99 dcs runs now but burns diode/resistor

[Jonny Club Car]

So we have a 99 ezgo txt that has everyone at the shop puzzled. It had a bad reed switch but before the inexperienced tech figured that out it received a new solenoid because he claims that he was able to measure 24v + on the metal case of the solenoid. After the reed switch was replaced all the systems powered on and the cart would move an inch but the controller pre charge resistor was bad or so I thought. We ordered 28336-G01 resistor/diode boards and replaced the resistor/diode. The cart drove great but we noticed a burning smell and found that the diodes had burnt on the board. So the cart is still running but the part that fixed it has failed because the diodes have split and burnt. Obviously the diodes shouldn't be blowing but the resistor is needed to get the cart to drive. What should I look for to keep these diodes from burning?

[JohnnieB]

Originally Posted by Jonny Club Car

So we have a 99 ezgo txt that has everyone at the shop puzzled. It had a bad reed switch but before the inexperienced tech figured that out it received a new solenoid because he claims that he was able to measure 24v + on the metal case of the solenoid. After the reed switch was replaced all the systems powered on and the cart would move an inch but the controller pre charge resistor was bad or so I thought. We ordered 28336-G01 resistor/diode boards and replaced the resistor/diode. The cart drove great but we noticed a burning smell and found that the diodes had burnt on the board. So the cart is still running but the part that fixed it has failed because the diodes have split and burnt. Obviously the diodes shouldn't be blowing but the resistor is needed to get the cart to drive. What should I look for to keep these diodes from burning?

Neither the resistor nor the diodes are needed for cart to drive, the are protective devises.

The resistor keeps the filter capacitors in the controller charge near to battery pack voltage, reducing the amps inrush when solenoid contacts close. The solenoid contacts bounce several times upon closure and keeping the filter capacitors charged reduces arcing during the bouncing, extending the lifespan of the solenoid's contacts.

The diodes prevent the controller from being overvolted if the solenoid contacts open during Regen braking. When acting as a generator (Regen braking), the motor's output voltage skyrockets when unloaded, the diodes keep the output connected to the battery pack, limiting the voltage felt by the controller to a safe range. The banded end of the diodes should be connected to the solenoid's battery side large terminal.

If the diode are burning out, the resistor/diode kluge might be installed backwards.

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If the resistor is getting hot, make sure the solenoid contacts are good. IE: 0V drop between large terminals when solenoid is energized.

[Jonny Club Car]

After more testing I have found that the solenoid isn't closing and the resistor is burning up because it is the only way I am able to drive power around the open solenoid is through the diodes and resistor. I have checked the f/r micros they are good. The micro near the accelerator is working properly.

[Jonny Club Car]

I'm getting 36v + on both sides of the small posts of the solenoid. When I place the black probe on the bl- and the red probe on the small post with the blue wire I read 36v this should be the negative correct? When I place the black probe on the bl- and the red probe on the small post with the red, yellow, and white wires on it I read 36v as it should. I have checked all of the wires between the switches and solenoid and everything is connected as it should be far as I can tell.

[JohnnieB]

Originally Posted by Jonny Club Car

1. I'm getting 36v + on both sides of the small posts of the solenoid.

2. When I place the black probe on the bl- and the red probe on the small post with the blue wire I read 36v this should be the negative correct?

3. When I place the black probe on the bl- and the red probe on the small post with the red, yellow, and white wires on it I read 36v as it should.

4. I have checked all of the wires between the switches and solenoid and everything is connected as it should be far as I can tell.

1. This tells us the solenoid coil is intact.

2. BL- (which is leftover from the Marathon days when the batter pack was split into two halves, one on each side of the cart and is the same as B-) is the most negative point of the entire electrical circuit, so the most negative voltage that can possibly be measured is Zero Volts.

3. That means the solenoid activation circuit external to the controller is intact.

4. Is the battery pack voltage applied to Pin-5 when pedal is pushed. If so, the controller is bad.

In a nutshell, the controller supplies B- to the solenoid coil via the blue wire from a relay driver circuit that is triggered when 36V is applied to Pin-5 by the pedal switch. That isn't happening, so the controller is bad.

FWIW: The stock DCS controller (Curtis 1206SX) is a defective design, so replacing it with a new, rebuilt or repaired 1206SX is throwing good money after bad. Replace it with an Alltrax XCT48400-DCS and solve the problem once and for all.