Dielectric grease on starter switch contacts

M

mcgarrett

Well-known member
Had a recent problem with the contacts sticking closed on my starter switch and, you can guess how that went. Wondered if applying some dielectric grease on the contact points of the switch would prevent arcing/welding of the contacts and avoid an instant replay when I least expect it.

Just like my starter motor, let the comments run wild! :rolleyes:
 
Yes it helps. Doesn't take much. Some will argue that the contacts get hot enough to cause the dielectric grease to make a mess. That has not been my experience.

Make sure the switch is in good shape and that the moveable contact has enough spring force. Some aftermarket switches have a weak spring force.
 
I took the switch apart to confirm arcing, pitting, burnt spots, but no other mechanical problems have been identified. The switch is not one of the cheap imports, it is a quality US made switch with the berryllium copper spring strip. After looking at the CRC product usage description on the label, I think I'll give it a try. If it doesn't work as advertised, it can easily be removed without doing any harm to the switch.

Here is a quote about the product on Amazon:
SEALS AND PROTECTS: Seals; protects and insulates electrical contacts while reducing arching and voltage.
KEEPS ELECTRICAL CURRENTS SAFE: Prevents corrosion by repelling moisture; dirt and oils that can penetrate and harm electrical connections.
EASY TO USE:Precision Tip Applicator applies a thin stream of grease directly on the work area.
MULTIPLE APPLICATIONS: Electrical panels; outdoor lighting; scoreboards; traffic lights; high voltage poles; transformers; disconnects; switching mechanisms; electrical contacts; spark plugs; battery terminals; and fasteners.
 
Good tip - I will dress the rough spots down with some emery cloth before applying the dielectric grease. Thanks.
 
mcgarrett said:
Good tip - I will dress the rough spots down with some emery cloth before applying the dielectric grease. Thanks.
Click to expand...

IMO, you need to take care doing that to keep the contact area square so that you aren't actually reducing the contact area and causing more arcing.
 
This slide may help you. I would avoid using grease.
 

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Thanks to all for your comments.

BobB - I am using the good switch with the strong spring. I won't be using a file to smooth the rough areas where the arcing is taking place; just some light sandpaper before applying the dielectric grease.
 
Mc, May I pile on ?? Your focus is too narrow.

- If you are standing on that starter switch to start your car instead of tapping the starter, something is wrong. I'd start by cleaning all the battery cables, especially the ground to frame connection. The mounting surface between the starter body to clutch housing needs to clean as well.

- Check your basic timing and carb settings.

The overheating/welding of the starter switch contacts usually a result of hard starting.
 
The use of dielectric grease was more in tune with plug type connectors that have tight fitting male & female pin & socket type connections. This insures that moisture stays out of the connections. I also used the stuff for high tension lead terminals on magnetos. This has the added affect of preventing cross arcing of these type terminals. The silicon greases such as DC4 will melt easily if they get hot so spark plug terminals have to remain clean and dry but it stays in the distributor sockets of the mags.

Switches have to be clean to function well. If a person looks at the electrical contacts on an aircraft quality start relay, they will have silver contacts since it's harder than copper alloys and it a better conductor. Platinum would be better but even more expensive. The copper alloy contacts should be cleaned if the switch takes higher than normal tension on the pedal to function. A person shouldn't operate a starter more than 30 seconds. It should be allowed to cool at least one minute after a lengthy operation. Keeping the engine in good working order will negate the need for lengthy starter operations.
 
Engine is in good tune - as soon as it gets fuel it starts right up cold or hot, so that's not an issue. Just took a second or two for the switch contacts to stick. I was speculating that the dielectric grease might be a good preventive maintenance measure. I'm going with it.
 
It is a dielectric so it doesn't conduct electricity. A solid contact between switch contacts will push the stuff out of the way so it won't have any more than a very thin film after a few initial contacts. The grease won't hurt any thing but it may require a bit more pressure or tension on the pedal for the first few starts. As I mentioned before, if the terminals get hot, the grease will melt off the contact surfaces. It will not prevent arcing. High current load contactors are going to arc now and then and nothing will stop that. The construction of the housing will generally keep a lot of dust from getting inside there but it depends on conditions. In a very dusty environment with no engine pans, it will get in there and stick to the grease so it may get a build up of crud around the edges of the contacts over time.
 
I do have engine pans and a good gasket between the switch and the starter motor, so should be good for a while at least to see how effective it is.
 
devoreb,
Thanks for chiming in with your personal experience on this topic. If used in moderation, I don't see any downside.
 
I had the same problem with sticking switch a number of years ago. No fun. I took the switch apart and filed down the pitting, and used dielectric grease on the surfaces. I drove it for several more years without a problem. (I later sold the car.)
 
A electrically conductive grease ( do a Internet search ) would be a better choice! If your contacts are sticking check and makes sure the contact patch is 100%
 
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