I'd like to get suggestions on the best way to clean electrical terminals and connections on older locomotives. I have been working on a number of older GE industrial locomotives and the connections to resistor panels, individual resistors, contactor terminals, etc. are in many cases very corroded or questionable. There is also the issue with the classic GE variable resistors where you slide a band up or down the outside of the resistor to adjust the resistance value. These get very dirty and/or corroded, so may cause issues on the resistance value if you try to change it. Even just trying to get a resistance value can be tough when you are dealing with old, weathered/corroded terminals on the resistors.

What is the best way to clean up these terminals and resistors? Is there actually a spray cleaner that will clean off the top corrosion layer to get down to a good metal connection? I know that there are different electrical parts cleaners, but I'm not sure how well they would work for the corrosion buildup on 60+ year old locomotive parts, or the corrosion we see in the dirty locomotive environment.

What about the use of an extremely low abrasive, such as the "bright boy" type cleaning blocks commonly used to clean track in the model railroad hobby? While I know the dangers of creating micro-pits that attract dirt and corrosion, the cleaning would most commonly be between mating surfaces of the terminal and a ring-type crimp connector. So once the connection is tightened, there wouldn't be much room for dirt buildup.

Looking forward to hearing people's suggestions on this and what you have done in your maintenance or preservation efforts.

Tom Mack
Cincinnati, OH

You can get electrical contact cleaner in spray cans at any auto parts store. It works pretty good, but it ain't cheap, and the fumes will kill you.

Be very careful around those ceramic resistors. They crumble easily if they are original to the locomotive. Once that happens, they act like a "slinky toy". Carefully check the connections for resistance and if none is found leave well enough alone. Don't try to clean them with anything other than a spray like Sammy suggested. Sliding the adjustable band to change the resistance values may wreck the resistor and may not be worth the effort if the values aren't way out. 50 years ago, GE still had new ones, but that was a long time ago now. I had to replace about 4 of them in a bank on a 44 Tonner. IIRC, the replacements were quite pricey.

CAIG offers their line of DeoxiT products which are some of the best, whether just cleaning or cleaning and lubricating. I use it on switches, potentiometers and rheostats with excellent results.
https://caig.com/

Upvote on DeoxiIT D Series. Used it on guitar pots and vintage pinball machine connectors & switches. Good stuff though a bit more $$ than regular contact cleaner. Was recommended by a guitar repair shop.

They also have a protectant for after you clean contacts. S Series, I think. Haven't used it so can't say one way or the other.

In my experience those contact cleaners are useless in the railroad environment. I've had some success with Deoxit for low-voltage interlocks but you have to get the heavy dirt off first. 400 grit sandpaper.

Another thing to keep in mind: the outside of the connection might look terrible, but the actual mating surfaces are just fine. I've never seen a bolted connection go bad just sitting there, as long as it remained tight. This includes connections which went underwater. On the other hand, if the connection is loose, corrosion can set in between the mating surfaces. Likewise, the instant you take it apart, you must commit to cleaning everything thoroughly before re-assembly.

Those adjustable resistors with the clamp band are a failure waiting to happen. Leave them alone! Once you loosen the clamp and disturb the spot where it had been sitting all those years, it will be very difficult to get a clean connection someplace else. You can try light abrasive cleaning but the resistance wire is very brittle. These also tend to fail when the clamp is just slightly loose and the connection starts vibrating.

They make packs of small stainless brushes that work well in a small drill or dremel type tool, they will polish connections nicely and even won't strip your flesh off instantly with incidental contact.
https://www.harborfreight.com/5-piece-stainless-steel-wheel-and-brush-set-66129.html
The larger ones are better for the bulk of the work and the small ones get into the barrier blocks and others nicely.

I would use these on the wirewound ceramic resistors without much fear, with a light touch. If the resistor is that bad, it needs replaced. That kind of resistor is still commonly available, and you can also substitute other kinds of power resistors or combinations in a pinch.