Burned ECU board pics-4110

[al3]

Tractor had a 10+ y.o. Optima battery; went to start one morning it cranked once or twice then just a buzzing relay----so I jumped the battery with a spare 12 V marine battery. Was cleaning up some cut trees, after 30 min or so I smelled something like burning brake pads. About 10 min later the tractor just stops. (Fuel solenoid shut off) No crank, no battery power whatsoever.
After a replacement battery was installed, tractor wouldn’t start reliably. Troubleshot and found voltage to fuel solenoid pull in coil wasn’t reliable. After verifying all the various safety/charging related circuits, I pulled the control box apart to find the over-temped resistors. Could be just coincidence but a review of TBN posts has a curious number of control box popping up at the same time as failing batteries.

I did pull out the multi meter and checked all the resistors, diodes and traces. Also re-soldered where there were suspect joints. Boards continued to work intermittently. Issue is a circuit that provides 12V for one second; it works sometimes but not always. I’ve reached the limit of my electronic trouble shooting knowledge.
Been looking at the wiring schematic and pondering bypassing the control box altogether. Basically eliminate all the various interlocks, wiring the various relay switch coils through either the run or the start positions of the key switch. Still need to evaluate a a few circuits (like the reverse polarity safety set-up) before I try.

 

[k0ua]

The dead battery is not what killed the semiconductor or other components on the board. Jump starting and its associated voltage spikes is what did the damage. There are always risks in jumpstarting any vehicle electrical system. Proper connect and disconnect procedure can mitigate that risk, but there is always some risks of damaging electronic devices. That and exploding batteries is why I do not like to JumpStart vehicles unless I have to.

 

[al3]

Certainly could be the results of the jump; I wouldn’t rule out anything having to do with the circumstances of attempting to operate with a low battery. Damage to board indicates excessive heat caused by something---
I’m game to running down individual components, need to check transistors next. Any hints on identifying transistors types? (NPN , PNP, etc) Any other tips would be appreciated. I’m armed only with some better quality old school analog multi meters as my digital display model decided to become erratic.
I used to live South of Virginia MN and North of Duluth, but one too many 130in plus snowfall winters and minus 30 degree days resulted in a move to a place where I can once again grow tomatoes......

 

[jix]

Just do not try to test any semiconductor with an analog-type ohm meter. The analog meter battery will easily fry delicate electronics. Use only a good digital meter. Even then you could destroy some semiconductors. They best way is with a digital oscilloscope, but these are rare and require a lot of knowledge to use properly. As a Radar tech, I do know that this if the truth.

 

[tcartwri]

The board looks like a voltage / charge regulator. And personally I would suspect the Optima battery internal resistance being too far from spec.

 

[jix]

I looked closely at the burned cct board.. It seems that there was a cascade of fialures involved. Maybe the first component to go was a Zener Diode which is often used to clamp a voltage at a certain level, to protect a transistor from overconducting, which it did. Tht burned out the control resistor and threw the control votages all over the board way off.. that fried all the rest of the board. I agree that this was a consequence of jumpering the battery improperly. This board could probably be repaired by a good technician with a lot of patience..if the details of the comp[onents can be determined I would estimate about 40 labor hours and three hundred dollars worth of components, if you feel lucky.
I would scrap it and buy a new battery, being really **** in the future with battery swaps, etc.

Good Luck.. PS: I have the same worry about the ECU in my tier4 kioti, in the far distant future. Sign of the times, I guess. I will buy a spare ECU and carefully mothball it. NO ECU, no tractor either.

JIX

 

[al3]

To answer various questions:
The purpose of this board is to integrate various safety switches (seat, PTO, neutral positions) and either supply or deny 12 volts to a fuel shut off solenoid. There is a separate voltage regulator elsewhere.
Didn’t know the low DC voltage (either 9VDC or 1.5VDC) of the ohm meter could damage the simple 3 legged transistors populating the board and designed to have 12VDC pass through them. I’d always thought of these functioning as back-to-back diodes, allowing one way current flow
The theory of operating part of the shop manual says the circuit that’s behaving sporadically (provides 12v for 1 second to a solenoid coil) does so by providing a path to ground for one second. Any ideas on what component to look for that would perform this task?
In many ways the best case cause would be my jumping the battery. That way I’d know the cause of the failure. I tested all other circuits with the exception of the regulated amperage as I don’t have a reliable amp meter---suppose to be 13. 5amp min per the shop manual.
And I have to add, I’m pushing 60, must have jumped dozens of cars, tractors, and trucks over the years. This is the first one that damaged anything. This is also the first gas-matte battery I’ve run to zero.
Thanks for everyone’s ideas.

 

[Mysfyt]

Burned out a board on an electric forklift by running it on too low of a voltage. Remember, as the voltage drops the amperage goes up. Amperage = heat.

 

[jix]

A13...Just a wild guess, following your last post--Have you checked to see if the fuel soloeno0id coil is shorted?
Jix

 

[k0ua]

We need to see the schematic for the board. The large transistor in the TO-220 package could be a solenoid driver. I spied the little zener diode. That would be a good check. But a lot of shooting in the dark without the schematic. Transistors are not really back to back diodes, think of them a lot like triode vacuum tubes. With three elements, emitter base and collector roughly corisponding to cathode, grid and plate. If that helps any.