ground problems
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
On some yrs, one grd cable comes outside of the bottom of the battery box and down to the frame.
Another is from the passenger side of the block, near the starter, to the frame, near the idler arm.
A super good ground is imperative on C3s. Grounding bolts must be shiny clean as are the terminal ends of the cable and the frame mount location itself. Like they say; 90% of electrical issues on C3s are poor GRDS.
Another is from the passenger side of the block, near the starter, to the frame, near the idler arm.
A super good ground is imperative on C3s. Grounding bolts must be shiny clean as are the terminal ends of the cable and the frame mount location itself. Like they say; 90% of electrical issues on C3s are poor GRDS.
Last edited by HeadsU.P.; Dec 6, 2018 at 09:35 AM.
Racer
Joined: Jul 2007
Posts: 397
Likes: 77
From: Jasper, GA
I think most of these are applicable to your '74:
- drivers side #1 mount to frame
- driver side on frame rail (just in front of gas tank) ground wire (16g blk) from rear harness + ground wire coming from led fog light
- rear light harness - rear crossmember
- at least one in the instrument panel i think it was by the headlight switch
- ground strap at the #4 mount on the driver's side
- rear area behind the bumpers in the middle of the frame connector above the spare tire carrier
- passenger side "engine" mount to frame
- Above the horn and vac relays for the headlights (near the tip of the hood you can see the radiator support brace) ground cable from front wire harness + ground cable from lamp harness
- antenna mounting plate to the frame
- battery to frame behind drivers seat (there is a star washer underneath the eye connection, diff. crossmember)
- left front hinge pillar
- on tranny case coming from the starter wiring loom
- ground to gas sender unit (18g blk)
Richard
- drivers side #1 mount to frame
- driver side on frame rail (just in front of gas tank) ground wire (16g blk) from rear harness + ground wire coming from led fog light
- rear light harness - rear crossmember
- at least one in the instrument panel i think it was by the headlight switch
- ground strap at the #4 mount on the driver's side
- rear area behind the bumpers in the middle of the frame connector above the spare tire carrier
- passenger side "engine" mount to frame
- Above the horn and vac relays for the headlights (near the tip of the hood you can see the radiator support brace) ground cable from front wire harness + ground cable from lamp harness
- antenna mounting plate to the frame
- battery to frame behind drivers seat (there is a star washer underneath the eye connection, diff. crossmember)
- left front hinge pillar
- on tranny case coming from the starter wiring loom
- ground to gas sender unit (18g blk)
Richard
Last edited by lakerider57; Dec 6, 2018 at 12:19 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
Just think of this car as a boat. every single thing that is not mounted to metal has to be grounded separately. All the lights that are in the fiberglass body have to have a ground wire run to the frame. Or into a ground in the harness. And then you need the really big ground for the starter amps. I don't feel that **** go from the engine to the frame and the frame to the battery that's four separate points of possible loss of ground path. You should run a separate ground from the negative of the battery terminal to the engine block itself.
Last edited by derekderek; Dec 6, 2018 at 11:53 AM.
Melting Slicks
Joined: Mar 2005
Posts: 2,095
Likes: 299
From: Midlothian VA
The blower motor and wiper motor are grounded via a ground wire that runs along the firewall harness and connects/grounds to the large retaining bolt at the starter.
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Melting Slicks
Joined: May 2015
Posts: 2,365
Likes: 428
From: Cape Girardeau Missouri
And yes, the strange things happening when you turn on the headlights brings high suspicion on the front lamp harness grounds. I was able to access the one on the driver lower radiator support by removing the driver turn signal and using a wild combination of universal joints (2 of them), wobble extension and regular extensions. It also took a helper with reasonably small hands to guide the socket onto the bolt head. The bolt head is reasonably easy to see it's just a royal pain to get any tool on it.
