Generator Blower Help - Advice and Expertise Needed

A week or so ago, I posted a problem I was having with my generator blower not working properly. It would shut down and then not restart for several hours. After checking all fuses, connections and power to the electric motor it appeared that the thermal protection on the motor was shutting it down. I'm traveling across country so I replaced the 14 year old motor but the electrical supply house only had a motor with a manual reset. I installed the new motor and within 30 - 40 minutes of operation, it shut down again. (thermal protection switch). The water temperature in the radiator when the blower is running is about 165 - 170 degrees depending on the load. This seems to indicate that the radiator is functioning properly. To be safe, I replaced the engine thermostat and replaced both radiator caps. I've managed to keep the generator from overheating when the fan stops by keeping a watch on the gauges and shutting down the generator when the blower light goes out.*

The exhaust baffle is new. It is in place and clear of any debris. The inlet for air flow to the radiator is open and clear of any debris. The coolant is clean and at the proper levels. Yesterday, the generator and blower worked properly for three hours while the bus was moving. Then suddenly the blower stopped. I know nothing about the two relays in the watchdog but would they have any impact on the fan motor overheating and shutting down? The squirrel fan that draws air through the radiator does not appear to have any issues. It spins freely and the shaft has no play. The motor drives the fan in the proper direction and it exhausts heat through the baffle.

The motor does not appear to be in a bind. It sits properly on the mounts and is lined up with the fans pulley. The fan belt is not too tight as to cause an overload. I'm stumped and looking for any advice!
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Thanks,
Richard Barnes

Is the blower motor the right horsepower?Take an amp reading of the blower and if it more than the motor is rated for it should do exactly as you described.Also I recently replaced a fan motor in my plant and the data plate on the fan was incorrect and after a few minutes it overheated and shut down,this is the second time this has happened in my plant in almost 30 years.

I see you checked the air intake to be clear. Have you checked the air exhaust port to mak sure it clear. If you're pumping in air with a space with no exit, a pressure positive situstion can develop where your fan cavitates and there is no actual air flow.

Richard, ask liberty for the specs of the original equipment motor installed by them. Maybe someone before you changed out the motor and settled for something close and inadequate and although you duplicated it you now have the wrong motor. The only thing you didn't mention you checked in the replacement of the motor is the RPM of each motor. There are also pulley diameters to be considered.

JIM

I think that Jim and I are saying about the same thing,the motor is the wrong horse power or the RPM is wrong,or possibly the data plate is wrong.I have also had capacitor start motors that have hung in the start mode and overheated in a few minutes.

Thanks guys! I'll check the amps tomorrow but the plate on the new motor is the same as the old motor. 1 hp, 1725 rpm, etc. I'll call Liberty tomorrow - that's a good suggestion. Do you think there would be any problem putting a 1 1/2 hp 16.5 amp motor in rather than the 1hp 14 amp current one?

Find out how much current it is pulling and then you can make a decision,I purchased a new motor that should have been 1075 rpm but was actually 1625 rpm and when we checked the amperage it was obvious that the data plate was wrong.

Richard,Have you figured out the problem?