I followed the flow chart in my FSM and all things checked out fine with the test light so I spent the day pulling the pan and changing out the solenoid hoping that maybe it was a piece of thrash keeping the converter from locking up.I was wrong.My tests tell me the converter should be locking but it isn't and I do not have the tools to check the fluid pressures while running. Does anyone have any ideas and or suggestions? I have never had the torque converter lock since I have owned it BTW (less than a year). I believe it has been out of the car before because the clip on the VSS connector is broken. I did not think the converter clutches are prone to failure. 89 C4 132000miles...
Thanks

You are right. Lock up friction material is not prone to wearing out. It is prone to delaminating, or glaze and chatter.
GM used about 15 different wiring arrangements for lock up. You need to check the pressure switches in the valve body, check for 12 volts on terminal A, and check the brake switch for correct adjustment.
FSM is your best tool here.

had 11.6v and switch works and the test light on aldl term f shows everything checking out as it should. According to the FSM the light goes(grd solenoid/energizing) out above 40mph and when temp exceeds 135. Comes on (ungrounding solenoid/open)with brake tap. No change in RPMs... so I thought it had to be the solenoid sticking but it appears not. Freaking thing is driving me nuts. And on the test ride after all that I get a 32 code thrown. Looks like the EGR diaphram is gone. I see the sensor on fleabay for 500!

Remove and test the pressure switches in the valve body. They are very prone to failure.

I was going to suggest the brake pedal switch but you already confirmed it to be working. Unless something in the tune was changed to keep it from locking I have no other advice for you.

Quote:
Was just looking in the FSM at the YDM model trans used in '90 Vettes
Shows TCC power path; brake switch - solenoid - to ground at ECM.
But something I had not noticed or seen mentioned before is it has a side path to ground through the temp switch and 4th gear switch
giving lockup in 4th gear without ECM control ( once temp switch closes )

I believe the temp switch is set high as in overheat protection trying to force lock up to cool the tranny. I may be wrong though. Sure would not be the first time. Governor seals went out in the ZF tranny in my Saab so I was doing that today. Might wait a week or two to start back on this one. Drives perfect except for the no lockup. I also see the Transgo Kit has a no wire lock up I assume for retrofits. Just an idea. I would prefer to make mine work as intended so I will follow Pete's suggestions and start checking the four (is mine the only year with four?) pressure switches.

Quote:
Wiring the solenoid to ground through the 4th gear switch ( bypassing temp switch ) is a popular way for retrofits.
Gives lockup any time trans is in 4th and release from brake switch without needing control from a manual switch or vac switch as commonly used in some kits

Not relevant to your circumstances but I have also seen other homemade setups where they also wired in the dash switch giving the option of manual lockup in the gears and auto lockup in 4th