1982 GLT more than 150,000 miles

The overdrive has recently taken to occasionally waiting for 15-30 seconds before engaging (after the button is pushed). I rehabed this car about 35,000 miles ago. At that time the fourth gear sensor was replaced, the OD relay was replaced with a new one (soldering didn't work), the bottom plate was removed and cleaned up and it was filled with synthetic auto trans fluid.

The fluid level is up where it belongs. Sometimes when I push the button the OD light will come on and it will shift immediately. Other times when you push the button nothing happens. No light, no relay click, no shifting. 15 to 30 seconds later without any addtional switching the relay clicks, the OD light comes on and it shifts into overdrive.

Under the car in the garage with the engine off with a meter on the solenoid lead and the ground I can verify that pushing the OD button does not always deliver 12V to the solenoid. Same behavior as on the road. Push the button nothing happens immediately, but after a varying delay period the light comes on the relay clicks and the 12V shows up at the solenoid.

It would seem like a relay problem and I plan to open it up and resolder it but can anyone explain the weird behavior I'm seeing. Evidently the button on the shifter is not simply supplying a momentary 12v like the setup on the AW's. How do these relays work. Any insight other than proceeding with the resoldering?

Randy