trailmug

Agree, sounds like it cycling off due to the evaporator frost sensor. When's the last time you cleaned the return filters? Could be a dirty evap (probably most likely) or low charge (probably less likely); least likely of all could be the evap frost sensor is bad. Try running it with the fan manually on hi. If it runs longer, I'd suspect a dirty evap.

I don't mean to be argumentative, but the main breaker's label says CAT NO: TB250 which would make it a Thomas & Betts breaker. Square D would be QO or HOM in this form factor.

I would be interested to know if the breakers are makes/models that are listed for the load center. A lot of stab-on breakers will "fit" without being intended for a use with a particular panel, and improper application is fairly common. I expect the fishy smell is the ABS out-gassing. The one I can read appears to be a TB series.

Looks like the evap fits up against a drip rail that is supposed to keep it from dripping into the recirc, and the water just runs down the cover to the hose fitting at the bottom? Yuck.

Out of curiosity, did anybody replace/remount that receiver/dryer? I've never seen one mounted horizontally like that. Seems like it'd have to be half full before it'd flow any liquid out of the pickup tube. Image attached for detail. Also, there's a pressure switch attached to the top of it that doesn't seem to be connected to anything. I presume that's a binary switch which has been jumpered. It's responsible for preventing the system from starting if you lose your refrigerant charge, and kicking the compressor off if the pressure gets too high.

I'm getting potentially wordy and obnoxious here, but I spent a good deal of time with the SCS system after multiple shops had failed to fix it and I found a significant amount of contamination/sludge (photos attached). I got really suspicious about the 4.0lb recommendation after reading the Sanden service manual. Factory oil charge is sufficient for up to 4lbs R134a, with more oil recommended for systems with longer lines which require more refrigerant.. I can't imagine longer lines than on a bus, so did Monaco recommend 4.0lb just so they could bolt the compressor on, evacuate, charge, and be done with it? It'll last the warranty period, at least! I flowed liquid into the evacuated system and it easily took 5 lb with the system off. Aha! I knew it needed more. Finally got around to measuring subcooling at the condenser a year later and it was 18F, which is a reasonable upper bound for a critically-charged, receiverless system to have a liquid refrigerant reserve in the condenser (a receiver system doesn't need this). At low system loads it was probably costing efficiency / compressor life due to refrigerant stacking in the condenser and raising compression ratio. The receiver looks close to a pint in size (I realize a dry ounce of R134a isn't 1fl oz, but we'll say it's close enough), so I recovered a pound to get back down to 4. For academic purposes: at 4lb the condenser measured 11F subcooling with a thermocouple at the liquid output of the condenser reading less than the saturation temperature on the high side gauge (with a front-mounted condenser). I would use that to validate the charge in the future if I don't evacuate and re-weigh. Charging beyond this went to 14F at 4.5 lb and 18F at 5 lb. The gauge pressures don't move substantially within this range. In summary of this overabundance of typing, I feel like I successfully "shade tree" validated the 4.0lb charge. If you replace any components, the Sanden manual has approximate amounts of PAG oil to add for each part replaced. If anyone ends up doing a full system flush, I settled on 4 oz additional oil due to pooling in the long, hilly suction line. Thanks for reading. 🙂

My sig owners manual indicates the refrigerant quantity (4.0 lbs). I believe to determine the correct quantity, you really need to be able to measure the amount of liquid in the receiver, which is impractical in a service setting. The pressures will be in range (with low suction as Ivan mentioned) as long as there's some liquid in the system and there's enough surface area available (not flooded) in the condenser to condense gas. Mine was cooling just fine before I recovered 2.5 lb to fix a leaky hose. 4.0 lb appears to be a pretty common value with Roadmaster chassis / SCS Frigette-based systems, so it's probably a safe bet. If you go too far, the high side pressure begins to rise as the effective surface area of the condenser is reduced by being stacked up with liquid. You're at least 1 lb overfilled at that point. Edit: the 2009 Dynasty manual in the downloads section also indicates 4 lb 134a. 👍

Maybe height, since group 31s are 2+ inches taller than GC2s? GC2s are a little bit of a squeeze in both of those upper shelves. Also I believe the second set was sold as a package with the residential refrigerator, so it perhaps helped to standardize the cable lengths, etc, to add the aft set if specified. Within the same battery tech, it seems batteries of a similar physical volume have a similar capacity. Our house set lasted 4 years, and I just replaced it with another round of GC2s, because $720 for 860Ah was vastly more economical than anything else I could think of. It is a valid point, however, that with lead batteries, only about half of that capacity is actually usable if you want to avoid prematurely aging the batteries.. and if you want to be able to start the genset. 🙂 I think the latter would be helped by a larger gauge cable, though.. maybe 1/0 vs 2ga. On float charge the generator terminals drop to 9V during cranking, and the computer will abort start if it sags to 6V. As soon as I can figure out where the other end is, I will upsize it and post results. Has anybody done anything with venting the battery bays? I would think with flooded or even VRLA, you would end up with H2S in the bay eating the steel.. which maybe is why those slide trays have aged so poorly.

Group 31 x 3 is correct for our ISX600. I had hard hot starting issues. Replaced the Interstates with Optima cylindrical AGMs wanting to rule out the batteries, which was very expensive and helped marginally. I won't buy AGM next time, especially since I went to flooded on the house batteries and an AGM charge profile would electrolyzise too much water out of the GC2s. What really helped was replacing the battery bay positive cable. I got fed up with poor hot starting and measured voltage drop on the entire system. The 3 foot cable had 1V across it during cranking as measured by a mechanical meter. Since the starter terminals at peak draw measured 4V, 1V wound up being significant. It now starts right up when hot. Monaco assembled the old 4/0 cable with a hammer crimper, which is not ideal. Also the batteries were wired up such that the positive cable was going to the right battery, and the negative cable was going to the left. That has the effect of pushing all current through additional 2/0 cables and fittings, which is not ideal. I connected both terminals to the left battery. Battery cable was made by https://www.custombatterycables.com and the work appeared to be excellent. I upgraded the cables between left and center batteries to 3/0 because I'm neurotic. Attached is a photo of the old cable with the SGX insulation stripped off and oxidation starting at the end. Hoping this helps someone else with hard starting issues. Thanks, Rob

At least on our ISX, the lift pump doesn't pull air well enough to prime the system with dry filters. Racor used to make fuel/water separators with a hand pump on them, but they appear to have discontinued those.

When draining the water separator, do it when the tank is full and the coach is level. I've heard air sucking in before when cracking the valve and not meeting these conditions. Doesn't take much air in the top of the filter to break the siphon. From a previous experience running the tank too low parked on an incline, I learned the water separator must be removed and filled with fuel several times in order to get the primary fuel filter primed. I wasn't able to crawl under and fill the primary, but I'm sure that would have been faster.