Atlas75 Posted November 9, 2021 Author Share Posted November 9, 2021 That info on the wire connections is correct. And I don't understand why the '80 EVTM shows only two. But the '80 EVTM is strange, so just add that as one more item to prove its strangeness. I got everything wired up the way I wanted it and reinstalled he cluster. I fired up the truck and the tach worked! Next I drained the black fluid like substance from the rear diff and cleaned up the mating surfaces and reinstalled the cover and refilled the diff with new fluid. I also futzed around with a few other things including installing the trim around the cluster. Time to start the truck and park it next to the trailer…and the tach no longer works. I guess I’ll be pulling it back out and double checking everything. I hope it didn’t get ruined somehow. Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 9, 2021 Share Posted November 9, 2021 I got everything wired up the way I wanted it and reinstalled he cluster. I fired up the truck and the tach worked! Next I drained the black fluid like substance from the rear diff and cleaned up the mating surfaces and reinstalled the cover and refilled the diff with new fluid. I also futzed around with a few other things including installing the trim around the cluster. Time to start the truck and park it next to the trailer…and the tach no longer works. I guess I’ll be pulling it back out and double checking everything. I hope it didn’t get ruined somehow. I doubt it got ruined. Probably just a connection issue. Like maybe your ignition switch didn't come all the way back to Run. That happens a lot in cold weather as the grease in the switch and the linkage gets stiff. There are multiple contacts in the switch and the ignition contacts always seem to make before the accessory contacts do. So it isn't unusual for a lot of things not to work if you don't roll the switch back a bit more. Link to comment Share on other sites More sharing options...
Atlas75 Posted November 9, 2021 Author Share Posted November 9, 2021 I doubt it got ruined. Probably just a connection issue. Like maybe your ignition switch didn't come all the way back to Run. That happens a lot in cold weather as the grease in the switch and the linkage gets stiff. There are multiple contacts in the switch and the ignition contacts always seem to make before the accessory contacts do. So it isn't unusual for a lot of things not to work if you don't roll the switch back a bit more. After reading your post I think I should have done things differently. I took battery literally and connected “B” to an unswitched 12 volts (I tapped off the electric brake controller which has a wire direct to battery). Switched 12 volts would make more sense. I wish I would have paused and thought about it for a minute. I wonder if the tach will draw power when the truck is off? Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 9, 2021 Share Posted November 9, 2021 After reading your post I think I should have done things differently. I took battery literally and connected “B” to an unswitched 12 volts (I tapped off the electric brake controller which has a wire direct to battery). Switched 12 volts would make more sense. I wish I would have paused and thought about it for a minute. I wonder if the tach will draw power when the truck is off? It'll draw some. But if it has power all the time then the ignition switch isn't the problem. Link to comment Share on other sites More sharing options...
Atlas75 Posted November 13, 2021 Author Share Posted November 13, 2021 It'll draw some. But if it has power all the time then the ignition switch isn't the problem. How do the heater controls come out of the dash? They are mounted behind the metal part of the dash. Do they come out the bottom somehow or do you need to disassemble most of the dash to get them out? Link to comment Share on other sites More sharing options...
FuzzFace2 Posted November 13, 2021 Share Posted November 13, 2021 How do the heater controls come out of the dash? They are mounted behind the metal part of the dash. Do they come out the bottom somehow or do you need to disassemble most of the dash to get them out? If you ask the PO of my (parts) truck he broke the dash to get it out. I had to graph part of my old non-AC dash into the AC dash I needed to use. I really dont know as I installed the HVAC in the dash before I put the dash in the truck. Later I needed to pull it for something and gave up. I cant remember if it will come up through the radio opening or not as I think I still had the radio installed and did not want to pull it to find out. Good luck and if you find how it comes out post it up. Dave ---- Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 13, 2021 Share Posted November 13, 2021 How do the heater controls come out of the dash? They are mounted behind the metal part of the dash. Do they come out the bottom somehow or do you need to disassemble most of the dash to get them out? The factory service manual (Documentation/HVAC/HVAC Systems and then the 1981 FSM & the A/C-Heater Systems tabs) shows the procedure below: Link to comment Share on other sites More sharing options...
Atlas75 Posted November 15, 2021 Author Share Posted November 15, 2021 The factory service manual (Documentation/HVAC/HVAC Systems and then the 1981 FSM & the A/C-Heater Systems tabs) shows the procedure below: I got it out. The ash tray needs to be removed and then you can tip the back of the heater controls up and drop the front down and it comes out. It’s tight but it comes out. Thanks for the help! Link to comment Share on other sites More sharing options...
Gary Lewis Posted November 15, 2021 Share Posted November 15, 2021 I got it out. The ash tray needs to be removed and then you can tip the back of the heater controls up and drop the front down and it comes out. It’s tight but it comes out. Thanks for the help! Yep, that was part of Step 4. But you didn't have to take floor register duct out? Anyway, glad you got it out. Link to comment Share on other sites More sharing options...
Atlas75 Posted November 15, 2021 Author Share Posted November 15, 2021 Yep, that was part of Step 4. But you didn't have to take floor register duct out? Anyway, glad you got it out. I did not remove any ducts. That may have made it even easier but I did get it out without removing them. Link to comment Share on other sites More sharing options...
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