I just learned about this forum and have really been enjoying it. This is my first posting.

I'm going through all the electrical wiring on my '71 coupe and have been ordering new harnessses as needed along with other components. I've learned a lot and have definitely become one with my wiring diagram!

I'm trying and failing to find information on components like the blocking relay, anti-dieseling relay, and TCS circuitry, and exactly how they all function. Is there a site out there that might explain some of these mysterious components better? My wiring diagram only shows standard production wiring and a/c wiring (which my car has).

I can't even find these parts on Corvette Central or Corvette America if I do indeed need to replace them.

Any ideas???

Thanks...

 

I am not CERTAIN of the following but saw you had no replies yet so I thought I give it a shot.

I think the TCS system locks out your vaccum advance until you get into 4th gear (that's what is did on my '71 4 speed Cutlass). If you have a swith near the 3-4 shifter lever on the transmission cover and there is(or was) an electrically operated valve between your carb and distributor I am probably giving you good information.

Is the anti-diseling relay the solenoid that cuts closes the throttle tight when the car is shut off? If so, it works by eliminating virturally all of the air so diseling cannot occur after the ignition is off. Before fuel injection, the best that could be done is to shut off the air to the engine as there was always enough fuel in the carb to support combustion via dieselling.

I can't even guess on the blocking relay!

 

I think you're right about the TCS functionality. There's a switch on the transmission in that location, but my car doesn't have a switch/valve between the carb and distributor (I do have an extra wire without a switch though in that area?!!).

Both the blocking and anti-dieseling relays are part of the a/c system wiring. There are no electrical components that attach to the carburetor (and the wiring diagram doesn't show any either), so I think they must intervene and shut off the a/c compressor when they see the need.

I'll keep studying my diagrams...

Thanks for the help.

 

Unless you are trying to make the car correct for judging, you don't want the TCS setup. When I bought my 71 new, it was the first thing I took off and threw away.

 

Looks like all the above info is correct but one of the systems has a temp sender in the rear part of the R/H head so that engine temp is part of the equation also. I don't have any of my information about our cars near the computer so I cannot say for sure which systems uses the temp sender.

 

I consider myself somewhat an expert on the 71 only TCS system. The relays for the system are on the firewall next to the wiper motor. It consists of two relays, a control relay that actuates the solenoid attached to the drivers side of the carb and applies vacuum advance to the distributor when: in reverse, in high gear (3rd on a TH400 via an internal pressure switch or 4th on a 4 speed via a switch mounted next to the 3-4 shift arm), when engine temp is less than 125 or greater than 215 (via the pass. side cylinder head temp switch), and for the first 15 seconds after engine start-up. This is accomplished by the other relay mounted in back of the first.
The blocking and anti-dieseling relays are another system and are mounted inside on the airbox under the dash on the pass. side. On non-AC vettes the anti-dieseling energized the blower fan for 5 seconds when key is turned off. On AC vettes the blocking and anti-dieseling work together to energize the AC clutch for 5 seconds to create a load and prevent run-on. Both of these systems work on mine with no loss of performance or mileage (18mpg on the highway). All the relays are available on ebay for about $25, so stock up. The AIM has the part numbers and the Chassis manual has a great wiring diagram. I have an electronic copy of the factory Emissions Troubleshooting Manual for 71, you can have a free copy if you want. It helps a lot for a 71 only system.
Sorry so long, hope it helps.

 

Dr. Rebuild has the TCS solenoid.

 

...and I assume the woman in the above photo is about to check the functionality of the TCS solenoid...?

 

Missileman,

I could use a copy of that manual with my 71. Can you send me a copy?

Thanks,

Mike

 

To all that would like a copy, the files are too large for me to email. Email me your address and I will mail you a disk (USA only please). Thanks.