1957 wiper motor and radio grounds

[Art B.]

The 1957 chassis wiring diagram does not even show the radio and wiper motor. Can someone tell me where these are grounded? I assumed they would be on the right hand valve cover bolt like my '61.

[Richard M.]

Re: 1957 wiper motor and radio grounds

Art,

1957 AIM shows wiper ground on Sec 12 Sheet 6 View C. It looks like the ground is attached to the cowl vent brace stud. Note Sec B Sheet 9 also. Sec 12 Sheet 12 shows a ground to the dash reinforcement via a bolt, so that brace stud must be grounded to the reinforcement brace mechanically.

The Radio is on Sec FOA 102 Sheet 2. It doesn't show a separate radio ground wire going anywhere. Maybe it gets ground through the L bracket to the metal brace?

Hopefully someone has more info.

Rich

[Gary C.]

Re: 1957 wiper motor and radio grounds

Wiper Motor base plate is grounded and the wiper motor case is mechanically grounded when the motor's bolted to the wiper motor base plate.

Gary
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[Art B.]

Re: 1957 wiper motor and radio grounds

Gary: How about the radio? Is there a separate ground wire connection like on later wonderbars? If so, where is it grounded?

[Gary C.]

Re: 1957 wiper motor and radio grounds

Art,

IIRC the power plug has 2 leads. One lead is battery and the other lead is ground. Don't recall an external chassis ground for either the radio or the power supply.

Didn't go to the shop to check as it's cold and rainy here today.

Gary
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[Art B.]

Re: 1957 wiper motor and radio grounds

Gary: Then the radio ground must connect to the main wiring harness via the power plug. The main harness has a ground wire that goes to the bolt on the left side valve cover. Does that sound right? The wiring diagram and AIM information does not indicate this. Thanks for your input.

Art

[Gary C.]

Re: 1957 wiper motor and radio grounds

Art,

The under dash main wiring harness ground (radio plug ground source) connects to the dash reinforcement bar.

I've never traced the ground source for the dash reinforcement bar.

Maybe Rich or someone else has.

The cowl vent is grounded to the engine valve cover volt. But don't recall the wire gauge. If that's the only ground for the dash reinforcement bar it would have to be a 14 gauge wire or better.

Gary
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[Art B.]

Re: 1957 wiper motor and radio grounds

Gary,

I hate to belabor this issue but my '57 had a previous owner that did a lot of odd things to the car. Can you tell me where, physically, the harness ground connects to the dash reinforcement bar? I got under the dash last night and cannot find any wire connection all across the reinforcement bar.

[Gary C.]

Re: 1957 wiper motor and radio grounds

Art,

AIM Section 102 sheet 2 shows the dash wiring harness connection to the dash reinforcement bar.

Gary
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Dash Bar Ground_041113.jpg

[Art B.]

Re: 1957 wiper motor and radio grounds

Gary, Thanks again. My '57 does not have this connection. The radio is getting its ground somewhere else. I will find out where.
Some of my friends would say I have too much time on my hands.

Art

[Dan D.]

Re: 1957 wiper motor and radio grounds

Art,

The radio front control shafts protrude through a metal dash reinforcement plate that ties to the lower dash right below the tachometer. Keep in mind the radio chassis, covers, and shafts are all metal and at ground potential. Instrument lights, clock, and possibly other instrument panel gauges and lights also get to ground through the lower dash reinforcement. In addition, the wiper motor has a dedicated ground wire from the motor mounting bracket to one of the cowl vent screws on the firewall. The other end of the cowl vent is tied to the lower dash reinforcement as well.

So then, how does the lower dash reinforcement get to ground? Well, it is grounded via a harness ground wire located under the headlight switch. This wire is tied to several other ground wires within the taped harness. One such ground wire picks up ground on the drivers side valve cover.

Also, the radio antenna is grounded to the frame inside the trunk. This ground is passed through the coax shield to the radio. And the radio power unit is fastened to the lower reinforcement too.

The lower reinforcement plate is raw steel and will rust without hesitation, which puts all ground connections at risk.

In general, the grounding design in these cars horrible, and that is being polite. Someday I am going to pen a paper detailing out the ground system employed in C1s.

Hope this helps,
-Dan-

[Art B.]

Re: 1957 wiper motor and radio grounds

Dan, Yes, an article on the '57 ground system would be very helpful to us early C1 owners. I collect a lot of technical articles on the cars I own and have never seen anything on this. You mentioned that the reinforcement plate is subject to rust. Mine is quite rusty. I suspect that perhaps the previous owner simply ran ground wires until the components worked.
Thanks for the clear explanation.

Art

[Dan D.]

Re: 1957 wiper motor and radio grounds

Art, my reinforcement was so rusty I took it out and fixed it. I already had most of the dash stuff out, so it was just a case of drilling out 5 rivets. I sand blasted it and then coated it with Rust-oleum cold galvanizing compound. This stuff is a rattle can and contains 93% Zinc, which makes it very electrically conductive. My car is a driver so I was not so concerned with originality as I was with rust prevention and conductivity. But if one wanted to they could coat it with any of the clear coat products that have been discussed on this forum recently. Just mask off the areas that will have ground connections. It is difficult to buck the end 2 rivets, but it can be done.

-Dan-

[Richard M.]

Gents,

I know this thread goes back 12 years, but I'm researching 1957 wiring and grounds, and I came across this thread which is in line with my work.

I'm helping someone who is creating a colorized (& corrected)1957 wiring diagram. He and I have been on it for over a week, off & on. He making it public, so I plan to upload this to the TDB when it's done, along with some research notes.

It appears the valve cover ground wire is NOT shown in the 1957 AIM anywhere. I spent quite a bit of time and never found a picture of it, in either Sec 8 or 12. Did either of you ever see a physical picture in the AIM? I cannot find one.

Is this valve cover source ground wire Black/White? Do we know what gauge wire? I'm thinking #12 as on later years.

I see in one of the old wiring diagrams it is shown as B/W, and in the harness it becomes all Black to other ground wires.
1956WiringDiagramGrounds.jpg

It then(via a junction in the harness), attaches to the driver side dash reinforcement below the headlight switch area as shown below in the AIM. The AIM shows Black, which leads me to believe the Black/White from the valve cover is spliced in the harness then becomes Black to the dash.

A question....
What is this wire color on the dash reinforcement on your 57's? Is it Black, or Black/White?

AIM Sec 12 - Showing Black ground to the reinforcement with a bolt at the hood release bracket.
This is the ground from the engine for the entire car. This Black wire in the main harness is internally spliced in the main harness and becomes a Black/White heavier gauge wire, then to the driver side inner rear valve cover attaching bolt.
Also, note the Black ground wire to the bottom of the Headlight Switch. I believe this is there only for Courtesy light activation when the HL Dash knob is turned fully CCW.
DashGrounds.jpg

The Wiper Motor ground is shown as a separate wire, attached to the cowl brace stud at the firewall.
WiperMotor.jpg


DashBraceGrounds.jpg

If you get a chance to check your underdash Ground wiring it would help me confirm the above.

Rich

[Gary C.]

Rich,

My two cents on your ground questions:

1. 1957 did not have a ground wire from the valve covers and AFAIK neither did any 1956’s
2. Dash bottom brace ground wire was black
3. From the 1956-7 JRM 27. Courtesy Lights
   Will operate with ignition on or off. A plunger style remote switch in each door hinge pillar
   activates the lights when either door is opened. Also check for operation by turning light switch all the way counterclockwise.
4. Wiper ground wire is black
5. Motor Mount ground straps were only present on radio equipped 1957
6. Ground wire on accelerator rod to rear intake manifold bolt on top of spark plug wire bracket on non FI cars

Gary
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