Resistor speed switch board...sizzled

[TennBill]

89 Marathon. Hopped in today to head to the garage, 300'or so. Seemed strange, no low speed, floored it and took off. Got in the garage and smelled terrible, plastic burning odor. The top, no. 4, wire was smoking at the connection to the resistor board. Pulled the board off and saw the contacts had what appeared to be drops of solder between the 3 top wires. I noticed too the contact arm was bent as well as the micro switch arm. I bought this used a few months ago and it has seemingly worked fine. It appears someone had pushed the contact and arm into the board and bent the micro switch arm. Therefore, it didn't trip. I'm not sure what the micro switch does......or didn't do. Hoping I haven't damaged anything else! Looks like the board and contact is about $60. Not sure if should try to clean the contacts and re-use, or replace?

[yurtle]

Originally Posted by TennBill

89 Marathon. Hopped in today to head to the garage, 300'or so. Seemed strange, no low speed, floored it and took off. Got in the garage and smelled terrible, plastic burning odor. The top, no. 4, wire was smoking at the connection to the resistor board. Pulled the board off and saw the contacts had what appeared to be drops of solder between the 3 top wires. I noticed too the contact arm was bent as well as the micro switch arm. I bought this used a few months ago and it has seemingly worked fine. It appears someone had pushed the contact and arm into the board and bent the micro switch arm. Therefore, it didn't trip. I'm not sure what the micro switch does......or didn't do. Hoping I haven't damaged anything else! Looks like the board and contact is about $60. Not sure if should try to clean the contacts and re-use, or replace?

At a quarter of a century old...

[TennBill]

Gee, that was helpful! You know for a fact it's the original board?

[yurtle]

Do whatever you want. You were asking whether you should replace them without giving us the age. I guess you already have your answer. Reuse the most critical contact in the high amperage system. Never mind they already failed. What do you think caused them to overheat and melt the plastic you described?

[yurtle]

Given the condition you described, I'd look at replacing the whole assembly, including the microswitch, rather than purchasing some parts and reusing others.

Also, inspect the condition of the cable terminals. If the contacts got hot enough to melt the board, the cables may have also been damaged.

i agree you need to look at the whole picture not just one part