juggalo1788

I'm a newb to corvettes I just got a 86. With the manual trans and my question is about the overdrive part I notice that it will engage on its. Own when it is warmed up like 145 degrees but after that it wont engage again like once it gets upwards of 190 degrees and the button does not work either so what is causeing the overdrive to work at a colder tempature then stop at a hotter tempature also the switch does not work at all press it nothing happens no light any help would be really great

AGENT 86

The ECM will engage overdrive once it's happy with the info it's getting from sensors, coolant temp etc. It will also disengage overdrive under the right conditions.

If your OD is coming on and the switch is doing nothing, I would test the wiring to OD relay and check the adjustment of OD switch.
There is a long T bolt that runs between switch at base of shifter, and button on top of shifter. Turning that T bolt will raise and lower the one side of OD button. If raised too much, the switch may forced closed, and if too low, the switch may not be triggered.

Some info from my 86 FSM

http://members.shaw.ca/agent86/Overdrive-manual.pdf

juggalo1788

At 190 degrees or so overdrive will not kick back in no light or anything press the button and there still nothing it only works if like I fire it up after it sat all night drive about 2 miles then it will kick on and everything and the other day it came on but when I floored it the over drive would not kick me out into my gear stayed in OD even when 100% throttle

AGENT 86

You may want to have a close look at the wiring going to OD relay. There is a chance there may be an intermittent short due to shrunken wire insulation. While you are there, you can do some voltage tests.

vetteoz

They never give a problem