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Ground strap questions

harryz

Well-known member
Joined
Jul 5, 2005
Messages
52
Aloha everyone,

Thanks to all the good reference material here on this site I added the ground wires to my taillight sockets and now my brake lights work again. Unfortunately, they are still rather anemic, so the next logical thing to check is if there is too much voltage drop on the ground side of the circuit (i.e. bad chassis ground).

But I have a few questions before I dive into this....

1) Where should the negative cable from the battery attach to the engine? If it makes any difference, this is a 289 / auto trans vehicle.

2) I'm going to replace the ground strap that goes from the back of the passenger side cylinder head to the firewall just because it looks like it's been there since '68 and probably could use replacing. What do you recommend to use to clean up just a small circular area on the firewall for the strap to contact?

3) Do you spray the contact area of the strap with anything after it's installed to keep it from corroding?

4) Are there any other ground straps on a GT/CS?

Thanks in advance,
 

J_Speegle

Well-known member
Joined
Jun 19, 2006
Messages
488
harryz said:
But I have a few questions before I dive into this....

1) Where should the negative cable from the battery attach to the engine? If it makes any difference, this is a 289 / auto trans vehicle.

2) I'm going to replace the ground strap that goes from the back of the passenger side cylinder head to the firewall just because it looks like it's been there since '68 and probably could use replacing. What do you recommend to use to clean up just a small circular area on the firewall for the strap to contact?

3) Do you spray the contact area of the strap with anything after it's installed to keep it from corroding?

4) Are there any other ground straps on a GT/CS?

Thanks in advance,

1) Below the alternator to the block there. Originally a ground wire from the alternator and the battery ground were held in place there. Should find a threaded hole, a stud or a bolt in place

2) The contact would be between the ground strap and the screw head (drew is ground to the firewall through the threads as original

3) Originally know (all the sealant was sprayed before the engine (with ground strap attached) was installed

4) Ither than all the typical ones in the wiring loom I can;t think of any
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
Aloha Harry. The previous post is correct. Thanks again for the hospitality.
Steve
 
P

PNewitt

Guest
Since there are so many owners with taillight brightness problems (lack of), I'm devoting a few pages in the book for the complete servicing of the wiring from the under dash wiring loom, back to the taillights.

I'll include how to check for continuity, and for proper voltage with a multimeter (voltmeter). This will be explained in an easy-to-follow way.

There is a danger of accident, with improper lighting in the taillights, if not getting a "fix-it" ticket.

Paul N.
 
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OP
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harryz

Well-known member
Joined
Jul 5, 2005
Messages
52
Jeff: Mahalo (Thank you) for the info. It's been quite a while since we've talked, hope things are going well for you.

Steve: Mahalo to you, too, and it's always a pleasure to show a new friend around O'ahu

Paul: Good idea to include this topic in the new book. I am assuming that I will find a bad ground connection (or bad grounding strap) while working on this. Would you be interested in my voltage drop readings as a 'real life' example?

Harry Z.
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
PNewitt said:
Since there are so many owners with taillight brightness problems (lack of), I'm devoting a few pages in the book for the complete servicing of the wiring from the under dash wiring loom, back to the taillights.

I'll include how to check for continuity, and for proper voltage with a multimeter (voltmeter). This will be explained in an easy-to-follow way.

There is a danger of accident, with improper lighting in the taillights, if not getting a "fix-it" ticket.

Paul N.

Paul, be sure and explain "load" and "no load" voltages when you do your explaination. If I can be of any help, let me know. For the record, I bead blasted my housings and painted them with a "chrome" paint. Any sockets that were loose got a thin layer of solder applied to the outside to bring back the "press fit" they need for a good contact. Mine seem plenty bright as a result.
Steve

PS. Off topic again but if anyone wants, I have a spare light housing that's damaged. I could go through a restoration of it with pictures.
Steve
 
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PFSlim

Well-known member
Joined
Feb 9, 2004
Messages
1,546
Location
Weatherby Lake, MO
Since we are on the topic of brake lights. Does anyone have this problem and a solution:

My brake lights only come on when I stand on the brakes. Several times, I have had people come up and tell me that my brake lights are not working, however after I depress hard, they work fine. I have troubleshot and believe it must be might brake light switch is not activating at the slightest pressure. I could not see that there is an adjustment. My car is an automatic, if that makes a difference.

Paul
 

mmarsalone

Well-known member
Joined
Sep 10, 2004
Messages
324
Location
New Orleans, LA
Paul,

When I bought my 67' it did the same exact thing. It did turn out to be the switch. I used a jumper wire in the swith connector to make sure the rest of the circuit was good just to be sure. When you put your new switch in, remember to put the bushing back in properly. I'd have to look at mine to make sure how it all goes together. I could take a pic if needed.
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
Same here. The brake lights would work fine in the shop and then I'd go driving and they wouldn't come on. Traced it down to the switch. It was old and didn't move freely, so with the engine running the power assist would apply brakes before the switch moved far enough to activate. New switch-no problem.

Steve
 
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harryz

Well-known member
Joined
Jul 5, 2005
Messages
52
Certainly sounds like a brake light switch problem. Make sure you get the correct one for your brake system - there are different switches for drum vs. power disk brakes. Sounds like you might have power brakes but the drum brake switch.

Just my $.02...

Harry Z.
 

Perkchiro

Well-known member
Joined
May 1, 2004
Messages
1,112
Location
Nixa, MO
Hey Paul, I have a different problem with my brakes. My brake pedal will sometimes not retract fully and the brake lights stay on. There is a slight "play" in the pedal at its fully retracted point. I've thought of installing a spring to pull the pedal back but I'm looking for other answers. Any thoughts?

Steve in Missouri
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
I'm not Paul, but I'll chime in. On power brakes there is an adjustable rod between the master cyl. and the brake booster. If that isn't adjusted correctly, you might have that problem. Wear in the pedal support bushings or the bushings for the rod that goes through the firewall may also contribute some play.
Steve
 

nfrntau

Well-known member
Joined
Aug 15, 2004
Messages
1,020
Location
Rosharon, Texas
harryz said:
Make sure you get the correct one for your brake system - there are different switches for drum vs. power disk brakes.
Harry Z.

Great info. I'm working on brakes right now and would have had this same problem. I'm off to the parts store for the correct switch.

Thanks, Good thread
Bill
 

PFSlim

Well-known member
Joined
Feb 9, 2004
Messages
1,546
Location
Weatherby Lake, MO
Perk

I would think as well that you might check your vac line for your power brake booster. I was thinking that if there is not enough vac, the pedal would stay down. Checking the rod that Steve spoke about is another good idea. Lastly, check to make sure your pedal is not binding or to tight in the pedal assy under dash.

We had a heck of a time with our brake boosters. We changed out 3 or 4 before we found one that would hold vac and make the brakes work. If all else fails, buy a guage set and check how much vac you are getting from your manifold.

Paul
 
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