1975 GT250 wiring madness
Posted: Mon Aug 10, 2015 9:22 am
Hi,
First time poster (I've been following the boards for a while though). Also wanted to thank oldjapanesebikes for assisting me with the gas cap seal.
At any rate, I've been doing a frame-up restore since mid-February (started a blog about it at http://www.machinesofman.com...although I'm playing catch-up on it).
I knew the wiring was going to be a challenge going back together (after I opened up the headlight bucket the first time). I ended up purchasing a NOS main harness as the old one was pretty ratty.
First thing I noticed this weekend, the old wiring harness has kind of a mini-harness in the headlight bucket that is plugged into the main harness - thus the old main harness doesn't have quite as many connections as the new one. (I'm hoping some of you guys have seen this too) - I'm trying to understand if the new harness can replace this mini-harness that's attached to the old factory one - sorry if I'm being vague, I just have no experience with these harnesses.
So, I made my first attempt to hook up the new (NOS) harness. The area by the battery seemed pretty straightforward to hookup.
I kind of just dove into the headlight bucket area after that. First tried to incorporate the old mini-harness to the new main harness - things kind of matched up, but not totally. So to simplify my tests (I do have a wiring diagram in the 250's Haynes manual) - I removed the mini-harness and attempted to just get something working, like the horn or the dash lights. This is when I just hit a brick wall. Nothing would power on (I did have the ignition switch wired using the 4 port block...as well as the 9 port block to the main harness).
I used my multi-meter to verify the ignition switch was working properly (it was). I also verified the main harness had 12v power at the headlight bucket (it does). And verified the horn button completed a circuit when pressed (it did).
But when hooked up, and the key is on, I get no response from neither the horn nor the dash lights. (I also put the horn on some exposed metal - as I wasn't sure if it needs a ground).
Everything was working when I started the restore.
So, I guess what I'm hoping to understand is this this mini-harness and why the factory harness and the NOS harness are a bit different at the headlight bucket (the part number of the NOS matches the number I see on parts diagrams - so I'm guessing there was a revision).
Second, maybe someone could help me (via baby steps) on just getting something to work - because then I think I could build on that.
Finally, the battery fuse is intact (I even replaced it just in case).
Thanks!
Mark
First time poster (I've been following the boards for a while though). Also wanted to thank oldjapanesebikes for assisting me with the gas cap seal.
At any rate, I've been doing a frame-up restore since mid-February (started a blog about it at http://www.machinesofman.com...although I'm playing catch-up on it).
I knew the wiring was going to be a challenge going back together (after I opened up the headlight bucket the first time). I ended up purchasing a NOS main harness as the old one was pretty ratty.
First thing I noticed this weekend, the old wiring harness has kind of a mini-harness in the headlight bucket that is plugged into the main harness - thus the old main harness doesn't have quite as many connections as the new one. (I'm hoping some of you guys have seen this too) - I'm trying to understand if the new harness can replace this mini-harness that's attached to the old factory one - sorry if I'm being vague, I just have no experience with these harnesses.
So, I made my first attempt to hook up the new (NOS) harness. The area by the battery seemed pretty straightforward to hookup.
I kind of just dove into the headlight bucket area after that. First tried to incorporate the old mini-harness to the new main harness - things kind of matched up, but not totally. So to simplify my tests (I do have a wiring diagram in the 250's Haynes manual) - I removed the mini-harness and attempted to just get something working, like the horn or the dash lights. This is when I just hit a brick wall. Nothing would power on (I did have the ignition switch wired using the 4 port block...as well as the 9 port block to the main harness).
I used my multi-meter to verify the ignition switch was working properly (it was). I also verified the main harness had 12v power at the headlight bucket (it does). And verified the horn button completed a circuit when pressed (it did).
But when hooked up, and the key is on, I get no response from neither the horn nor the dash lights. (I also put the horn on some exposed metal - as I wasn't sure if it needs a ground).
Everything was working when I started the restore.
So, I guess what I'm hoping to understand is this this mini-harness and why the factory harness and the NOS harness are a bit different at the headlight bucket (the part number of the NOS matches the number I see on parts diagrams - so I'm guessing there was a revision).
Second, maybe someone could help me (via baby steps) on just getting something to work - because then I think I could build on that.
Finally, the battery fuse is intact (I even replaced it just in case).
Thanks!
Mark