Dielectric Grease?

[Dzimm]

I want to confirm the bulkhead plug for the underdash fusebox is filled with dielectric grease correct?  I don't have any problems with it I just had to remove it to get the parking brake out and wanted to confirm before reassembly.

[Minuit]

Yes, and most likely as a simple waterproofing measure. It'll work just fine without any grease, and it's probably a good idea to clean that off anyway. The grease's only purpose is to prevent water from corroding the contacts and keep it from passing through the connector to get inside the cab... since they decided to use an UNSEALED connector on a friggin' bulkhead...

[Dzimm]

Thanks!  I'll probably wipe down some of the excess, not sure I want to spend the time required to clean it out entirely if I don't have to.  I'm not flexible enough to stay contorted under the dash for very long.

 

[Ωhm]

The grease in dialectical grease also helps when multiple terminals are mated together within a single connector.

[AZJeff]

Dielectric grease also has another function, one that is common to many low-current or low voltage connections:  it prevents "fretting corrosion".   This type of corrosion can happen on almost any connector that does not have silver or gold or platinum plating on the contact points (fat chance of that on most auto connectors.)

 

The grease seals out oxygen at the interface point between the two contact surfaces (at the almost microscopic level) and prevents increase in impedance (resistance) across the joint over time.  

 

Lots of different greases will work, as long as they do NOT have any metallic components in them (like molybdenum, lithium, or such).   Silicone greases are the most common dielectric type, but polyethylene greases work well, too.