Pls help identify this on my firewall
 

What are these plug relay type things on my firewall (driver side)? Its a 1971 Suburban. The one that is unplugged clicks when the battery is connected and seemed to be causing my battery to drain. Since unhooking it I haven't found anything that is no longer working. I'm not sure if its even a factory item as there has been lots of 'customizing' to its wiring over the years.

http://67-72chevytrucks.com/gallery/.../IMG_13802.JPG

Your help is appreciated.

Re: Pls help identify this on my firewall
 

Those two back to back relays are part of the Transmission Spark Control setup. Mine was disconnected and the three wire harness along the passenger (RH) side valvecover had the plugs cut off. In order not to spark an emissions control debate, do a search for that. I fished the wires and those relays out and removed mine. Do a search for TSC or transmission spark control in the advanced search tab and there is a lot of info about it, it’s function and removal if you choose to do so.

Re: Pls help identify this on my firewall
 

rechinca has it right. Since you haven't missed it, you can strip the wires out of the harness, and if you still have the thermal switch either on the intake manifold or the thermostat housing, you can toss that too. It was used to reduce Hydrocarbon emissions back in the day. If you aren't using this switch, the vacuum to the distributor will hook directly to the carburetor.

Re: Pls help identify this on my firewall
 

Thanks for the help. I was worried something important was no longer operational. I checked all the controls and lights multiple times.

I'll do some searching so I can understand exactly what it was supposed to do. This was converted from a inline 6 to a 350, so I think it was probably disconnected long ago. Vacuum from the dist is currently routed to the carb.

Re: Pls help identify this on my firewall
 

Now that i know what to search for, I see this question has been answered a number of times. Thanks for taking the time to answer it again!

Re: Pls help identify this on my firewall
 

Hey, I just came here to listen to a story 'bout a man named Jed...

Re: Pls help identify this on my firewall
 

Yes, it's the transmission controlled spark setup. All it did was to keep your vacuum advance from working until the the engine was fully warmed up and you were in high gear.
It's not needed and you can follow the wires to remove all of it. There's also a vacuum solenoid on top of your intake that can be removed as well.