Trailblazer 325 does not increase RPM

[baymee]

SKU 907753001 Ser. MK391541R

Trying to help out with this welder.

The start feature works well but the Auto-Speed and Run positions on the front panel don't change the RPM. I have tried other similar models and after starting, they rev up higher than idle speed with no load.

Contacted the factory rep and the control module which controls the governor rod was replaced, but no change.

Questions:

1. Does a welding load increase the speed through the module? The rod to which the governor control is clamped has no start position, so I guess it controls itself electronically.

2. There is another control at the base of the carb with a single red wire? Does that control anything?

3. I didn't consider that the knob switch could be bad. Is anything behind that switch that could affect the controller?

The pics show the module, which was replaced.

[baymee]

After doing some research, the part that controls the governor is called a stepper motor, Miller part nr. 251214. What I'm looking for is what controls that motor? Is it a control board?

[Weld dr]

The part on the carb is the fuel shut off switch. And yes it is the control board that controls the stepper motor.

[Weld dr]

The part number for the board is 287166 at at a list price at 1,173.62 Power aux. regulator w/program PC.

[Helios]

The part number for the board is 287166 at at a list price at 1,173.62

...or $988 at

https://www.miller4less.com/shop/en/usml/287166

[1997CST]

Make sure the stepper motor turns free with power off. There is a fuse for that regulator board or breaker..
If all that checks out its the regulator board. before replacing make sure there is no visible damage to the front panel board

[baymee]

The stepper motor does turn free with no power. I called a Miller factory service rep and he told me a few things and I found out some other info. If you know the search words, you get more info.

I noticed a burn mark on the cover that shields the PC board up front. I had to "cut" the seam to separate it. This is what I found beneath, shown in the pic. The factory guy made me think there are two boards. He said if I connect a grinder to the 110V GFCI outlets, it should rev up if all is well. Well, there is no power at all and the fuses are all good.

[Weld dr]

There is another board behind the regulator board. I would pull the regulator board and check if it got hit by that heavy burn mark. Never seen that kind of a failure before.

[Mickey(not so fine)]

I have both boards from the same machine on my front counter that have some similar burnt spots from the guys using it having jump started it when their battery cashed out. I dunno if that's what happened on your's, but worth mentioning.

Mickey

[1997CST]

I have both boards from the same machine on my front counter that have some similar burnt spots from the guys using it having jump started it when their battery cashed out. I dunno if that's what happened on your's, but worth mentioning.

Mickey

I just had a similar failure, burn up the same plug. the control board was also fried. You'll need to order that plug and pin assembly (PG28) and have a good pin tool to crimp it. I believe that plug has 2 wires that go to the RPM sensor (RC28) a ground (42) and a wire that goes to the excel module, even if the machine doesn't have excel.

[Mickey(not so fine)]

I keep 'em on the counter to show all the folks that say they jump their machines all the time. You can get away with something 99 times in a row, but the 100th can bite you pretty hard. That was a pretty expensive failure compared to the cost of a new battery.

Mickey

[baymee]

Parts will be ordered. I was wondering where the second board was. I have a pin crimper. Owner claims the battery was never jumped.

[baymee]

I warned the owner that I will change boards in a stati-free environment, but not knowing why one burned, I can't promise that the underlying cause won't happen again. Who knows why it happened? Not from jump-starting according to him.

Tomorrow, I'll locate that second board and see what it looks like. Thanks for that tip.

[1997CST]

I keep 'em on the counter to show all the folks that say they jump their machines all the time. You can get away with something 99 times in a row, but the 100th can bite you pretty hard. That was a pretty expensive failure compared to the cost of a new battery.

Mickey

Tell the new Bobcat owners the same thing. Jumping will take out the fuel/hour/idle module.

[Mickey(not so fine)]

I've gotten to the point of telling anyone with an engine drive machine to NOT jump start their machine...I find myself having to cater to the lowest common denominator. I used to write for television and film around 20 years ago...I had to write everything for a populace with an 8th grade education level. It seems to me that that particular bar has been lowered pretty significantly...maybe a 5th grade level at this point. I really try to avoid being condescending, but the lack of common sense in trying to explain or inform folks makes it very difficult.

Mickey