strange TI wiring harness

[Keith B.]

I was going through dads stash of parts and came across this TI harnnes he pulled from his 67 L79 car. There is a strange rubber boot around it after the amp plug. Has anyone seen such a thing?

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[Ray K.]

Re: strange TI wiring harness

Keith
The TI amplifier unit that Chevrolet offered for Corvettes 1964 and later under GM #3955511 contained a new amplifier with a short section of wire harness ( 12" approx ) with a rubber boot attached and a new connector along with instructions how to splice this new unit into the existing wire harness along the right fender.

Ray

[Keith B.]

Re: strange TI wiring harness

I added a picture since Ray commented. Can anyone else comment

[Duke W.]

Re: strange TI wiring harness

I ran a TI system off a '67 L-88 on my 340 HP SWC for several years beginning in 1968. The harness connector to the amp was a three pin male type with a big rubber boot like in the photo that plugged into a female receptacle on the amp. The second time it failed in 1975 I removed the whole system from the car and set it up on the bench with a 12V battery and an electric drill to turn the distributor. I found corrosion on one of the terminals on that connector and was able to easily correct it, and the system tested good.

At that point I put the whole system in a box and installed the original distributor that I had "blueprinted" and tested to 7000 RPM. Prior to that it had a habit of breaking up as low as 4500 RPM. The first TI failure circa 1970 was when one of the leads from the main power transistor that is mounted to the amp housing popped off the circuit board, and I was able to stick it back in the via and secure it with a dab of solder.

At some point after 1967 the amp was configured with a short pigtail that was connected to the harness a few inches away from the amp. I figure that change was due to the moisture intrusion issue I experienced.

In 1985 I sold the system to David Burroughs who at that time owned the L-88 from whence it came.

GM mounted the TI amp on the front of the radiator support to provide good cooling, but this exposed it to the elements, particularly water. IMO they should have mounted it somewhere inside the car.

I'm glad my SWC did not have a TI system. The single point system is much more reliable, but the distributors were sloppily assembled and weren't well suited for high rev operation without some TLC. The TI system worked perfectly or not at all and gave no warning of impending failure.

Duke

[Terry M.]

Re: strange TI wiring harness

I ran a TI system off a '67 L-88 on my 340 HP SWC for several years beginning in 1968. The harness connector to the amp was a three pin male type with a big rubber boot like in the photo that plugged into a female receptacle on the amp. The second time it failed in 1975 I removed the whole system from the car and set it up on the bench with a 12V battery and an electric drill to turn the distributor. I found corrosion on one of the terminals on that connector and was able to easily correct it, and the system tested good.

At that point I put the whole system in a box and installed the original distributor that I had "blueprinted" and tested to 7000 RPM. Prior to that it had a habit of breaking up as low as 4500 RPM. The first TI failure circa 1970 was when one of the leads from the main power transistor that is mounted to the amp housing popped off the circuit board, and I was able to stick it back in the via and secure it with a dab of solder.

At some point after 1967 the amp was configured with a short pigtail that was connected to the harness a few inches away from the amp. I figure that change was due to the moisture intrusion issue I experienced.

In 1985 I sold the system to David Burroughs who at that time owned the L-88 from whence it came.

GM mounted the TI amp on the front of the radiator support to provide good cooling, but this exposed it to the elements, particularly water. IMO they should have mounted it somewhere inside the car.

I'm glad my SWC did not have a TI system. The single point system is much more reliable, but the distributors were sloppily assembled and weren't well suited for high rev operation without some TLC. The TI system worked perfectly or not at all and gave no warning of impending failure.

Duke

Duke,
There was a TSB (Technical Service Bulletin) issued in December 19, 1967 (68-T-8) instructing whose who encountered the issue you describe to clean the corrosion and pack the connector with Dow Corning Silicone grease -- to be procured locally.

I don't have my AIMs handy to look up when the amplifier with pigtail is called out. The Judging Guide says 1968 had no pigtail and 1969 did, but an exact change point is not called out.

This is probably more than you wanted to know on the subject.

As a Post Script: I am disappointed in the TSB in that it just says to use Silicone Grease. There are several types of silicone grease, and I suspect one is more suitable in this application than another. It would have been nice of Chevrolet to specify which kind of grease to use.

[Duke W.]

Re: strange TI wiring harness

Thanks for the info, Terry. I was never aware of the TSB. After two failures in five years, I was not a fan of the TI system, and I'm certainly not a fan of all the electronics in modern cars. One of the nice things about vintage cars is that they are simple. Most electrical problems can be isolated with an inexpensive multimeter, and most parts are readily available an inexpensive compared to all the black boxes in modern cars.

Fortunately I was able to correct both TI failures at no cost... just a bit of labor.

Duke