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Coleman Mach Model 6736C917 anyone top one off?

NickD on Sat June 27, 2009 7:24 AM User is offline

Year: 1982
Make:
Country of Origin: United States

RV Rooftop AC, 120 VAC, cleaned it up yesterday, evaporator, condenser, fan, redid all the electrical, get a real good air blast, but not cold enough. It will cool the motorhome down to 70*F from 93, but takes about four hours. Can't even recall the brand of last one I had, but recall it cooling it down from 90 to 55 in less than two hours.

Evaporator feel colds on the sides, but just cool where the fan blast on it and the condenser feels warm instead of hot. Really isn't much worse than when I got it 3 years ago, was hoping by cleaning all the dust out of the condenser and evaporator and redoing the electrical, kind of corroded, it would do better.

Difficult to find anything on this old model, but assume it's a 12,500 BTU unit, just about all of them are. What I don't like about this thing, using just one motor for both the condenser and evaporator fan, so only has one speed. Using a damper to control the air flow, but I did install a motor control to quiet it a bit, doesn't bother me, but keeps the wife awake.

Feel it's low on charge, can't even find a label on the darn thing, but has got to be R-22, but I never recharged one of these things, anybody here ever do that?

Ha, wife tells me two weeks ago, would like to go camping over the fourth, every damned campground is booked solid, should have done that last year. Was always lucky, always found a spot by just driving in, but she feels insecure, so we decided to hit Milwaukee instead. Was there last year, city was practically deserted and hit that Summer Fest music show she liked. Can park it in the Veterans Park right on the lake front, but have to leave at 10:00 PM where we can plug in at my son's home and he won't even charge me the 40 bucks per night they are charging now.

Can also avoid the traffic when coming back, typically the back up on I-90/94 is 20-30 miles if headed south, but not a vehicle on the road headed north. Not like it was even 30 years ago, any campground back then, we had all to ourselves and the fee was a buck, must have been smoking crack when we purchased this thing, forgot how crowded this place has become. But is nice to have when moving our daughter to the dorm, makes a nice moving van.

bohica2xo on Sun June 28, 2009 2:44 AM User is offline

Nick:

Contact the folks that actually made the unit

RV Comfort Inc.

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Sun June 28, 2009 7:13 AM User is offline

Already did download a replaceable parts list and the service manual for this thing when I first got it. Manual is mostly on electrical testing, feel that I am lightyears ahead of them on this subject. They do list these tools besides a hammer that I already seem to have laying around someplace.

1. Ammeter
2. Ohm Meter
3. Volt Meter
4. Refrigerant Recovery Equipment
5. Charging Cylinder
6. Vacuum Pump
7. Vacuum Gauge
8. Leak Detector
9. Brazing Equipment
10. Gauge Manifold

But seem to be having a problem attaching my gauges to a crimped and welded suction tube. And should have used my microscope to find the refrigerant type and capacity.

Kind of striking out in finding the adapter fittings that need to be brazed so you can attach your refrigerant equipment. If my compressor is worn, might as well add about ten bucks to what they want for it, and buy a brand new unit. Think I will look around, RV dealers around here, tons of them are really hurting right now.

jglanham on Sun June 28, 2009 12:37 PM User is offline

Nick, What you might try is a line tap valve with a hose fitting. It is like a saddle tap for a water line. Johnstone Supply stocks them. On their online catalog, go to the product index and look for access fittings/valves, then line taps. I used one many years ago to repair a window unit. It never leaked. It eliminates the need for brazing. Just a suggestion. Hope it helps.

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johnl

NickD on Sun June 28, 2009 2:28 PM User is offline

Is this what your are talking about?



Looks pretty neat, no refrigerant loss I assume, but gives means to check pressures and perhaps add a tad of R-22 if it needs it. Thanks for the tip.

jglanham on Sun June 28, 2009 3:59 PM User is offline

That's the one! It shouldn't leak if installed on the low pressure side. However, since it is a sealed system, and you are having to add refrigerant, there must be a pinhole leak somewhere. But then, you already know that! Let us know how it works out.

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johnl

NickD on Sun June 28, 2009 10:51 PM User is offline

Took at step back and did the performance check first, manual states after running the AC for a half an hour to measure the inlet and outlet temperatures where the outlet should be 18-22*F less than the input. Measured 75*F in and 52*F out, so the unit is doing what it is suppose to be doing.

When I was cleaning and rewiring the unit, on the red hot roof, the sun was directly overhead and I think it fried my brain. Was also beating down in that 3 by 9 foot windshield giving very good reason for a long cool down. With the sun beneath the trees, it did cool down from 83 to 65*F in under an hour, just have to park it in the shade.

TRB on Mon June 29, 2009 12:26 AM User is offlineView users profile

Quote
Originally posted by: NickD
Is this what your are talking about?







Looks pretty neat, no refrigerant loss I assume, but gives means to check pressures and perhaps add a tad of R-22 if it needs it. Thanks for the tip.

I've used these before and it works fine w/o leaks.



-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

NickD on Mon June 29, 2009 7:20 AM User is offline

This thing does have provisions for two AC's, if I move down south, looks like I should add the second one.

We actually had three days of 90 degree weather, but it rained most of Saturday and was too cool Sunday to go to the lake, wife and daughter love the beach. Wonder what kind of weather we are going to have over the 4th? Can't ever believe the forecasts.

NickD on Mon June 29, 2009 11:09 AM User is offline

In hearing the weather report this morning, all I have to do to cool my motorhome tonight to 40*F is to open a window, crazy weather.

TRB on Mon June 29, 2009 1:37 PM User is offlineView users profile

We finally got some nice weather here this past weekend. But it is cooling down again to 105 today.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

JJM on Tue June 30, 2009 8:37 PM User is offline

But will they leak if installed on the high side? Really need pressure readings on both sides to top off, unless you're evacuating and charging to spec.

I always wondered how they manage to do it at the factory... no service ports, just a line that's crimped off then soldered/brazed. How do they prevent the refrigerant from leaking out during the process? A simple crimp alone can't do it. There has to be some kind of rubber jacket that does the initial sealing during the crimp, and then the end can be soldered/brazed.

Joe

NickD on Wed July 01, 2009 6:07 AM User is offline

Watched that on How it's Made, this guy shoves like a rubber nipple on the open line, it draws a vacuum and dispenses the charge, can tell you, they don't draw a vacuum for three hours and take a nap, more like two seconds.

Then they use This tool to seal and cut the line off while still connected to that vacuum charge dispenser.

They were making room air conditioners, how would you like to do that eight hours a day? I only lasted 6 weeks on a production line making speakers, was fun for about the first ten minutes, then each day was like an eternity making going to college a lot easier. Wonder if those guys or gals get carpal tunnel?

mk378 on Thu July 02, 2009 11:52 AM User is offline

Copper tubing can be crimped off absolutely airtight. This is done to evacuate and seal ceramic/metal electron tubes such as microwave oven magnetrons and large radio and TV transmitter tubes. If you keep crimping between two hard round cylinders until the tube is actually pinched in two, the feather edge at the end is actually cold-welded together. I don't know if a crimp alone can withstand pressure though. The old technique on refrigerators and A/C was to crimp partway then fill the open end after the crimp with braze.

The clamp on service fitting shown above will work, there is a slightly better type that has a separate screw to operate the piercing needle and valve. After recovering the refrigerant through one of those fittings, it is possible to remove the crimp tube and braze on a regular service fitting instead.

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