Generac Generator 75D Problems

Start off by doing diagnostics on the engine temp and oil pressure emergency shutdown circuits.

That’s where I’d start too. Make sure the oil level is in fact at the top of the fill zone before going any further.

On other Generac engines I’ve had, the oil temperature and oil pressure switches were on the same circuit. Oil pressure is a normally closed switch (oil pressure holds it open), and oil temperature is a normally open switch (over temp closes it). If either switch completes the circuit, the engine shuts down. You can unplug both of them for long enough to determine if they are faulty or not.

On my Generac home standby generator, I determined the oil temperature switch was bad, bought a new one and when I went to replace it, it fell apart when I removed the screws that were holding it to the engine.

:):)

Sounds like a cooling problem. Are you checking coolant level at rad pressure cap, rather than just visibly looking at overflow tank?
The cap is under a small flap, just above control panel of gen; one screw holds it in place. Check the cooling fan blower belt, make sure lots of cooling air coming out at the bottom of set. The end panel of this set is usualiy easy to remove, take a dozen or so 1/4 bolts out.Then you can visibly check belts, etc. The oil pressure switch is readily accessible, in cyl head near front of head. The hi water temp switch not so...it is around on other side of head near thermostat. The control panel also has a overspeed shutdown function, very sensitive, can be adjusted, if you remove odd shaped plate on left side of gen, gives you access to control board and voltage regulator

Took the MH in to a certified generac dealer this morning. They found some wires that were too close to the flywheel, one of them was cut. They fixed that, but to get to it they had to pull the panel that has all the buttons and oil fill and dipstick are on. Then as he was about to remove the coolant tank he found that the tubing that feeds the radiator when needed was kinked and that for some reason was not down completely in the plastic tank. After fixing both problems, we fired the genny up and let it run for about 20 mins. No problem, then we turned both a/c's and again NO PROBLEM. Total cost with these guys was $143.78. In a few mins I'm going to take the MH out on the freeway for a test while driving. Keep your fingers crossed.

KRAP happens on a 19-year-old Genset. Especially a Generac. The YUGO of generator assemblers.

Took her on a 30 mile freeway ride with genny and both a/c's running. Not a hiccup at all.

I have worked on many Generac diesels and once the garbage is corrected like harnesses fill tubes regulators their reliability improves markedly.

Onan had industry-leading failures with the remote start harness at the generator. Onan use genuine MOLEX gold plated MOLEX connectors? Hell no. They saved four dollars by using a nineteen cent play-toy plastic connector.

Thirty years ago I took a full carton of MOLEX threaded connectors to Mexico and made a fortune visiting remote beaches. I ran out of them by the time I reached Puerto Vallarta. The metal connectors looked so impressive they sold themselves. One beach north of Mazatlan I installed twelve of them. Smart RV'ers listened to tales of woe from others and I converted a dozen before they could fail. So it just isn't generac.

Now the big failure is slide out switches. I have 24 75-amp rated motor reversing switches.