Crown RC3020-30:
Sporadic PMT for FWD/REV

I have an RC3020-30 that will go forward and reverse but then randomly go out either direction and do the PMT before completely dropping out where you have to turn the key off and back on. Sometimes after turning the key off and then back on it will fix it and other times it won't. After sitting for the weekend not running at all, it was dead in the water this morning again. Finally after turning it off and on several times I was able to get it going. I changed out the third snubber from left and it started working for half a shift but then it is back to doing the same problem. Any advice would be greatly appreciated.
  • Posted 23 Aug 2022 03:45
  • Discussion started by tg0486
  • Missouri, United States
Showing items 1 - 15 of 28 results.
Sound like one or more cells going open circuit during load on battery.
Technical Specialist
So, I apologize. For some reason, I thought you were working with an EV1 system. Disregard my input. My fault for not asking.
  • Posted 26 Aug 2022 08:36
  • Reply by ErichO
  • Washington, United States
I do have the G.E. handset and that is a good idea I forget about that function, i just checked for a code on it. I was getting -45 on it when it fails but reading in the book so far it didn't help me much. I will read again how to do the tune up and perform that in the morning as my shift is about to end for the day.

If you guys still think of anymore ideas feel free to keep them coming and i appreciate all of the help.
  • Posted 26 Aug 2022 06:00
  • Reply by tg0486
  • Missouri, United States
If you have the G.E. Handset that plugs into the Oscillator Card, definitely perform a tune up for the card.

You'll need the flow chart that has all of thw Function Values listed on the Values page.
  • Posted 26 Aug 2022 05:57
  • Modified 26 Aug 2022 05:57 by poster
  • Reply by LaGrange
  • Missouri, United States
Strong in mind, Strong in Health.
So you are leaning towards it possibly being the 1Rec?
  • Posted 26 Aug 2022 05:55
  • Reply by tg0486
  • Missouri, United States
Chiming in again, I've seen many a 1recs fail under load. I say many due to how long I've been in the industry. Easy to duplicate by stalling the the drive. The hotter it gets, the sooner it would fail. It would also fail the T2 voltage check when the reset would not work. Often, one would test bad with the handyman tester.
If you replace the rec, be sure t get the insulator with it. You probably knew that.
  • Posted 26 Aug 2022 05:17
  • Reply by ErichO
  • Washington, United States
I have tested these and i'm reading full volts on the right side (as your facing forward standing on the truck) , and half volts on the left side.
  • Posted 26 Aug 2022 04:32
  • Reply by tg0486
  • Missouri, United States
When I say "heat up" I mean after the forklift has been driven more than 10 minutes.

Since the PMT appears right away now, that will help you find the defective part.

There are 2 bolts with 1 cable each that are attached to the 1 REC.

1 Bolt will show full battery volts, the 2nd bolt will show half battery volts.

You'll need to test both Bolts for battery positive, stick your Negative meter lead into a Negative cable and test for Positive volts at those bolts.

Let me know....
  • Posted 26 Aug 2022 04:27
  • Reply by LaGrange
  • Missouri, United States
Strong in mind, Strong in Health.
To help you visualize, are you meaning "heat up" as in running for a bit before it does a PMT or its internal action? The reason I ask is because like this morning when I first showed up for work, I tried it and it did a PMT instantly. Unplugging the main harness a time or two it finally would travel but not all that far.
  • Posted 26 Aug 2022 04:21
  • Reply by tg0486
  • Missouri, United States
Alright, I got to think about this....

The #1 REC could be failing under load, it has happened to me at least twice.

When the #1 REC heats up and can't handle it, it will cause a PMT, I know this for sure.
  • Posted 26 Aug 2022 04:12
  • Modified 26 Aug 2022 04:12 by poster
  • Reply by LaGrange
  • Missouri, United States
Strong in mind, Strong in Health.
I have taken everything out down past the 1 Rec and made sure everything is tight. Still same issue unfortunately. I changed out the Potentiometer hoping that was it and no change.
  • Posted 26 Aug 2022 04:07
  • Reply by tg0486
  • Missouri, United States
Ok I will dig into this part and see if anything is loose. Such a strange issue, it seems to be getting worse, now most of the time when I turn the machine on, it will do a PMT, click click cut out. Unplugging the main harness to the card and plugging it back in doesn't always work now either but is about the only way i can get it to move. Except now when i do get it to finally move it will at most get up to top speed and it drops out.

Not sure if any of that information will help you guys but i wanted to keep you updated on what it is currently doing. Sure has me confused so far.
  • Posted 24 Aug 2022 21:20
  • Reply by tg0486
  • Missouri, United States
Busy at work all day today.

Here is more advice:

The block in between the Snubbers and the #1 Rectifier is called Spider.

Remove the Spider and take a good look at the wire on top of the 1 REC, if it is loose you'll need to tighten the screw.

Before you do that, there is a wire underneath the 1 REC that might also be loose.

You must remove the 1 REC in order to see it and might aswell put a socket on it & tighten it, too.

Reinstall the 1 REC and tighten up everything as you go along.

Then perform a test drive.
  • Posted 24 Aug 2022 11:25
  • Reply by LaGrange
  • Missouri, United States
Strong in mind, Strong in Health.
Try rec 3. I've had that before and replacing rec 3 would fix it.
  • Posted 24 Aug 2022 11:20
  • Reply by marcos_m
  • California, United States
I haven't looked at the manual for the pmt driver troubleshooting yet but i do have another crown i can change out parts to eliminate any possibilities. The 1 Rec seems to test good and the snubber filters are all good, unless it could be the block in between the two.
I've been doing this since 2014 and haven't had to change out anything in this SCR part of the truck besides one snubber one time and the guy that helped me said hes never had to change one in his career so they must be rare as well.

Any more advice is greatly appreciated, i'm definitely scratching my head.
  • Posted 24 Aug 2022 06:15
  • Reply by tg0486
  • Missouri, United States

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