Rigmaster

I was having the same issues. Went through and unplugged wires from the sensors and plugged them back in to make sure there was a good connection.

 

That's good. It's pretty sad that I knew what was lose just from your description and error code, lol. I've got over 5,000 hours on mine and I haven't had any major issues, but I keep a very close eye it. I know the book says to do a pm every 1000 hours, I've found that doing them every 400-500 hours has really been the key to keeping in running. If you look up the old service manuals for the rigmaster apu, it use to have a service interval of 400-500 hours, not this 1000 hours they show now. Last time I was at Bus N Truck they replaced the water pump and main seal. Water pump was leaking but it wasn't to the point of failure or anything.

Other things that help, wash the engine every couple of months and get that road crap off and out of there.

The belt in the back that operates the alternator and water pump, when it gets loose you'll start to see a drop in the alternator volt output. If you miss that sign, it'll start to squeal letting you know it is loose. Doesn't mean you need to replace it, just means you need to loosen the bolt on the alternator and use a pry bar to push it further out from the engine so you tighten up the slack in the belt.

When you're at Bus N Truck, pick up an extra set of filters and belts, that way you can do the oil change yourself or if you have a TA/Petro do it you'll have the filters because they don't always have them in stock.

Hope that all helps.

 

I don't do that. Probably one of many things I don't follow in that manual, LOL

 

Yes, it happens after a pm sometimes, I think they just bump a wire with crappy connectors.

 

I am sorry for your unfortunate ⛵ ⚓ acquisition, would see about getting it working ok & trading it in for a used Tripac before it blows itself apart.

We are on Rigmaster #5 at Prime & have seen literally everything that could break in in every conceivable way do just that.
They are of a design weaker then the sum of their parts & susceptible to many failings -

External temp sensor unreliable causing glow plugs not to fire for as long as they should have per temperature range outside causing multi start/hard start/no start & early glow plug failure.

Keep your oil level no higher than the middle of the low/high markings or you will blow gaskets from overpressure on cold day cold starts

Air filter clogs easily & quickly, might want to fab up a simple stocking prefilter to help prolong replacement.

Coolant reserve tank cap with hole in it on hot days will allow coolant to boil out that hole & onto belt positioned directly beneath it destroying the belt very quickly & causing unholy screeching until that point - install a hose nipple horizontally at top of tank with 3/8" radiator tubing to direct coolant directly to the ground instead.

Change the default battery charge start voltage from 11.9V to 12.5V or your batteries will fail much sooner.

If you have the secondary cooling fan on the bottom, it should be moved to the vertical left side of engine with a new cutout on the casing.
You can see this was done on the latest models with the Kohler engine & rounded casing as well as Tripacs mount similarly, albeit on the vertical right side instead.
The heat from sitting on hot asphalt combined with ambient heat from engine running was seizing fan bearings & reducing cooling efficiency significantly.

Depending on generation/model, (Prime versions were all Rigmaster inverter models) the alternator is probably undersized for running anything more than charging batteries.
When we run a microwave/blow dryer, the alternator can't keep voltage up, not good for batteries/inverter/electronics ect. as evidenced by us going on our 4th inverter.
Tech recommended running truck engine at high idle for high battery drain appliances instead of APU.

Just some of many that pop to the forefront of memory.
Glad Prime is done with them & going with Tripacs again.

Error 4/7 can be traced to many issues, one of the most frustrating & random was one we had on a brand new unit with less than 1000hrs - check your engine speed sensor; if it malfunctions, the engine will think it is running & stop trying to start.

 

Old timer once told me the surest & best fix for our crap blasters. Works every time....guaranteed!

Loosen all the mounting bolts as much as you can before you take off next time.

Problem solved!