CA77 Starter relay

[Nick]

Anyone ever rebuild one? Mine still makes the requisite clicking sound when power is applied, but it hasn't been used in anger in at least 15 years.

[Tim Allman]

I've rebuilt a few CB77 relays but have no experience with CA77s but I suspect they are either similar or identical. Here are a few comments.

First, is your battery in good condition and charged? This is a requirement for the starter to work. If you need to, a 12V car battery or portable jumper will work. If the starter works the all you need to deal with is the battery.

Otherwise,

Remove the large cables from the relay.
Remove the small screws on the cover and remove the cap from the body. The fact that you are hearing the clicking tells me that the magnetic coil in the main body is fine so you don't need to do anything with it.
You can see the two contacts on the inside of the cap and the copper bar that closes the contact to run the starter.
Both contacts and the bar probably all need cleaning. Steel wool works well.
If you remove the two contacts be sure to keep track of the order of the steel and fibre washers so that they can be reinstalled properly.
Reassemble after cleaning.

Otherwise,

If this doesn't work then you may have a starter motor problem, either at the terminal where the cable connects or inside but I think that is less likely.

Good luck.

[Muddy]

I agree with Tim. Address the battery first - make sure it is fully charged and reliable. As Tim suggested, use an alternate known-good battery as a check.

It could be the starter relay, but more likely the battery.