On a recent C5 restoration I did, it had a faulty Control Box and, after lots of testing, I found out diode D1 was bad, the Relay was damaged, the LM358 was fried (IC2) so set about finding replacements (ebay) for it:


Relay 12V 70Amp


LM358


Diode D1

Here is the control box with everything swapped out and tested, with the original broken Red relay on the left:



All back together:



Whenever replacing IC2, the LM358 chip, it's worth putting in a socket first, and then plug the chip into that.  Makes it easier in the future if the chip blows again
There you have it, another fixed control box