Gary Lewis Posted June 14, 2023 Share Posted June 14, 2023 Wait! You have an '84 truck. So why use the 1980 circuit diagram? Has someone put a 1980 instrument cluster in it? Ok, I’m a whole, complete, entire, M-O-R-O-N. Went to theatre with my wife (movie was good) but couldn’t go to bed without testing the cluster connector. Before this morning, I never used the 1980 diagram for that specific part. But I swear, for the rest, it was really helpful to help me understanding Big Brother’s wiring. The Haynes 1984 differs too much. SO, tester on hands, I jumped in the truck… and after I tested ALL of the cluster harness wires, NO ONE was illuminating the cluster. ?@#*%?!? «Ok» I thought, «Gary is right when not understanding how the cluster is illuminated». «But it WAS, before I pulled it out from… wait a minute, is it possible that… no, can’t be true…» YES, it WAS true: Behind the dash, well hidden, was lying the rest of the blue/red wire. Can’t say how stupid I feel. This tester session confirmed that the cluster connector wiring corresponds entirely to the one you posted, Gary. Can we zap this part of the thread? And why not zap me at all… Ok, now let’s focus on the tach issue and forget this connector “moron chapter"! I’ll study your diagram and see what I can do. I have a question about the resistor identification: You don’t mention the first "gold" stripe, just the 3 other ones. Any reason? You are NOT a moron! Or, if you are I am as I've been there, done that. So, moving on, I didn't mention the LAST band, which is gold. And the last band gives the tolerance. In that gold means +/- 5%. (This site provides details.) Given that you are looking for a 1 watt 100 ohm resistor with a 5% tolerance. Last, if the 1980 section of the Haynes manual matches your truck on the instrument connector then the book is wrong. That's because the biggest difference between 1980 and 1981-86 is right there in there in that connector. Your 1984 is not wired like a 1980 as the lights in the "eyebrow" were moved around significantly. Link to comment Share on other sites More sharing options...
BigBrother-84 Posted June 14, 2023 Author Share Posted June 14, 2023 So, moving on, I didn't mention the LAST band, which is gold. And the last band gives the tolerance. In that gold means +/- 5%. (This site provides details.) Thanks, I'm absolutely not an electronic guy, but give me the right data and I can weld almost anything (years ago, I used my daughter's binocular to repair an aging broken laptop motherboard, and made it working one more year). Just watch me for the Tach! Last, if the 1980 section of the Haynes manual matches your truck on the instrument connector then the book is wrong. That's because the biggest difference between 1980 and 1981-86 is right there in there in that connector. The positive side of that Cluster Connector journey is that I learned about the fact that all Bullnose clusters aren't necessarily what they appear. Their "behind the scene" is widely important! Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 14, 2023 Share Posted June 14, 2023 So, moving on, I didn't mention the LAST band, which is gold. And the last band gives the tolerance. In that gold means +/- 5%. (This site provides details.) Thanks, I'm absolutely not an electronic guy, but give me the right data and I can weld almost anything (years ago, I used my daughter's binocular to repair an aging broken laptop motherboard, and made it working one more year). Just watch me for the Tach! Last, if the 1980 section of the Haynes manual matches your truck on the instrument connector then the book is wrong. That's because the biggest difference between 1980 and 1981-86 is right there in there in that connector. The positive side of that Cluster Connector journey is that I learned about the fact that all Bullnose clusters aren't necessarily what they appear. Their "behind the scene" is widely important! Welding with a binocular? Wow! That's impressive! Yes, the 1980 clusters were different in that the warning lights were in different places. But that is fairly easily changed by re-pinning the connector so you can use an 80 cluster in a later truck or vice versa. Link to comment Share on other sites More sharing options...
BigBrother-84 Posted July 20, 2023 Author Share Posted July 20, 2023 https://forum.garysgaragemahal.com/file/n136873/gauge-pin-out_with_circuit_ID.jpg Long story short: 1- I repaired the «Sick Tach», but once installed it didn’t work, completely dead. 2- Went to my local salvage yard and got an identical one for 20$, but this one looking in really good shape. 3- Installed it and…. Dead too. 4- Opened the hood and unwrapped my so well protected harnesses. 5- Discovered the tach wires, well preserved… I simply forgot that they were lying there and that I wrapped them with the rest of harness when I cleaned up the under hood wiring. Ok, now that I located them, I am wondering where the red/yellow one is supposed to be connected. I know where to re-connect the green/yellow dots (11) and the black/light green dots (12) ones. Any advice about where to re-connect the red/yellow hatch (13) wire? Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 21, 2023 Share Posted July 21, 2023 https://forum.garysgaragemahal.com/file/n136873/gauge-pin-out_with_circuit_ID.jpg Long story short: 1- I repaired the «Sick Tach», but once installed it didn’t work, completely dead. 2- Went to my local salvage yard and got an identical one for 20$, but this one looking in really good shape. 3- Installed it and…. Dead too. 4- Opened the hood and unwrapped my so well protected harnesses. 5- Discovered the tach wires, well preserved… I simply forgot that they were lying there and that I wrapped them with the rest of harness when I cleaned up the under hood wiring. Ok, now that I located them, I am wondering where the red/yellow one is supposed to be connected. I know where to re-connect the green/yellow dots (11) and the black/light green dots (12) ones. Any advice about where to re-connect the red/yellow hatch (13) wire? It goes to Fuse 18. But it isn't connected? Link to comment Share on other sites More sharing options...
BigBrother-84 Posted July 21, 2023 Author Share Posted July 21, 2023 It goes to Fuse 18. But it isn't connected? https://forum.garysgaragemahal.com/file/n138604/pg-98-with-gauge-circuit-error_orig.jpg There are two identical red/yellow wires in #13 connector's pin (see precedent picture). I tested the "under hood" one and I confirm it is going to #13. I left it terminated as it was, and the Tach is working. I suppose its #13 twin is connected to the fuse panel. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 21, 2023 Share Posted July 21, 2023 It goes to Fuse 18. But it isn't connected? https://forum.garysgaragemahal.com/file/n138604/pg-98-with-gauge-circuit-error_orig.jpg There are two identical red/yellow wires in #13 connector's pin (see precedent picture). I tested the "under hood" one and I confirm it is going to #13. I left it terminated as it was, and the Tach is working. I suppose its #13 twin is connected to the fuse panel. Yes, there are two wires in that connector, as shown below. And under the hood one of those wires provides power to various carb circuits. Link to comment Share on other sites More sharing options...
BigBrother-84 Posted July 21, 2023 Author Share Posted July 21, 2023 Yes, there are two wires in that connector, as shown below. And under the hood one of those wires provides power to various carb circuits. Ok, thanks Gary. So, in my case, it's ok leaving it blanked, since I don't have any carb positive current needs. Link to comment Share on other sites More sharing options...
Gary Lewis Posted July 21, 2023 Share Posted July 21, 2023 Ok, thanks Gary. So, in my case, it's ok leaving it blanked, since I don't have any carb positive current needs. Yes. And, glad you got the tach working. Link to comment Share on other sites More sharing options...
BigBrother-84 Posted July 21, 2023 Author Share Posted July 21, 2023 Yes. And, glad you got the tach working. Yep! I am happy! I didn't verified, but the repair I made to the first "Sick Tach" was probably done correctly... I suppose this journey ended with spare unit in stock. Link to comment Share on other sites More sharing options...
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