A Little Help With 1970 Tcs

[Lynn H.]

Since I am sitting here, and you guys see how much I enjoy posting, I thought I would throw this out and see if someone can help me with "todays dilemma" at my house.
I recently purchased a real cream puff 1970 Cadillac Sedan de Ville (52K miles), that is ultra original and documented better than any Corvette I have every had. This is not a car I know much about and I only purchased it to help out a friend who was in financial trouble and to turn it.
This car has TSC or Transmission Controlled Spark (like my 70 convertible??) and the solenoid was unplugged when I got it. I did some minor clean up in the engine compartment, and did a tune up (plugs,cap wires, etc.) and I plugged the solenoid back in, assuming someone had unplugged it for possible performance reasons. It seems to have caused me some trouble, as after plugging it in, I get an intermittent generator light (bright in park, goes out in reverse, barely visible in drive).
Since I do not have much to work with, except an older chiltons or motors manual, my Corvette related question here is:
Did this TCS thing work the same across the GM line, and can I trouble shoot this the way I would my 70 Corvette if it had the same problem? I have lots of Corvette reference material for troubleshooting.
If I understand the information I do have (on the Caddy) correctly, what it does is disconnect the vacuum advance when the car is NOT in high (third) gear, for emissions purposes.
I know I can probably just unplug it and make the light go away, but things like this bug me.
I have removed the alternator and regulater and had them tested at a reputable starter and alternator shop where I do business and they both check fine.
Any information or knowledge on this would be very much appreciated, as well as helpful when I get to putting my 70 back together.
Thaks in advance,
Lynn

[Terry M.]

Re: A Little Help With 1970 Tcs

Although I have no Cadillac reference material, I am sure that solenoid functions exactly the same as the solenoid on your 1970 Corvette -- if your Corvette was equipped with an automatic transmission. What you described is how it should function -- third (high) gear in the forward speeds and at any time in reverse.

Now you should check the vacuum lines to be sure they are properly hooked up at both ends. Also check the vacuum actuator on the distributor -- maybe that is not functioning. If you have a little hand vacuum pump -- one brand is Mighty-Vac -- draw a vacuum on the actuator. When idling if you apply vacuum the engine should speed up. With engine off the actuator should hold a vacuum for a reasonable length of time.

If all those pass you might want to check that there is vacuum at the hose that attaches to the actuator when the car is running and shifted into reverse. If you have an electrical meter, check the resistance of the solenoid. Open (infinite resistance) of shorted (zero resistance) are both bad.

I hope this yields you something.

[Lynn H.]

Re: A Little Help With 1970 Tcs

Terry,
I did not get a chance to do more than just glance a the Caddy problem today (or thank you for your input), but I did come up with an original 1970 Cadillac service manual (from the guy I purchased the car from-he forgot to give it to me). I do think you are in the ballpark with the solenoid thing because if it is causing problems with the GEN light, it has to be electrical, and what else is there besides the solenoid and the switch in the trans, and the wiring itself that would interfere in some way (short).
As you noted, my 70 convertible is an automatic car, and I think I may have already come up with "some" type of difference in how this system works on the Caddy versus the Corvette. The Cadillac system incorporates a thermal vacuum switch in the mix of the vacuum lines. I did not get a chance to look this up today in any of my Corvette service information, but I do NOT remember anything like that on my 70 when I disassembled it (seems so LOOONG ago). Caddy has a pretty unique climate control setup. Amusing to look at the technologies when you think about how todays systems operate.
Thanks again I will let you know if I find something definitive,
Lynn

[Terry M.]

Re: A Little Help With 1970 Tcs

I do think you are in the ballpark with the solenoid thing because if it is causing problems with the GEN light, it has to be electrical, and what else is there besides the solenoid and the switch in the trans, and the wiring itself that would interfere in some way (short).

As you noted, my 70 convertible is an automatic car, and I think I may have already come up with "some" type of difference in how this system works on the Caddy versus the Corvette. The Cadillac system incorporates a thermal vacuum switch in the mix of the vacuum lines.

Lynn, on my Corvette there is a reversing relay on the bulkhead behind the driver's side rocker cover. I am not sure that the Cadillac has that, and it may only be on a manual transmission vehicle. It has been a while since I had to look at a schematic of that system. so save yourself some potential grief and look at the Cadillac diagrams now that you have the manual.

Is the thermostatic vacuum switch in the TCS circuit? There is a temperature control component to the Corvette system (switch in passenger side head). Perhaps Cadillac used a different method of controlling the temperature component of the system. Another reason to take a look at that manual.