trailmug

This one's a picture from the Sanden failure modes analysis PDF, though mine looked rather similar

If using dye, make absolutely certain it's compatible with PAG.. mineral oil dye will do this (I believe what happened to mine):

Along these lines, when parking, turn the system to OFF or MAX for several seconds before shutting the engine off, or the outside air damper remains open (at least on ours). More stuff for the checklist.. these things are a lot like airplanes 🙂 Sanden compressors are supposed to use 5HP or less.. I think most of the summer fuel burn comes from the higher demands on the engine fan.. unless your engine fan doubles as your condenser fan, and then that makes total sense.

My money's on there's a leak and the switch is sticky. I expect spring will find you in the same situation, but you've got a head start on it. 🙂

We're preparing to think about selling a 2008 45' Sig with wheelchair modifications, four slides.

Bingo, 4475/4756 is for use with the Cummins water pump pulley. Only notable difference between those two is the electrical connector, which I had to swap.

Non-use can lead to drying/leaking of the compressor shaft seal.. explains the missing refrigerant but not the dry crankcase. I ended up needing 400cc oil in a flushed 45' system (new condenser, compressor, receiver) to get the right amount of oil in the compressor per dipstick method (I didn't use the RPM/drain method because getting to my compressor is a bear. If you do the RPM and drain method, do the math on the pulley sizes because the spec is for compressor RPM, not engine RPM). Wouldn't surprise me if it was low on oil from the beginning. FYI, took me 2 hrs of vacuuming after flushing to get a steady vacuum per micron gauge. I'd be tempted to start with 200cc in the crankcase. I believe the Sanden manual has suggested oil make-up amounts for various replaced components. In my experience, the long suction line (and what I presume is oil pooling in it) tends to make the low side pressure at the rear service ports lower than what the evaporator saturation pressure would give you (15 PSI lower for me). Opening the compressor clutch circuit would cause the gauge to immediately rise to the expected sat pressure. At the risk of being too verbose, I was able to feed the entire 4lb charge as liquid into the high side of the evacuated system (evap fan running). Super fast and easy that way. If you don't have a bulk tank, you can get your 609 certification online at Mainstream Engineering (I did) 🙂

Might be able to use standard bolt torque for the fastener size/grade. I've always gone with "snug" for stuff not involving a gasket. Are you planning to leak check before the repair? Maybe put a 134a vapor charge on it and go around with a sniffer? Sometimes stuff will leak under pressure but not under vacuum.

One last suggestion if you are going to swap the compressor, there are holes in the mounting bosses for penetrating oil. Use them, I snapped a bolt and had to take the thing off with a chisel and saw.

I would put money on finding a leak at a hose crimp (Monaco field assembled the hoses with a manual crimper.. my own odds with a manual crimper are about half of them failed.) Gates brand fittings were much more reliable in my experience when using a MasterCool crimper. The only hose+fittings you can find these days that are engineered as a system are reduced barrier hoses, so you're kind of on your own to try it and see what holds. I had ParkerStore make me a compressor discharge hose with Tube-O and MIO fittings (for an arm and a leg) to reduce the number of crimps I had to make. Would absolutely do that again. Figuring out all the industry terms for the various fittings was a treat, especially since it's not the same across brands.

As I understand it, receiver is on the high side after the condenser, accumulator is on the suction side before the compressor. Both are used to store desiccant (pretty sure it's in a bag below the screen) and provide rudimentary filtering. I've heard a dedicated inline filter is better but if you have chunks floating around, I guess you've probably already lost 😁 Also you can't see it in that photo, but the screen with the big holes sandwiches a smaller screen, maybe the coarseness of a window screen or a bit finer.

PAG oil holds onto moisture.. if you have an inkling to replace the compressor, do that (and get an O ring kit) and definitely swap the receiver/dryer. That should mean you're good on oil unless you flush lines, then I'd add a few ounces for the long lineset If you replace the receiver/dryer, I'd cut it open. Check out what mine looked like (and what led to a flush).

Misplaced (and malfunctioning) frost sensor? I think that's basically the only cycling control these have.

Air in the system causes intermittent high side pressure spikes.. I'm with Bob, I doubt the gauges. Our coach was contaminated so badly when we bought it that it trashed a gauge set with sludge. (I think somebody put mineral oil-based UV dye in it.) Also, the service valve cap is the primary seal.. the service valves are only there to give you time to get the cap back on.

Suction pressure will be low due to the long suction hose. 15 PSI isn't out of the ball park in my experience, but that high pressure is low for sure. What are you using to measure the charge, a bulk tank and a scale? Also stupid question, but you turned the quick couplers clockwise to depress the service valve cores, right?

Is the charger temperature-compensating? Hot batteries like low charging voltage, cold batteries want it high. Rate (amps) would be the same for two series batteries as a single, voltage obviously is doubled.

It's unfortunate that motorhomes have 12V house systems.. at 48V, this would be easy (1/4 the amps).

Agree with the general sentiment on the thread already.. Even with 8 GC2 batteries for 860Ah on the Sig, the microwave (roughly the same load as an A/C) on our inverter pulls the DC voltage down into the dubious range (10.5-10.8V) on anything but a full charge, and the sine wave starts to suffer, which will cause motors/compressors to run hot and appliances without switching power supplies to groan (our refrigerator lights flicker). I wouldn't want to do it for an extended period.

I think it's a common issue.. maybe restrictive return creating a vaccum on the evap drain. Ours has done it for years, don't pull out of the driveway with the driver window down! 😂 I wonder if they (should) include a trap like you need on a downflow residential unit.

The "hat" to the right of the yellow label with the tiny copper tube is your TXV. As an aside, this particular photo appears to show the pressure switch (screwed onto the receiver/dryer) with no wires attached to it.

I would also add that if the system took a can of refrigerant while the compressor was not running, it has a major leak and was empty. If the system had liquid, and the can had liquid, and both were at ambient temperature, there would be essentially no flow of refrigerant from the can because they'd be at the same pressure.

I'm with Ivan on the suspect pressure switch.. jumper the pressure switch terminals (usually up front near the receiver) and see if the compressor engages. Those binary switches are pieces of crap. Don't run it that way for long, though, just enough to verify. Low refrigerant would mean low oil circulation.

Battery technology can't come anywhere near the power density of a diesel tank, plus recharge can be had immediately for $$. Best we do with two panels on our rig is break even with the daytime standby loads. It'd work as a battery tender (salesman switch open), but it would take a lot of determination and some good luck (weather) to live off of what you can fit on the roof.

Agreed, I manually change to furnace around 40-45F .. The heat pump beats itself up icing and deicing (can hear the cracking sounds on defrost), and doesn't seem to do much useful work below that. Also, I notice if we're near border temperature, the cold discharge air from the outside coil will cause the system to flip back and forth ("Oh it's colder now, go to furnace; oh it's not so cold, back to heat pump..")

I like the idea of a Cat's Eye or Crossfire.. I bought a pair for my dually axle but never installed them. A good deal of the reason why is I had a leaking stainless hose valve extender, and had a commercial tire tech say that they're junk and recommended installing extended rigid valve stems, advice which I happily accepted. You're a step ahead with the TPMS and will never have to worry about a concealed flat. I think realistically there's always some scuffing between dual tires owing to difference in road crown, temperature, etc, but figure if it's a big concern, the big rig world would have fixed it.