Home Forums General Discussion Technical Questions Montgomery Miprom 21 DDC controller drive issues

I have this unit that has been recently shutting done with a 37 motion fault. The CPU does not see the BC (balance complete indicator) go high. It is a hard fault that on the service tool says retry limit error. I replaced all the aux. "M" contacts, the "PR" relay the "P" relay on the interface board and the "PA" relay on the pilot board. I checked my drive power supplies and they are good. I have looked over the Allen Bradley contactor and I question it. This unit is about 13 years old and the movable part of the contactor shows wear. Do I have a bad MSU board? I will swap it out monday. The contactor is what controls the aux. "M" contacts, so is it maybe my problem? This is a series A drive. Any help would be great, and you will be helping out your iuec brother.

You're on the right track...Happens as the car starts or in flight? Hmm..BC controlled by BCX???...Hmmm...

It happens before the car even gets a chance to move. I first found one of the n/o aux. contacts not making earlier this week. I replaced them and it ran fine for a day and then started doing it again. That is when I replaced the other n/o and the n/c aux. contacts. The n/c and n/o are all in one stacked on top of each other unlike the seperate n/o.

yeah...without Balance Complete yer goin' nowhere. now isn't there a tiny BCX 24v relay on the interface board? how about replacing the BC relay...I didn't see you mention that. but...the line for BC is where your gonna find the trouble. retry limit error is after so many attempts to start (like 3) and it can't...shut down time.

Replaced "BCX", "BC" all 3 aux. "M" contacts on drive contactor, "PR" relay and the drive contactor. Also replaced the MSU board and miprom power supply. Have CPU and relay interface board coming in the morning.

I'm having the same problem...what did you find?

Chances are the relay interface board is the problem. If not you may need a motion adapter board. These types of problems are tough to find without having boards to replace so as to eliminate them from your thinking one by one.

The M contactor if worn may be hanging up as it tries to pull in. Also make sure the coil is not flaking out intermittently, and there are no loose connections in the coil circuit.