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paulywood
02-21-2016, 05:38 PM
I'm running all new wires for my car. I found a couple of parts that aren't addressed in the diagram from American Autowire and I can't find the answers in my assembly manual. There is a part that I think may be the horn relay mounted on the firewall. Going from the drivers side it is past the wiper motor. Can someone confirm if it is indeed the horn relay? There were no wires hooked up to it and no horns in my car. (Anyone have a spare set of horns?:)

The 2nd is labeled a voltage regulator and it is mounted up by the front driver's side headlight. The assembly manual says voltage regulator, there are many wires that go to it, but the upgrade kit from AA doesn't address this in either the engine bay or front light kits. I was wondering if it was obsolete due to the upgrade and change to electronic ignition from points.

If someone can help I appreciate it!

shadowgray396
02-21-2016, 10:04 PM
The voltage regulator is for the alternator. The horn relay is next to the voltage regulator. Unless you have a newer alternator you need a voltage regulator, the new ones it is built in.

mestorod70
02-22-2016, 08:05 AM
relay on the firewall is for the A/C system

BillsCamino
02-22-2016, 08:07 AM
Horn relay is near the brake booster/wiper motor on a '72.
Also, a replacement is near impossible to find. I believe a '72 & '73 item only.

Looks like this...
http://i.ebayimg.com/images/g/aKsAAOSw-jhUHaXf/s-l500.jpg

paulywood
02-23-2016, 10:43 AM
Hmmm, I will get a picture of what I think is the horn relay. The car didn't have AC so it shouldn't be that. Right now the alternator is an old one. I can't find the wiring diagram book I have, must have been misplaced when we moved. Does anyone have a diagram of what goes to the voltage regulator? Anyway to check it to see if it's still working? Wiring was a mess on the car.

shadowgray396
02-23-2016, 02:43 PM
70 may be different, but this is where my horn relay is and what it looks like.

http://i777.photobucket.com/albums/yy58/shadowgray/Final%20Build%2070%20chevelle/Wiring-1.jpg (http://s777.photobucket.com/user/shadowgray/media/Final%20Build%2070%20chevelle/Wiring-1.jpg.html)

chevymaher
02-23-2016, 10:09 PM
Mine is like shadow's on my 68.
I did google ad they were saying it is on the firewall on yours. If my buddy would come over in his 72 I would look.

BillsCamino
02-24-2016, 07:48 AM
Horn relays got relocated on '72 model...on to the firewall.
Trust me...1st hand experience on this.

shadowgray396
02-25-2016, 09:01 AM
Horn relays got relocated on '72 model...on to the firewall.
Trust me...1st hand experience on this.

Yes you would be. Lol.

BillsCamino
02-25-2016, 07:18 PM
Me going back almost 10 years!!!

http://www.chevelles.com/forums/23-member-classifieds/138802-wtb-horn-relay-72-a.html

http://www.chevelles.com/forums/27-electrical-wiring/153336-wtk-resistor-switch-etc-72-chevelle.html

http://www.chevelles.com/forums/45-chevelle-tech/182919-1972-ss-horn-relay.html

paulywood
02-26-2016, 07:29 PM
I identified the relay. It's not the horn relay, it's the T.C.S relay. Does anyone know what that is/does?

chevymaher
02-26-2016, 11:45 PM
Smog device to retard timing.

paulywood
02-27-2016, 11:07 AM
Thanks for the help guys. I'm going to upgrade to a new alternator so that takes care of the voltage regulator and don't need a horn relay, there's one included in my wiring kit that mounts under the dash. Just not sure about the T.C.S. relay.

shadowgray396
02-28-2016, 09:35 AM
I borrowed this from other posts, so Here are a couple of comments I found

TCS=transmission controlled spark. This was a 1970 Emissions idea. The whole idea was give the engine advanced timing (via vacuum advance to the distributor) when it was only really needed, therefore reducing exhaust emissions. The TCS relay is a small relay box that is riveted to the wiring gutter that runs under the hood close to the top of the cowl, you know the one that carries the wire with fuse to the a/c/heater blower.

The TCS solenoid (sol) mounts on the passenger side of the intake manifold by the distributor. It is metallic colored and has 3 wire connector One goes to the carb base (vacuum) one goes to the distributor vacuum advance nipple, one goes to the top of the carb (clean air, no vacuum). A wire runs from your tranny to the relay.

The theory was

When the car is in any gear but drive, the small switch that is in the side of the tranny is not activated (not grounded), when you put the car in drive ( I guess 3rd or 4th with a stick shift) the tranny fluid puts pressure on the switch activating it and grounding the circuit that goes to the relay, this causes another circuit to trip that sends 12 volts via the blue and black wire with flat plug to the solenoid on the manifold, It triggers it to let full vacuum from the carb to the vacuum advance on the distributor.

The original GM relay is still availibe through Year One, OPG, or many other m/o houses. I haven't seen a solenoid for sale commerically until recently.

I believe you can get reproduction TCS solenoids from Ground Up:

another post

I've played with the idea of installing this item. What benefits are there to re-installing this system. Will it hurt performance?

If you just want a good cruiser then don't do it, there is no advantage. It will only hurt performance a little but it definately does not help. To correctly hook it all up and FIND all the correct parts would be a major effort.
By the way the TCS temp sensor that has two lugs on it: one is for low temp and one is for high. Like Coppertop stated this overides the solenoid when its "COLD"(<85deg) and also when "HOT" (>220deg).

This system was one of GMs typical stop-gap, Rube Goldberg deals to meet pollution laws back then. I had a couple cars with this and usually removed it about the second day I had it. Only advantage I can see is the timing retard makes the engine idle a little "meaner" with a big cam. The best vacuuum set up is to use ported vacuum with the connection above the throttle plates which will give advance when the throttle is opened partially. If you have cooling problems in town the manifold vacuum might be the best with full time advance except at wide open throttle. tom

paulywood
03-05-2016, 04:02 PM
I talked to one of the reps at American Autowire and he also said I didn't need it. Thanks for the help guys. I should be able to button up the engine bay wiring next weekend when I'm feeling better.