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· Registered
99 Posts
I run into running EV-1 on a regular basis.

Historically the most likely point of failure is the plug in the back of the oscillator card (the card that flips forward) sells rebuilt cards to fix this problem
(they also have the tech manual for it as a FREE down load).

If the card does not try to close the directional contactors there are several possibilities

-PMT trip
It sees voltage at T2 causing it to believe that the "1A"contactor is welded, a directional contactor is welded , or 1 Rec is shorted.

Just measure from (Batt -) to (T2) .
they are both under the silver tag on the card that identifies their location.

You will detect a voltage because of frame capacitance but it should be greater than 15% and less than 85% of battery voltage, if it isnt the card will not send a signal via terminal R3 to turn the driver for the directional contactor on ( its the small black box with 4 screw terminals)

-SRO trip.
The card needs to see the vehicle in "neutral" before it will close a contactor

No directional input, no brake switches open and the throttle at zero.

-Bad oscillator card.

-The driver (small black box with 4 terms) is bad.

- Bad wiring harness.

But my money is the terminals in the back of the oscillator card have corroded.

· Registered
99 Posts
Running this thing probably costs you more than using a well designed update controller.
I actually have a running EV1B in the shop right now

A Clark EC500-25 made specially for Sears

It was built in 1972 ,and the electrics are good , it's the mast thats worn out.

We are actually debating repaing the mast trunions and using it as a "Shop Truck" because it is so easy and cheap to keep running.

The only reason the OP is having trouble is that they stopped teaching high current DC in school because it isn't used anymore.

I had a two year "Idustrial Electronics" degree , and 7 years working on electronics in the Navy before I started working for my father and it was a STEEP learning curve.

I went from trouble shooting everything from static exciters for 1.75 MW Generators , 20 ton electric winches , The ships telecommunication systems ,Flight deck lighting systems, 360 ton Air Conditioner systems ( With PLC's ) and the ice maker in the Officers Mess.

Then I got out , sat down with a Clark TM-15 ( EV-100 controller ) and was completely mystified.
I could identify the components and test them individualy but using a transformer on a DC system to catch the current spike to the motor and use that to charge a capacitor so it could then be used to reverse bias the SCR to turn it back off,( and rated for 1000 amp) and the act of charging the capacitor reverse biases the SCR you used to connect the capacitor to the main SCR.... I knew what PWM was , but I never saw anything like that before.

I know what ptandjb is going through.

· Registered
99 Posts
Two parallel rows of 5 12v batteries. Talked again with Flight Systems tech support, they recommended re-manufacture even if they bench test the unit good if we wanted reliable operation. If unit is too old to support re-manufacture by them they guaranteed they would have a re-manufactured unit that would work. My uncle is tired if waiting, cost is not a concern anymore, time is. One of his daughters cornered me and said, all he wants in life is to drive this car once around the block before he dies. So tomorrow me and my cousin will visit my indestructible ageless uncle at work, do another test run through then out the unit comes if it fails to run again and i will get Flight Systems on the phone.

Pic below of uncle yesterday with a granddaughter and one of his 18 and counting great-grandchildren. Yes, he would fit right in with ZZ Top.

Yeah the issue is the voltage , if it was 24, 36, or 48v they have them sitting on the shelf for exchange.

· Registered
99 Posts
To All,

I am reposting from last year asking for any available advice as me and my cousin continue to try to help get my uncle’s EV project started in 1984 to a successful conclusion.

I am still trying to help my uncle realize his main bucket list item while there is still time. He has been working off and on for over 30 years to slowly build an electric car. When he attempted to power it for the first time last year the controller failed to trigger the contactors to send power to the motor. He said all he wants to do is to drive this car at least once before he dies. He gets up every day and puts on his union machinist suit and goes to work in a construction company warehouse in Ludlow Massachusetts doing maintenance and machinery repair. He has started talking about retiring and would then need to find another location for the EV project car if it is not yet finished. So I was asked to come take a look. In my distant past I have a degree in electrical engineering and have experience with SCR controlled injection molding machines so theoretically I should technically understand all documentation and pretty much understand how things should work.

The car chassis was hand built:

Overview of controller assembly:

I had thought last year we had proven that the EV1-B controller was defective and went back last month to try to disassemble and test the controller. We repeated our original investigation, with SEAT and BRAKE switches bypassed and KEY, FWD, and ACCEL switches appropriately set there was no contactor activation. Looking more carefully at the documentation, I realized that I had not considered STATIC RETURN TO OFF and PULSE MONITOR TRIP requirements, and could no longer conclude I had proven the controller defective. I was confused as the exact process (see confusing manual excerpts below). Because I was not up to speed on these requirements, we called it a day and I came home to study documentation and try to figure out a way forward. An initial successful outcome would be sending power to the motors in forward or reverse in START ACCELERATION mode.

From the manuals:

The control circuit is energized by closing the Key switch, Seat switch, and moving the Forward or Reverse lever to either position and then depressing the accelerator, thus closing the Start switch. This applies power to the control card and, if the ”static return to OFF” requirement and the pulse monitor trip requirement are satisfied, turns on the PMT driver, which will close the selected directional contactor, completing the circuit to the traction motor. The directional contactor is controlled by the directional switch.
· STATIC RETURN TO OFF — this built-in feature of the control requires the operator to return the directional lever to NEUTRAL anytime he leaves the vehicle and returns. If the Seat switch or Key switch is opened, the control will shut off and cannot be restarted until the Directional switch is returned to NEUTRAL. A time delay (0.5 seconds) is built into the Seat switch input to allow momentary opening of the Seat switch. This same delay requires the Directional switch not be closed until both the Key switch and the Seat switch have been closed for 0.5 seconds.
· PULSE MONITOR TRIP — this function contains three features: The look ahead, the look again, and the automatic look again reset.
If 1 REC (the main SCR) is shorted or lA is welded. PMT will look ahead and prevent F or R from closing if either condition exists.
If 1 REC fails to commutate, or if lA power tips remain closed when they should be open, the control will open F or R contactor. PMT will then look again by testing for a fault and, if none, reclose F or R. If the fault still exists, the F or R will reopen and remain open.
If lA closes before a second commutation failure, the look again counter will automatically reset. This eliminates the inconvenience of resetting the PMT with the key switch if the tripping is due to random noise.
When the PMT circuit prevents F or R from closing, the PMT circuit can be reset only by opening the Key switch.

I have uploaded various relevant files from various sources to my web domain in directory where they can be viewed or downloaded:

EV-1 Spec1.jpeg 1st page original EV-1 controller spec sheet
EV-1 Spec2.jpeg 2nd page original EV-1 controller spec sheet
EV1.pdf EV-1B Troubleshooting Manual & Parts Lists
EV1WireDiagram2.docx EV-1B Wiring Diagram as Word Document
EV1WireDiagram2pdf.pdf EV-1B Wiring Diagram as PDF Document
EV1closeup0485.JPG EV-1B close-up view
EV1fullview0483.JPG EV-1B full view
carfront0491.JPG front view car chassis
carside0490.JPG side view car chassis
ev1maint1.pdf GE EV-1 Troubleshooting/Repair Manual part 1
ev1maint2.pdf GE EV-1 Troubleshooting/Repair Manual part 2
ge_ev1_rs_notes.pdf Roger Stockton’s EV-1 SCR DC Motor Notes
ge_ev1_rs_notes.docx Roger Stockton’s EV-1 SCR Notes (edited)

Before our next trip to Ludlow to further evaluate the EV1-B, I have some questions:

Is there anyone familiar with the GE EV1-B controller willing to talk to me on the phone and/or correspond by email and/or make a visit to see the car to render technical assistance? All reasonable expenses would be covered. Also Facetime video call assistance is an option.

Is there a way satisfy/bypass/eliminate the PMT requirement to rule that out as a problem? I have trouble figuring how to understand its function.

If we prove a failure of the EV1-B controller does anyone have experience working on this unit?

If demonstrated defective, are there repair options available sufficiently local to Ludlow Massachusetts that can visit the site or are there sites we can bring or ship the EV1-B controller? A typical forklift repair technician may simply want to replace the EV1-B unit and not troubleshoot faults inside the unit.

Is there a source for spare parts/technical support for the EV1-B controller if we get inside the box?

Thanks in advance for help, if fortunate to succeed there will be a YouTube video of a successful outcome. This email will be cross posted at and

Paul Traceski

I hope you read this even though it is an old thread , but I blew up your controller picture to see if I could check the wiring connections and....

...your 1A contactor is welded.

It's the large relay/contactor in the bottom right of the picture.

The controller will not close a directional contactor until it sees that thing open.( It's failing the "Look Ahead Test")

· Registered
99 Posts
Many fork trucks run 50/50 forward/reverse so I don't think there is functional difference. I'd relabel the switch and try it. Rewire if necessary.


The EV1 card doesn't even monitor which direction you are going.
Direction control is done externally , all the EV1 does is turn on a driver (labeled "PMTD") that allows the direction contactors to close.

You have full speed in both directions.
( Something you need to remember when backing up )
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