WhalePirot
Well-known member
My overdrive stoped working and I complicated the issue, of course. Y'all know the logic is complicated and a bit twisted, as it comes from the factory, but, I be expert at complicating things.
With the '90 Camaro ECM and a custom chip in this modified '84; the high heat working on the wire insulation; aging relays...do-dah......
Now that I understand the operation better than ever, I thought I'd share. There are two pathways of control. One is the ground and one is the 12vdc. Both meet at the relay.
The ECM controls the ground path, which gives the gear selection logic and kick-down, plus the denial of O/D until closed loop operations are happening. Gear selection comes from the various switches aside the tranny. 2nd and 4th have wires running to the ECM, for its logic. The 1st gear switch is different, in that it is in series with the +12vdc and the console switch, feeding the O/D solenoid inside the Nash. There is also a fluid pressure switch in series; inside the unit. W/O fluid, there is no pressure, nor is there enough until about 25 mph. This protects the unit, but complicates the troubleshooting, as simply applying 12vdc to the exterior 'tang' will not trip the solenoid; that is, until there is fluid pressure.
To simplify where the problem lies:
1) If the console switch does not light the dash O/D light, there is a control problem, outside the unit. That light is fed from the same wire that feeds the first gear switch. It gets power from the GAUGES fuse.
2) If the light illuminates with the switch, but the O/D will not engage, the problem is probably inside the unit. I say probably because the 1st gear switch is downstream from the console switch. Guess where my car's problem was.
It had me scratching numerous body parts and coloring wiring diagram, making notes and simplified diagrams; jacking and unjacking the car. All this was stretched out because I'd forget what I had learned and found when off at work for a few weeks.
I was going to simplify the wiring and bypass the ECM. After finding the two pathways, and being uncertain if I should control the ground or the +12 circuit to the relay, it turned out to be easier to allow normal function and jumper the faulty 1st gear switch until I can buy/replace it. Why are simple fixes so complicated?
Now, if I can get the kickdown to work. It is probably not programmed into this ECM. I know that, y'all know, that the cable that links to the throttle is not for kickdown; rather for harder/softer engagement of the O/D, based upon throttle position.
Thanks to the 'new' Nash experts in NY http://www.skspeed.com/ ; the boys who took over from excellent, Paul, at http://www.5speeds.com/dne.htm
just know that you must call them, as there is no online link for our beloved 'Nasher'.
With the '90 Camaro ECM and a custom chip in this modified '84; the high heat working on the wire insulation; aging relays...do-dah......
Now that I understand the operation better than ever, I thought I'd share. There are two pathways of control. One is the ground and one is the 12vdc. Both meet at the relay.
The ECM controls the ground path, which gives the gear selection logic and kick-down, plus the denial of O/D until closed loop operations are happening. Gear selection comes from the various switches aside the tranny. 2nd and 4th have wires running to the ECM, for its logic. The 1st gear switch is different, in that it is in series with the +12vdc and the console switch, feeding the O/D solenoid inside the Nash. There is also a fluid pressure switch in series; inside the unit. W/O fluid, there is no pressure, nor is there enough until about 25 mph. This protects the unit, but complicates the troubleshooting, as simply applying 12vdc to the exterior 'tang' will not trip the solenoid; that is, until there is fluid pressure.
To simplify where the problem lies:
1) If the console switch does not light the dash O/D light, there is a control problem, outside the unit. That light is fed from the same wire that feeds the first gear switch. It gets power from the GAUGES fuse.
2) If the light illuminates with the switch, but the O/D will not engage, the problem is probably inside the unit. I say probably because the 1st gear switch is downstream from the console switch. Guess where my car's problem was.
It had me scratching numerous body parts and coloring wiring diagram, making notes and simplified diagrams; jacking and unjacking the car. All this was stretched out because I'd forget what I had learned and found when off at work for a few weeks.
I was going to simplify the wiring and bypass the ECM. After finding the two pathways, and being uncertain if I should control the ground or the +12 circuit to the relay, it turned out to be easier to allow normal function and jumper the faulty 1st gear switch until I can buy/replace it. Why are simple fixes so complicated?
Now, if I can get the kickdown to work. It is probably not programmed into this ECM. I know that, y'all know, that the cable that links to the throttle is not for kickdown; rather for harder/softer engagement of the O/D, based upon throttle position.
Thanks to the 'new' Nash experts in NY http://www.skspeed.com/ ; the boys who took over from excellent, Paul, at http://www.5speeds.com/dne.htm
just know that you must call them, as there is no online link for our beloved 'Nasher'.
