Another Blown Controller

[ta69man]

Hi All,

So I've posted a few times... but a little histroy... I purchased a 2006 precedent for a "good" price. It had a burned up controller in it. I got a used controller from a local golf cart place and put it in and nothing... ended up being bad. I got another on exchange, this time they said they tested the controller. I put this one in and I got a little more action. The reverse beeper would at least come on with reverse selected... although I noticed there was no solenoid closing and the precharge resistor was getting hot. I check voltage at the battery + on the controller and it's 0 volts. Something is holding this to ground and not allowing the caps to charge up. I removed the M+ motor wire just to see if this changed anything... no change. I went back to the motor to look for continuity between armature and field.... AH HA... I see that the F and A terminals have 0 ohms between... but this is with the controller still connected to the F terminals. I disconnect the field wires and check again but now there is no continuity.... So I think there is continuity in the controller from the factory and move on. I now connect the battery pack back up and look for voltage at the B+ on the controller thinking that everything is disconnected from the motor and thus there is nothing left to draw the power down... Well I STILL only have 0 volts on B+.... but for giggles I throw the Tow/Run switch to run (planning to key on and see if now the solenoid closes) but once I hit the run position I hear the sound of FETs dieing inside the controller... I have no idea how but I just blew this one with the motor wire and the field wires disconnected... Though NOW I am getting 48 volts on the B+ terminal. I removed the controller cover to find a FET or two who let the smoke out...

So question is... Has anyone seen this before? Motor connection and both field wires disconnected causes controller to fry? Do you think it was something I did or another bad controller? The motor tests ok but I don't want to just throw another controller in the mix to find out. I did run the motor directly off of power supplies (for a short time) and that went ok.

Thanks...

[ta69man]

Another note... I took a closer look at the old controller and am now thinking this cart was involved in a flood. I can see some water lines on the inside of the original controllers case now that I've pried it apart. The cart is also hard to push like the brakes are dragging. This doesn't explain why the newer controller blew with no motor connected but might add some things for me to look for on my quest to get it running...

[Nsane]

If that's the case, I would replace All electrical components, water is a evil thing on electrical components.

[Gregorio]

If the motor was eliminated from the mix, what other components are there to replace besides the MCOR and solenoid?

OP are you sure that you eliminated the motor as a problem? You disconnect it after powering up the last controller, no? The damage could have already been done.

[Nsane]

Solenoid, motor, controller, MCOR, fuses, batteries, anything that has been under water.

[ta69man]

So, I drained the axle and found good used oil (no water) so that was a positive. I looked around the cart some more and found more water lines on the inside of the body. Looks like it got right up to the axle vent but stopped there... lucky. I imagine the dragging brake feel really is the brakes if they got water logged. I'm gonna go ahead and pull the axle and motor apart to make sure everything is ok.

Gergorio - Yes, I had the motor completely disconnected when the FETs died. I had just disconnected it and when I switched from tow back to run is when I heard the fireworks inside.

I opened up the controller and dismantled it. Two of the four FETs involved in the field outputs popped. Nothing else looks hurt so I'm gonna get some new FETs and pop them in (all new ones for the field circuit) and see if I can get this controller running again...

If you have seen a controller pop with no field connections please let me know as this is a mystery to me! When I fire it up again this time I'm gonna put a small fuse in line to make sure that dies first if issues are still there.

[NoleFan4Ever]

If there were no field connections and it still popped, I would think it could only be an internal ground at the controller. You may want to look deeper into the controller circuitry as something is strange....

[Gregorio]

Originally Posted by NoleFan4Ever

If there were no field connections and it still popped, I would think it could only be an internal ground at the controller. You may want to look deeper into the controller circuitry as something is strange....

Yeah, I was actually hoping it was the motor. That would have been easy.

[NoleFan4Ever]

Originally Posted by Gregorio

Yeah, I was actually hoping it was the motor. That would have been easy.

agreed