

 

[Ray-IN]

FYI; this is the RVP/ColemanMach 6535 parts list. If it turns out that is your model.
Replacing the start and run caps is easy, just discharge the existing caps, remove the wiring and replace with the same specs as the original. Any electric supply house will have them.
The start caps are hard-start style, replace with the same type. Some have bought an installed soft-start caps, but IMO is a waste of money.

 

[John Stephens]

Everyone, thanks for all the replies. I replaced both start caps for the compressors and a third for the fan. The top of it was mushrooming, so I assumed it didn't have much longer. Upon putting it back together, I started the a/c, and it did what it was supposed to - jumped to 23A and then immediately dropped down to 13A. The run caps appeared to still be in good shape, and the compressors run fine at this time, so I'll delay replacing them.

The total cost of this was $26 for all three caps. Had I taken this to a local dealer's repair facility, they would have wanted over $600.

I saved another $1,265 by cleaning out my Splendide w/d combo that wasn't heating the dryer. In talking to LaMesa RV, they said they would charge a $150 diagnosis fee, plus $250/hr labor. It took me three hours to remove the appliance, take it apart, call Splendide to determine the problem, find the clog and remove it, put the unit back together and move it back in place, and then spend an hour cleaning it out by running four cleaning cycles. They would have charged me for four hours labor, the diagnostic fee, a 3% shop materials fee, and tax. You can buy a new unit for nearly the same price.

There are some things I can't do with the coach due to age and physical limitations, such as pulling the a/c unit out to clean it, or due to lack of experience, such as removing the jacks and hydraulic cylinders for the slideouts that need rebuilding. But I'm getting tired of getting ripped off by the RV mechanics in this area who charge double what the labor costs should be compared to other mechanics and then tack on extraneous fees only because they can, not because they are out the money. And then provide only a 90-day warranty on the work they did. Anything I can figure out how to do myself will get done by me.

The last time I needed a generator tuneup, I took the coach to the Cummins Onan dealer in Fort Myers. I told them I had already changed the oil and filter, air and gas filters, and only needed them to change the spark plugs. They hit me with a $1250 bill to install all new filters, oil, new plugs, and a new carburetor. I refused to pay for the new oil and filters since I had told them I had just changed them. They lowered the bill to $1,175. I needed another tuneup last month, so I bought a new u-joint for my socket set and did it myself. Total cost - $56 for all the parts.

 

[Kirk]

Anything I can figure out how to do myself will get done by me.

Most of us find that to be best for the budget. Another positive thing is that I have found that many (if not most) RV techs do not have very good understanding of electrical principles and sometimes other things that they should know. The result is that very often troubleshooting is done by swapping parts until they find something that works. On top of that, it is now uncommon for shops to pay their techs a commission on parts used to encourage it. I have found that in most cases you will get better service from a company that services RVs but does not sell them.

 

[Ray-IN]

John Stevens, the run cap for the outdoor fan motor/ODFM is mounted on top of the fan housing and can only be replaced by removing the unit from the MH, then removing the sheet metal top.
If that is necessary, IMO it's less money in the long run to completely service everything inside the cabinet. The fan shaft bushings require oiling via the oil points, same thing for both the ODFM and indoor fan motor/IDFM motors.
I extended the leads for the ODFM cap so I could place it inside the electrical box with the other 5 caps.
BTW, the basement units weigh 200#, JIC you are considering removing it yourself. I rented a hydraulic table, so no lifting involved, just pulling and tugging.