New '06 Gem e2 owner, DOA Possible dc/dc converter bad?

Greetings all! I recently bought a dead project 2006 Gem and have spent the last month or so searching the forum here to learn what I can on how to repair it. I did get a pdf service manual from Rodney here (a BIG thank you!) and that along with the advice/solutions the group here has offered to others it has given me hope that I can resurrect this Gem to a working EV again. :slightly_smiling_face:

A little info on the Gem, it’s an '06 2 seat model, Blue Max motor, Delta Q charger, Sure-Power dc converter, 14" wheels & a stake bed. Overall fairly stock, the only change other than the motor is the key on switch had been replaced w/an on-off rocker switch.
I bought this from another forum member here after he had problems with a new gel battery set installation. Within a few days of getting it back from the Polaris dealer it died so he took it back and they told him 5 of the 6 batteries were bad. This all started about the same time as covid shutdowns were starting up and in the end this car sat at the dealer for 7 months after which they told him to come and get his car…non-functional and minus the battery pack. I bought it as a non running project with the hopes there was nothing major wrong with it, after all he had no issues with it before it went in for new batteries.

So far I’ve installed a new set of group 31DCM lead acid batteries from OReily’s and cleaned every cable connection. When I powered it up (master switch & key switch on) I was bummed but not surprised that nothing came on, no lcd dash, no lights but the parking brake buzzer can really sing.

I’ve run thru the drive/power system troubleshooting “chart A” several times and I always end up w/a fault at step 12, no 12v @ fuse # 9. The manual says to replace the PSDM.
On a hunch I then checked the dc/dc converter using the accessory chart and while I have 72+ & 72- vdc (pins 12 & 1) @ the converter, I don’t have 12v @ pins 7 or 8 going out. This seems to point to a bad dc converter and possibly not a psdm? I wasn’t sure what the dark blue wire (dc/dc enable, pin 3 on converter) is for, does it control the function of the converter?

Any advice for further testing/diagnostics from the pros here will be greatly appreciated!

Here it is when I first got it home. Overall in very good condition, it just needs to get some power to the wheels!

I remember this tragic story. The guy seemed so frustrated that he couldn’t even look at his car.

However, I need you to look at something else. Your car may not be wired exactly this way, but it gives a clue to what the outputs do on the DC Converter.

Note that p7 and p8 are Switched 12v. You won’t see anything on those until the purple wire off p3 goes high [12v].

What do you get on p9 and p10? Those should be 12v constant and feeding the fuse panel.

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Yes, he had a not so pleasant experience with them to say the least. :confounded:

I get nothing off of either pins 9 & 10 (white wires). I did remove the converter and pulled it into the cab area for easier testing so I’m able to get a straight pin into the back side of the connectors for voltage checks while the converter is plugged in.

…and no 12v at any fuses in the fuse panel either. I see some later model dc/dc converters with an external fuse access on the aluminum case but mine does not have that feature.

And you are using the black wires on 4,5,6 for -(NEG) reference - yes?

Then I’d say this is the first thing that needs to be replaced. There should be some output here.

I have not been into one of those yet. Not sure if it is worth it, or maybe you would discover a board mounted fuse that could be replaced or jumped. Normally the DC converter would protect itself and shut down if a high load is pulled. If not removed it would keep coming back up and going back down again. Click, click, click. Probably until the battery was exhausted.

The “curious me” would pop off an inspection plate or two and see how far I could get in there and how much of it is potted.

The “rebel me” would say, “It’s just a 12v supply”, and start scrounging around for a stray 12v battery. Make sure a small (15/20A) fuse is in line. If something downstream took out the DC converter, it may still be shorted.

How much of the dash do you have taken apart? It might be interesting to poke around in there and see if there are any traces of what a 7 month diagnostic at the dealer looks like.

Edit: I saw someone selling a converter over in the classified section just the other day, but someone was nipping at it. It might be spoken for.
I went and looked and it was you!

I do have the upper/lower dash off & there’s no real evidence of burnt, cut or repaired wiring…just the key switch being replaced with a rocker switch (steering column cover is off too). I did also pull, inspect and reseat all of the connectors going to the psdm, controller and the converter…nothing strange there. I did pull the psdm from the dash mount and did not see any corrosion or melted sections on it, at least from the backside of the circuit board.

edit: And yes, checking with the 12v ground at the black wires from the converter. I also checked and have continuity from those to chassis ground.

This converter is a sealed unit, one piece finned aluminum case that is epoxy filled on both ends so it may take some doing to see if there is an internal fuse. I do have a line on a replacement converter, I just don’t want to plug it in only to find there are no changes and something goes poof!

Are these converters that sensitive and go bad easily?

I did pull the psdm from the dash mount

Oh MAN!!! You were right there!!!
If you feel inspired to do that again, it’s a good time to put a nice piece of tape over that ear splitting Back-up/Brake beeper. I shoved a piece of foam in mine. It’s kinda hard to tell how much to tone it down without reinstalling it but anything is better than wide open!

Are these converters that sensitive and go bad easily?

Actually no, (I don’t think so).
They shut down on high draw then reset.
It makes for some real confusing power cycle issues before I remember about it likes to save itself.

edit: And yes, checking with the 12v ground at the black wires from the converter. I also checked and have continuity from those to chassis ground.

Good- That was a trick question, and you passed.
Now that I think about it…
Depending on where you are with it, Maybe remove that ground lug from the frame (since it is easiest without butchering the wiring) and see if it wakes up? (I doubt it, but just a wild idea)

(thinking it would remove the load/short)

I’ll try that tomorrow, sure can’t hurt to try. I don’t see any spark or arcing when I connect the batteries or plug in the converter.

You would think that darn parking brake beeper would wake up just about anything! :upside_down_face:

Just wanted to let you know. I sold the car to a gentlemen that has the knowledge and the time to fix it up.
I tried to cancel my add but could not figure out how to do it.
Thanks for all your help it is appreciated.

Something doesn’t make sense. No voltage out of the constant 12v on Dc converter but the buzzer works. Buzzer can’t work without power .

That’s what I thought too and initially felt the converter had to be working but after looking at the schematics (manual page# 5-46) I see that the buzzer is powered by 72 volts. A voltage check @ the brake switch confirms 72v. I guess that’s why that thing is so loud!

IF you have 72v going into converter( use battery negative when checking) and nothing out, its bad. I have seen them burn out before.

No, but not reverse polarity protected. Often burnt out after changing batteries. I think you can guess how that is done. :slight_smile: Been there done that!

Well that may be a strong possibility since the problems with this car seem to have started after the dealership battery change out…who knows what really happened there.
When I got it there were no batteries in it so I searched the forum here for the proper cable/battery layout. It took some searching but I did find several pics of the right battery/cable configuration.

Hopefully the converter is the only part that got damaged, are the psdm’s also not reverse polarity protected?

I believe you know, now. :slight_smile:

@Inwo - Would you object to my thoughts of hooking up another 12v source(battery on the floor) to see if the car wakes up? (Just until his new converter arrives)

I’d study the wiring diagram a bit to find the best place to inject power. If it could be put in on those Acc tabs on the PSDM or if better(but more difficult) to go in at the DC Conv plug. It won’t switch the car on/off with the key(now a toggle switch), but this is only for testing.

Just a quick update. The dc/dc controller was bad. I got the new controller today, plugged it in & the gem came back to life. Now on to fix some of the other problems with it but at least it has a heartbeat again. :grinning:
Thanks again for the help here!