Help needed with 1999 Gem, E825

I just received a 1999 Gem, E825 with only previous knowledge that a couple people worked on it extensively and couldn’t get it running. I have an excellent background in electrical, but have no previous knowledge on 72 volt gem cars and have no schematic. The dash was removed and the DC/DC converter was laying on the floorboard. It is apparently an updated “Sure Power” model 71030i. I did a fair amount of troubleshooting and got the key switch to bring in the fuse panel and now the turn signals, horn, wipers work when key switch is on. I do not understand how I can get the 72 volts to bring in the main contactor when this converter does not supply a 72 volt “Keyed on” source. Where do I get the key switched 72 volts when the 12 volt source from the converter is what is switching the other 12 volt power from the DC/DC Converter?? I have no BDI when the switch is turned on, except a momentary 11 and then 127 when the main bat. switch is turned on, then blank… The key switch makes no difference. Any advice or tech data would be appreciated.
Thanks, Len

The 72v comes from the central distribution.

For testing you can run B+ direct to high side of contactor coil.
The low side comes from p11 of the controller. The controller has the “line contactor coil driver”. It pulls in when safe to do so.

Do you get “switched” 72v anyplace?
I believe you need the charger interlock connected for that.

This might be close.

Thanks for the fast reply. I don’t understand what the “Central Distribution” refers to. The only 72 volts I can find is on whenever the Battery Switch is turned on. I cannot find any “Key Switched” 72 v. power, which would be absolutely necessary in bringing in the Main Contactor. I did Plunger the Main Contactor manually and witnessed no changes at all. No BDI, sounds, etc. I do not yet have the ability to read the attached drawing although I’m hoping it has the “Sure Power” DC / DC Converter that I have, which has no 72 volt, switch controlled output. I do have a download of the service manual, but it does not address the DC/DC converter I have. From the drawings I have, it appears that the “Key Switched” +72 V. is also required on Pin 1 of the Motor Controller, as well as the -72V. from the “Key Switched” Blk/Grn wire on Pin 11 of the Motor Controller. I don’t appear to have anything at either of these points. When I plug the Charger in, within a very short time, I get a flashing red light and a pulsing beep from within the charger. Can’t find any info on the “Beeping” coming from the charger. Also. If I put it in the “Turf” mode, I get a Beeping from another buzzer located externally near the Main Contactor. It has 72 V. on it, but is rated for 10 - 48 volts?? I may be getting ahead, because my next objective is to get the “Main Contactor” to pull in when I turn the key switch to on. I understand that the previous owners original problems started when he dropped something across the battery posts and that’s when it quit. I may have a bad “Motor Controller”, but want to be sure before purchasing.
Appreciate your help,

additionally, I have fairly new batteries (Trojan 30XHS), which I charged individually and have a total Voltage of approx. 77 V… The Charger is a ZIVAN.

You may have to hot wire some things to test them, if you don’t have 72v anywhere.

To partially test controller and bdi connect 72v to pin 1. Pin 1 should have power all the time.

Then connect 72v to pin 2. That simulates turning the key switch on.

The bdi should come on at that point.

If not check pin 15 for 12vdc. If no 12vdc when p2 has 72v, controller has problems.
If you have 12vdc then check the smaller bdi plug, p5 for +5vdc.

Bdi will come on with no other connections other than p1, p2, and main B- cable from battery.
It can even be checked and programmed out of the car with lower voltage.

Thanks. That info is what I was looking for and makes sense. I will try it out and get back. Since the BDI gives a momentary readout, I feel confident that the gauge itself is good. I was considering putting in another 12 V.D.C. relay powered by the switched 12 v. and run the 72 v. through it’s contacts to the various control voltage points.

What you are considering makes sense. Even though you may not find relays with 72vdc contacts, it may be more reliable and easier to service than original.

Don’t you love the wiring diagrams supplied by manufacturers.

Just enough information for a parts switcher to start his guessing game.

What good are empty boxes showing pin numbers, but no voltage readings or internal connections? :rolleyes:

Hi ,
I had a similar problem with my 1999 Gem. The problem turned out to be the charger interlock. If the charger is plugged in, it disables starting the car.
Also, does you car have the original 72v to 12 vdc convertor box or the newer model which is sealed? The manufacturer is SPS Electronics , SPS Electronics they located in SPS Electronics Incorporated
8005 Island Road - Eden Prairie, MN 55347
Phone: 952.934.7004 Fax: 952.934.8882
They still have a stock of new old stock replacement modules and are very knowledgeable on the GEM electrics
Yuma, AZ

Email me and I will send you the DC/DC converter upgrade information which has the wiring schematics not shown on your electrical diagram.


Thanks for all the input. I checked pin 1 on the Motor Controller and had a fixed 72 Volts. I checked pin 2 and did not, even with the key switch on. I traced the wiring back and discovered I “did” have a 12 volt operated relay (slightly hidden) with 72 volts on the contacts. I did not have the 12 volts to energize the coil when the key switch was operated. I tapped into another “switched” 12 volt source and took it to the relay. Boom, contactor came in, BDI came up and I took it out for a drive shortly there-after. Thank you “More Voltage Please”. I still have minor issues with lighting, etc., but I am “over the hump”.
It appears that the charger is also working correctly. The only major question I have is; where does the charger overtemp bulb fasten. It obviously should contact a battery, but I cannot find anywhere a description of where or how it locates?? it was just rolled up.
I do agree with the post on the poor schematics and descriptives. I have been an electrician on homes, helicopters, lasers, robotics and high end machines for 45 yrs and this little guy was kicking my but. Thank you for your input.
For the gentleman asking about my DC/DC Controller; it is a Sure Power, Model: 71030i. with a Zivan Charger and a Trans2 / GE / IC3645SH7R353TI Motor Controller.

I believe the overtemp bulb you refer to is the remote red yellow green charger indicator. It is usually mounted above the BDI in the steering dashboard. The other should have a 4 pin plug that plugs into the top of the Zivan.

The newer chargers use a sensor potted in a large crimp terminal with 5/16" ring to fit a battery terminal bolt.

The reason for no B+ to key and p2 might be the charger interlock circuit.

B- or B+ are supplied by charger. Key circuit goes dead when charger is connected to ac.

“Old Houseboater"
yes, I have the BDI indicator LED which changes from green, yellow, red and the multi-pin plug at the Charger. It is the Temp Bulb itself l am having trouble finding a location for. The end is about 5/16” dia. X 1 1/2" long and has course threads in it’s tubular plastic end and its cable is routed to the front batteries.
"More Voltage Please"
I will check the battery terminals on the front batteries for such a mount. Thanks for the info.
I have been working on the lighting and am down to the front turn signals, but your right on the “Key Switch” circuit passing through the Battery Charger. This is what I originally bypassed to get it going. I really don’t know if this is a problem or not, but is on my to-do list before dressing out the wiring.
I just got done removing the brake switches. One was stuck, which I lubricated with silicoln spray and resurrected and the other was out of adjustment. All works good now. Interesting how they have the Safety circuit incorporated into it.
Once again, Thank You so much.
I have been also Cleaning up the Hood, fender flares, rear covers and getting them mounted. Actually from being a pile of dirty parts, It is really going to be sharp when finished and it appears to have everything needed for completion. I had to epoxy one headlight bracket back in and epoxy the hood strap retainer back on and rebuild the front wiring harness. the hood was held on with bailing wire. I redid the hinges and it works great.
Thanks again,