MEP-531A HZ Frequency Meter

I recently acquired a 531A and was able to get it running .... using the TM .... but have run into an issue I can’t find addressed in the TM. The engine appears to be running correctly but on initial start up, the Hertz meter is pegged to the far right and volts and % power are barely registering, even with a load. The low electrical output indication appears correct as the output will barely start a portable fan.
Sometimes (more often than not), the HZ meter will reverse (peg far left) and the volts will move to the green and the % power indicates correctly. At this time, the unit has enough power to run a chop saw .... % power initially jumps to 110%+ on start-up of the saw but drops to sub 50% once the saw is running. Again, appears to be operating correctly at this point with the exception of the HZ meter pegged low. Any suggestions?

https://cdn.greenmountaingenerators...-and-Special-Tools-List-TM-9-6115-673-13P.pdf

Sent from my SM-G975U using Tapatalk

Might ask Guyfang

Sent from my SM-G975U using Tapatalk

Verify the volt and frequency meters are reading correctly by checking with a DMM. Let us know what you find.

With the engine running (initial start) but prior to turning the power output on, the hertz meter on the 531a is pegged far right, no indication of load or volts on either 531a meter. On the mm, hertz or voltage are 0.

When the electric power switch is turned on, the 531a’s hz meter is still pegged far right. The mm reads 52 hz and 29v. The 531a’s voltage meter appears accurate. It it will typically remain in this state until the generator powers an external device - in this case a fan.

After 15-30 seconds of powering an external device, the gauges on the 531a will very quickly reverse in sync. The 531a’s hz meter is pegs far left (zero) and the voltage meter goes to the bottom of the green. The load meter shows approx 25%. The mm reads 52 hz and 116v. The unit’s voltage meter appears accurate.

If I adjust the 531A’s potentiometer to try to increase the the voltage above 116, it will very quickly reverse and go back to the initial “power applied” stage - with the 531a’s hz meter pegged far right and voltage indicating 30v. On the mm, hz will oscillate from 52-63 for about 15 seconds and settle out at 52 hz. The MM voltage reading will also oscillate but will settle at 29v.

Now that I’ve run it a few more times, the initial reversing process happens on initial start-up - with the engine started but electric power not switched on yet - the 531a’s hz meter is pegged far right and voltage very low. After about three seconds they will reverse - with the 531a’s hz meter pegged far left (zero) and the voltage meter going to the bottom of the green. The mm shows no hz or voltage until the power switch is turned on - it then goes to 52 hz and 116v.

1. Any thoughts on how to fix it are appreciated.
2. I plan to run power tools and a small ac unit off of it. Will running those at 52hz and 116 v cause damage to them or the 531a?




thanks in advance.

I finally was able to reach a Dewey engineer. Counter to my expectations, he was extremely helpful. Using a mm crossing the 5th and 6th (from left) terminals on the wiring block, I was able to determine the engine was running at 3100 rpm instead of 3600 (310 hz reading * 10) - which caused the 52hz and voltage maxing out at 116. I was maxing out the voltage potentiometer setting. Once I adjusted the throttle body plate (adjusted position on slotted side)to increase the engine rpm, volts showed 130 on the mm (which I adjusted down to 120) and hz is now 57. The 531A’s hz meter now works.

Question: I’ve maxed out the throttle body setting to increase rpm. According to the Dewey tech, the only other way to increase rpm (I.e. get to 60 hz) is to change the governor inside the block. Is 57 hz close enough?

57Hz will run most consumer electronics. With that said, that engine should have no problem turning fast enough to put out 62 or 63Hz. I have seen a few 2kWs with wet stacked exhaust systems that can severely limit power. Pull off the spark arrestor and look for clogged discs and carbon build up. If you find a lot of carbon gunk, clean everything and then put as much load on it as it will hold it for an hour. Use 500W halogen lights, heat guns, etc.EDIT: spelling

Any updates?