1972 Wiriing. What is a "shortening bar"?

[Mike E.]

On page 12-91 (wiring diagram) of the 72 Chassis Service Manual, on the left side of the page in the center, where it shows the TCS delay relay, it shows "shortening bar RPO LS5". First of all, what is a shortening bar, and secondly, am I interpreting it correctly that the shortening bar should be used instead of the delay relay?

[Randall K.]

Re: 1972 Wiriing. What is a "shortening bar"?

This shorting bar is essentially a piece of insulated steel that plugs into the relay socket to supply permanent continuity in the circuit. I have the same thing in my '72 LS5. Sorry, no picture from when I had mine apart last year.

Randy

[Ray G.]

Re: 1972 Wiriing. What is a "shortening bar"?

Hello Mike;
I was taught shorting bars distribute heat in a specific electrical circuit and limit overheating. I've seen it spelled "shortening" and "shorting". I guess either spelling makes the point.
my .02

[Mike E.]

Re: 1972 Wiriing. What is a "shortening bar"?

Thanks, guys. "shorting bar" makes more sense than the GM "shortening bar" did. I should have asked a third question: and where does one find one of those?

[William C.]

Re: 1972 Wiriing. What is a "shortening bar"?

I believe they were a piece of Brass stamped with 1/4 inch plades to match the configuration of the "56 series" female terminals used at that time. The AIM might have the part number as they were likely installed at the assy plant

[Mike E.]

Re: 1972 Wiriing. What is a "shortening bar"?

72 AIM, on LS5 page A10 calls it a "jumper strip" and calls out part number 8905858. Where do I find that? Or do I just stick a wire of the same gauge with spade connectors? Additionally, what does the elimination of the relay on the LS-5 imply regarding the operation of the TCS vs. other engine options?

[William C.]

Re: 1972 Wiriing. What is a "shortening bar"?

72 AIM, on LS5 page A10 calls it a "jumper strip" and calls out part number 8905858. Where do I find that? Or do I just stick a wire of the same gauge with spade connectors? Additionally, what does the elimination of the relay on the LS-5 imply regarding the operation of the TCS vs. other engine options?

The jumper means the relay was not used in the circuit and the wires were jumpered together by a piece of flat metal stock formed into two 1/4 inch wide stock in a "U" shape (.032 inch thick stock) . You can achieve the same effect with two terminals and a wire to effect the jumper function.

[Monte M.]

Re: 1972 Wiriing. What is a "shortening bar"?

EDIT:
I took a better look and know where it is supposed to be. A nice picture would be nice though. I actually think I have one, but did not know what it was.
Thanks Again,


I do not mean to high jack the thread, but does anyone have a picture of what was originally there. I too have one of these LS-5 cars and am not familiar with this piece.
Can someone explain exactly where it was originally. I have pictures of forty or fifty 72, LS-5 engines. Is it in a location where it can be seen in a picture with the air-cleaner off?
Is it something we can actually replicate if we have a decent mechanical ability going for us?
Thanks guys,

[Mike E.]

Re: 1972 Wiriing. What is a "shortening bar"?

Monte,
the information I have found indicates that the relay was to be attached to the under dash brace above and behind the map pocket. The bar would obviously be at the end of the wiring that went to the relay,so right in that area. Not visible without the dash partially apart. Mine had a PO with a small wiring fire, and he gutted and threw everything under the dash and "did it himself." It ran well, but hardly anything electrical worked.

[William C.]

Re: 1972 Wiriing. What is a "shortening bar"?

OK guys here is what it was. If you have one of the delay relays used on all others except the LS5, look at the two terminals. Note the width and thickness (.032 thick brass) as well as the spacing between them. Imagine the same two terminals except not entering the relay, but connected together as they were formed from one solid strip of brass (all .032 thick) using that part allowed the system to work all the time without the delay, LS5 only. Sorry I don't have a print, but the ends that insert into the harness are shaped the same as all the other 1/4 inch wide .032 thick blades used on the car. one thing I don't know is if the connection area between the blades has a dipped insulation coating or not. Hope this helps.

[Mike E.]

Re: 1972 Wiriing. What is a "shortening bar"?

Bill,
thanks for you help. Can you, or anyone suggest why this rather than the relay on LS-5 cars?

[Randall K.]

Re: 1972 Wiriing. What is a "shortening bar"?

Mike - I had a similar series of questions when I had my car apart. I believe the TCS relay is in the wiring harness behind the driver-side instrument cluster. See the thread at this link.

https://www.forums.ncrs.org/showthread.php?92404-72-454-auto-TCS-system-questions

Randy