I just thought of another question that’s been bugging me. There is a thermal switch on the right (passenger side) cylinder head. It looks like a temperature sending unit and it has two spade connectors. What is this switch for. What does it do?

Thanks.

 

What year (filling out your profile would help). 70-71'? If so, Sounds like the temp sender for the TCS or CEC emission system. Should be a switch on the trannie also.

 

It's a 71.

You mentioned three things, temp sender for the TCS or CEC emission system and a switch on the trans. How do I know if it is for the TCS and what is the TCS?

As for emissions, there is no emissions equipment on the vehicle so how do I know if the switch is related to the removed emissions system, in which case I assume I wouldn't need it?

The car has a four speed so I don't think it had the switch you're talking about.

Thanks for your help.

 

On your 71 it would be as Duke said for the TCS (transmission controlled spark)Its a smog thing and it would only allow your vacuum advance on your distributor to advance the timing in 3rd and 4th gears.You dont need it and probably dont want it.You probably dont want to know anymore about it so I'll shutup.

 

I'd like to know more about it.
Mine is disconnected and it will stay that way but I'm trying to figure out how an electrical circuit effects the timing.

As far as I can tell timing is changed by one of 3 methods.
Vacuum advance, centrifugal advance and manual advance.

How does the electrical circuit come in to play?
I know it's probably a simple answer but it's not coming to mind right now...

 

It is a pretty simple system. The vacuum that would be available to the distributor vacuum advance is controlled by a solenoid valve. At idle and in neutral, the TCS solenoid valve blocks the vacuum to the distributor vacuum advance and vents the distributor vacuum advance to atmosphere. In 3rd and 4th gear, a switch mounted on the transmission applies power to the the TCS solenoid and thus provides manifold vacuum to the distributor vacuum advance. So, there is no vacuum advance in 1st or 2nd, but only in 3rd and 4th. This was done for emmisions.
In addition, there is a two terminal thermal switch mounted in the passenger side head. When the car is first started and if the temperature is cold enough, one half of the thermal switch, the low temperature switch, will close and activate the TCS solenoid so as to provide vacuum for spark advance for a cold engine, for improved idle and idle speed. Once the engine begins to warm up, that thermal switch will open and the system will go back to normal operation.
If the engine temperature gets too hot, say while you are idling in traffic, the other half of the thermal switch, the high temperature switch, will close and activate the TCS solenoid to provide vacuum advance so that the engine will cool some. Once the engine temperature falls below the high temperature switch limit, the high temperature switch will open and the system will return to normal operation.
This is how the factory system is set up. Of course, after all these years, your particular car may have been modified to bypass some or all of these functions. I hope this helps.

 

Can't explain it any better than Longbros did...heck I dont think I could have explained "as good" as Longbros did.In fact I'm going to copy that into Word so I can pass that explanation on when the question is ask in the future.

 

DWncchs,

Thanks so much for the compliment. Glad to help.

 

Your welcome and thanks for taking the time to write it.
(ps...I added your name to your description.)

 

Thanks for the explanation Longbros!

 

Thanks for all the info. It's too bad I just ordered the thermal switch a few days ago. I thought it played a part in sending info to the temp gauge. Now that I know what it does, I know it wasn't doing anything because my vacuum advance runs off direct manifold vacuum, which is how it will stay.