Electrical Problems Arrgh

[Ngtflyr]

Wondering if anyone has ran into this problem. 69 Z28, having an issue with the turnsignal fuse blowing. Only happens if the radio fuse is in (the one above the turnsignal fuse). With the radio fuse out, the turn signals operate normally, the 4 way flashers are on the fast side. I plan to replace the flasher and see if that fixes that issue (the fast 4 way flash). The one that has me perplexed is why does the fuse blow only when the other fuse from a totally seperate system is in. Additional info: The dash wire harness, the fuse box, and the engine bay wire harness are all repro, the intermediary and trunk wire harnesses are original. thanks in advance

[njsteve]

Those cars are very sensitive to improper grounding. If you don't have the harnesses and the firewall to engine and radiator support to fenders grounded properly, the voltage will back feed into your harness and find another way to ground. That other way can be through other live circuits.

I found this out the hard way when I ended up frying my distributor points and block temp sender because I didn't have the engine to firewall, radiator support to subframe and engine to frame grounds hooked up.

You did mention that it is the neighboring fuse that is blowing so it might be feeding back through the nearest fused circuit. Check to see that you have your front fenders/radiator support grounded properly, and the dash ground wires hooked up.

[Ngtflyr]

Thanks Steve, I have been going thru all the grounds. That is usually the first place I go to when troubleshooting. I know I am missing the ground strap on the front passenger corner of the frame. Never was one there as far as I can determine. Also one of my firewall strap screw holes wallowed out and probably not making a good ground. thanks again

[Salvatore]

I also do NOT have a passenger side ground strap from frame to inner fender well. Never did. I have an early car maybe they came later? Kinda always wondered about that.

[William]

I believe early [maybe all] '69s had a ground strap as part of the steering coupler. Easy to leave off.

[elonblock]

Also make sure that the holes where the fastener attaches to the sheet metal are bare metal and have a good bite. And doesn't have a thin coating of paint insulating the grounding fastener.

This is critical especially if the car was touched up or restored in the engine bay with fresh paint.

It only takes a thin coating to insulate the fastener and seek a ground elsewhere as was mentioned previously.

I ended up welding up the holes in the firewall and redrilling, because the holes were oversized and the screws were basically a slip fit.

It can be a real hair puller!

[Ngtflyr]

I will be rechecking all the engine ground straps, and will be adding the ground strap to the passenger side frame to inner fender well. Looked at another car today that has one there. My car definitely never had one in that location but will tomorrow. All the ground straps are well illustrated on page 439 of the assembly manual as well. I will let you know if those fixes solve this PITA.