I'm reinstalling the dash, and checking wiring, connections, etc. I was not getting power to the ACC or IG busses in the fuse panel. I could hear the ignition relay 'click' with the key in the Acc or ON positions, and I could see power from the fusible link getting to the white-red wire at the bottom of the C6 connector. I pulled the dash back enough to back-probe the ignition relay connector, and confirmed that voltage was getting to the ACC and IGN contacts, but was not passing through when the relays were energized.

I removed the ignition relay, and further confirmed by testing that both relays would click, but would not pass power through their contacts.

This forum says the relay is not easily replaced, so I thought I would dig deeper.

Start by bending back the cover tabs (circled), but try to be careful of the ground tab (arrow):

 Open the relay while trying the use the ground tab as a 'hinge':

Admittedly, these relays appear to be in sad shape. But further examination showed that the contacts (circled) were actually in excellent condition, but there was a buildup of rust and crud between the coils and armatures (arrow):

Note that by this time, I had broken the ground tab (square), which appears to have been spot-welded to the relay case.

Clean up the crud with a folded over piece of 1000-grit:

Retest both relays to make certain they are really snapping closed and making good contact.

Put the relays back into the cover, and re-crimp the tabs to hold it together.

If you broke the ground tab, solder a pigtail to the tab.

Note that I tried, but could not reliably solder the tab back to the cover where it had originally been welded.

When reinstalling the relay, be sure to put the existing ground wire under the relay mounting tab, and then you can put your pigtail ground under the same mounting bolt on top of the relay mounting tab.

If the contacts had not been in good condition, I would not have done this, but would have instead resorted to wiring in new relays,

 

 

Edited May 29, 20213 yr by Roberts280Z
remove extra pic

What methods/materials did you use in your attempts to resolder the connection?

I'm assuming the strap is copper and the steel cover had been tinned?

2 hours ago, Roberts280Z said:

If the contacts had not been in good condition, I would not have done this, but would have instead resorted to wiring in new relays,

Not me... I would have wired in new relays. I've been beat down working on the electrical of these old Datsuns and now I replace rather than mess with the 40+ year old electrical stuff for the most part.

ETI4K - the cover didn't look like it had been tinned. I just tried plain old soldering, but even when it looked like I had a join to the cover, it popped off easily.

cgsheen1 - I'm getting to that beat-down state, can't get the turn or hazard signals working now, I'm working through it one circuit at a time.

If you ever try it again, wire wheel/brush the steel until brilliantly clean, then use either solid solder with acid flux or acid core solder.  The absolute key is to be clean.