View Full Version : How To: New Relay ground buss

08-14-2013, 07:32 AM
The grounds on the relays are really turning out to be a problem area. My car had a bad ground on the fan relay but it did not show up as a problem. I just found it by accident when I was measuring a ground resistance for some other reason. But many people installing my fan relay, fan fail unit and dome light unit are finding bad grounds also.

The problem seems to be the use of crimping two wires into each relay pin. This is allowed by the pin manufacture but seems to be a problem with the 30 year age of these connections.

I inspected the crimps on my bad (high resistance) connections when I pulled out the pins and did not see any defects with the crimp. But when I pulled the pin the connection now tested good (low resistance).

So what I did was crimp a new pin and new wire (16 AWG) for each relay ground. Note that some relays also grounded the center pin which I eliminated that unused pin. I then joined the ends of all those “front bank” pins to one 16 AWG wire which got spliced into the existing ground wire that was running back to the common ground point back in the rear of the relay compartment. You don’t need a heavy ground wire for the relays since there are no large ground currents. I like to use un-insulated butt connections so I can crimp and inspect. I also solder fill the crimp and heat shrink over it. You can run the butt connections into both ends (remember to add the new ground wire) so you get a good crimp on a butt connector rated for 8 AWG wire.

Here is a photo of the back relay butt connection. The back bank has three ground wires (three relay pins) and also shares one of the AUX relay ground pins. So what I did was butt connect the three relay grounds on one end, and two new ground wires on the other end. Then I spliced those new ground wires to the aux relay ground and to the original ground wire going back to the soldered group in the back of the relay compartment. Wish I had documented the front relay bank when I did it a few years ago.

The way to make a new harness is to build it on the bench. That way you have all the new wires butt connected, soldered and heat shrunk. You can then cut each wire to length and crimp the new relay terminals on the bench or in the car. Doing the butt connector in the car is hard to keep all the wire into the connector when you need to crimp them. Hopefully someone will add their photos of the front bank upgrade to this how to guide.

Some vender should make up a set of these new ground wires to sell as an upgrade

Maybe someone could also try soldering the existing ground harness. I would think if you dipped each pin in TARNEX you may be able to get a good solder joint on that old copper wire. Of course you need to completely rinse out the TARNEX with many dips in solvent.

08-14-2013, 08:56 AM
Being a new owner, I am getting ready to dive into the fuse/relay area very soon.