knever3 Posted April 30, 2014 Author Share Posted April 30, 2014 Wonky huh? C10 is not wht/pnk in my truck, it's blue/yellow. When I test it I get nothing either when the brake is depressed or not. Edit: It looks like that wire color is common with another year, I see that in the '89 manual that's the color it's supposed to be. I also learned that it doesn't come from your brake switch that runs the tail lights, but the switch that's on the cruise control vacuum module. I will look into that one I guess. The Saga continues... Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 30, 2014 Share Posted April 30, 2014 I suspect our TCUs are different. I'm not sure what you have, but the solenoids should ohm out at 12-16 ohms from the firewall connector anyhow. http://comancheclub.com/topic/41001-tcu-era-differences/?hl=tcu&do=findComment&comment=414221 Link to comment Share on other sites More sharing options...
knever3 Posted April 30, 2014 Author Share Posted April 30, 2014 Don, I tested the wires at the firewall and I did get the 12-16 ohms, when I tested the same wires inside the cab at the TCU I got 26-32 ohms for the same three. So I have a few pictures tell me what brake switch plug I am supposed to be using. The one I am using makes the brake lights work. It's pink and blue/black. This is the one I have the two wires from the aftermarket brake switch in. The second exact same brown plug is not plugged into anything. It's pink and blue/white. The third thing is my cruise control that's never worked. It has its own plunger and electrical plug and when I test it I get no voltage on either wire regardless if the brake is depressed. The wires are blue/black and black which tests as ground. So to recap I have two identical brown plugs shown in this picture. I don't know what wire is supposed to be going to C10 on the TCU, but I think it's not getting the brake switch signal so the torque converter is not locking up at all. Thoughts? Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 1, 2014 Share Posted May 1, 2014 I have no schematic for all that - maybe the Renix people can decipher it. The HO setup is pretty simple. The single brake switch has three sets of contacts; one set of NO (normally open) and two sets of NC (normally closed). The NO set is for the brake lights of course, pressing the brake pedal applies 12V across the contacts and illuminates the brake lights. One NC set is for the TCU; when you depress the brake pedal it removes a ground signal from pin C10 on the TCU. The other NC set is for cruise control; pressing the brake pedal removes the 12V signal from the speed control servo. One option you have is to throw in an HO brake switch (easy if you swap in an HO pedal assembly) use a set of the NC contacts for the TCU. I have no idea what you have in the pics - sorry. Link to comment Share on other sites More sharing options...
87MJTIM Posted May 1, 2014 Share Posted May 1, 2014 Let me step in. I have the 87 Electrical FSM. The connector with the Pink and Lt Blue w/ tr is the C249 connector. It plugs into the brake switch. Pink is hot. Lt Blu w/ tr feeds the brake lights. The other connector is the C250. It to plugs into the brake switch and powers the cruise control. The dark blue w/tr is hot to the in-line cruise control fuse then to the cruise control on the turn signal/wiper lever. The pink wire feeds to the C251 connector that feeds into the cruise control module. A brake switch with cruise control will have two sets of pins for the C249 and C250 to plug into. Since you have an auto, does the pink from the C250 match up to the third plug you have? That may be a C252 connector. That jumps from the brake switch to the cruise control module. Link to comment Share on other sites More sharing options...
knever3 Posted May 1, 2014 Author Share Posted May 1, 2014 Thanks for the digging guys. So I have a couple of questions as to what to do next. I have a seperate cruise control module that is installed with its own brake switch and vacuum hose above the normal brake switch with a blue/bk and black wire. Maybe I need a different cruise control? As I read your post it looks like I need the double ended brake switch like this picture so both brown plugs can be plugged into the same switch. I would expect that just running a jumper would work the same way. Image Not Found So what wire is supposed to be "seen" at the C10 on the TCU that's supposed to be the brake switch? I can't find a diagram that links the brake switch to the cruise and to the TCU. I need to go to a few salvage yards and see what's supposed to be in this truck. Link to comment Share on other sites More sharing options...
87MJTIM Posted May 1, 2014 Share Posted May 1, 2014 Attached is the FSM for the cruise/brake wiring. From the wiring diagram, I don't see the cruise running to the TCU. From your picture above, it looks like you have the dual cruise brake switch. You can jump the two brown plugs together, since the switch controls both sets of wires. Link to comment Share on other sites More sharing options...
knever3 Posted May 1, 2014 Author Share Posted May 1, 2014 Yeah I don't have the dual switch, I copied someone else's picture but I will just jump them. Thanks for the info and I will test this out this weekend if time allows. Link to comment Share on other sites More sharing options...
knever3 Posted May 2, 2014 Author Share Posted May 2, 2014 Ok, last night I jumped the second brown connector to the brake switch. I went for a test drive and the torque converter didn't lock up. The search continues this weekend. :( Link to comment Share on other sites More sharing options...
knever3 Posted May 4, 2014 Author Share Posted May 4, 2014 Ok, digging into it where does the blue/yellow wire go from the TCU? It seems I'm missing a wire that the TCU is supposed to see the brake switch. I really need to have all the FSM's for this thing!! Link to comment Share on other sites More sharing options...
87MJTIM Posted May 5, 2014 Share Posted May 5, 2014 The TCU and C10 do not run through the brake/cruise switch. It runs through a separate switch on the brake pedal - C260. Look for a connect in a cross or x shape on the brake pedal. The is the override for the trans convert. Here's a link for the 88 Electric FSM. I found that most of the wiring is the same as 87, but radio is diff as well as some other item. http://comancheclub.com/topic/12083-electrical-manual/ DOWNLOAD IT! SAVE IT! Link to comment Share on other sites More sharing options...
cruiser54 Posted May 5, 2014 Share Posted May 5, 2014 What you're looking for is a TCC switch mounted up near the pivot of the pedal. It's white plastic and has nothing to do with the standard brake light switch. Lt Blu wire and Blu/Trace.......Blk on the other terminal.. I wish I was savvy enough to post photos. Can you? If so, PM me with your email address and I'll send you the photo. Link to comment Share on other sites More sharing options...
knever3 Posted May 6, 2014 Author Share Posted May 6, 2014 Huge update, I called in a little favor from my friend Jerami today and we determined what the problem was together. It was a long hunt but I think we got it. For starters we tested a lot of wires going to and from the brake switch, cruise control, and comfort/power switch. When we were probing all the wires it was obvious that the signal from the brake switch/cruise and comfort/power switch wasn't making it to the TCM. We discovered these two plugs that don't go together. I think one was C115 and who knows what the other one is, we never found it! The flat 3 pin female connector has wires tan, light blue/black, and black/yellow. It just so happens that the power/comfort switch has a black/yellow wire too and a tan. Jerami made a jumper for the two plugs while I watched my son for a while. This is the flat 3 pin female connector. Now onto the second plug. It has 6 wires in it, male with three wires that we could trace. Tan, light blue/black, and black/yellow. Sounds familiar, right? Well we spent some time with continuity and the wires go from the aforementioned switches to the TCU. This is the 6 pin plug, the three wires we tracked down, the other three who knows? So onto the third piece of the pie. There are two brown brake switch plugs and a jumper for the clutch if you have an automatic. We measured the jumper and it contributed 33 ohms of resistance so we cut it out and spliced it together getting rid of that unneeded resistance. Nest was the second brown brake switch. It ended up doing nothing at all. We left it unplugged. The next was that clear plastic plug that goes to the cruise control vacuum brake switch. I didn't trust it so I unplugged it and Jerami made a jumper for it. After the upteenth test drive the torque converter finally engaged. Now, we did probe the C14 on the TCU and supplied 12V earlier to lock it up to make sure the solenoids were working in the trans. It locked up as expected. The fight was why were the wires missing in the first place. This is the jumper to the cruise control brake switch Jerami made up. It looks like I need two things, well actually three. First a new cruise control brake switch. Second, a jumper for those two plugs (and find out if the other three wires are necessary for anything else.) And three a new cruise control module. We unplugged the board and there was some corrosion on the terminals on the board and maybe a short sometime long ago. Does anyone have any of these items that want to sell me so I can get this thing on the road? Thanks again for all your help along the way, you have been instrumental in determining the root cause(s) of this conundrum. Link to comment Share on other sites More sharing options...
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