Antenna ground strap ??

[ChrisWhewell]

Now that I've fixed the antenna on my 90 Reatta, I looked into the one on the 98 Riviera, photo below.  I noticed there's a ground strap from the frame of the car to the tube the antenna resides in, and also noticed it was not present on the 90.  Given that GM theoretically didn't put anything un-necessary in production vehicles out of cost considerations, I'm wondering the benefit of having the ground strap present, and whether I should add one to the antenna on my 90, any thoughts on that ?   Thanks !!

Edited October 22, 2016 by ChrisWhewell (see edit history)

[KDirk]

Not sure why they added that except that maybe for some reason the antenna mount bracket was a good body ground. It is (or should be) a good ground on the Reatta. Are you sure this ground strap was factory equioment and not added in an attempt to address some problem?

 

This raises the related issue of the trunk lid ground. There are only two wires routed into the trunk lid, one for the light and one for the power trunk release solenoid, as both rely on a frame ground. I have had problems in two of my Reattas with the light not working and ran a dedicated ground wire into the lid through the existing loom. I used the antenna mount as the ground point for my new ground wire and it has worked fine.

 

As an experiment, I tried to pop the trunk release with the trunk lid open without this extra ground attached. It wouldn't pop, but worked fine when the lid was closed. I reached the conclusion then when the trunk lid was down, the latch was grounded via the steel catch loop mounted to the rear trunk wall. When open it had no path to ground, which affected both the release solenoid and the light. What I haven't been able to figure out is why the original body ground for the trunk lid is no longer good. Easier to just add the needed wire and be done with it. 

 

[ChrisWhewell]

My trunk latch solenoid was fried when I got the car, so I got a replacement one and put it on but it didn't work, until I ground some of the paint off the trunk where the solenoid bolts attach it, then it worked fine.

[Ronnie]

That ground strap looks like it is made of small braided wires like is commonly used as a drain for static electricity in electronics. GM has used them in some older cars between the firewall and engine to prevent static in the radio. Perhaps it was installed for that purpose ?.

[KDirk]

Interesting. That leads me to wonder if some corrosion formed between the solenoid and the trunk lid. Clearly, trunk lid has to be grounded by way of the hinges as that is the only unbroken contact point to the body possible. Maybe enough corrosion forms between the hinges and the body to create a resistive found and stop the lamp from working.  I still prefer a dedicated ground into the trunk lid and GM was just cheap or lazy to have omitted it to begin with.

[Barney Eaton]

The Delco antenna used on Reattas (and other GM cars) does not need an external ground for the motor to work.

That ground started showing up about 1994 ..........they may have had problems with incoming signals and found the ground solved or help solve the problem

[ChrisWhewell]

42 minutes ago, Ronnie said:

That ground strap looks like it is made of small braided wires like is commonly used as a drain for static electricity in electronics. GM has used them in some older cars between the firewall and engine to prevent static in the radio. Perhaps it was installed for that purpose ?.

 

You're right, it is the braided stuff, it looks like it could probably carry 30 amps if it had to !!   

[Ronnie]

43 minutes ago, ChrisWhewell said:

You're right, it is the braided stuff, it looks like it could probably carry 30 amps if it had to !! 

 

You would think that would be the case but the reason for the loosely braided wire is that RF signals travel on the surface of the wire instead of through it. The small braided wires bundled together to form a ground strap have a much larger surface area than one large wire. Usually they aren't used in high amperage applications -  although for some reason large braided ground battery cables were used in old cars that had 6 volt system. Go figure...