~KnuckleDuster~ Posted June 12, 2019 Share Posted June 12, 2019 (edited) Hey guys, so I just upgraded my fuse box to the MSA modernized unit. When I put the battery cables back on the engine electronics and fuel pump kick on as if going to accessory power. If I remove the 20a STOP fuse I can put the cables on and the key will operate the acc power as usual. Any ideas on what can be going on here? Edit: I originally upgraded the box because the parking lamp fuse block was starting to melt out. Edited June 12, 2019 by ~KnuckleDuster~ Quote Link to comment Share on other sites More sharing options...
Miles Posted June 13, 2019 Share Posted June 13, 2019 What car 240z, 280z etc? Any wiring modifications? Re-install the original fuse box to see if it behaves the same way which will eliminate the new fuse box as the problem. You could pull one fuse at a time to isolate the problem to a specific circuit and then go from there. A call to MSA may help. Kinda depends on which MSA tech you get. Quote Link to comment Share on other sites More sharing options...
cgsheen Posted June 13, 2019 Share Posted June 13, 2019 When you installed the new fuse box, did you have to twist the connector on the left side 180 degrees to get it connected? (Did you make sure the green wires lined up with green on the dash harness, blue with blue...) You can also verify the circuits with your multimeter. The Stop and Horn have the same feed through the Ammeter circuit (White) : The Stop comes out on a Green/Yellow, The Horn on a Green/Red. There are five circuits fed directly from that battery (two WR tied to that bus) : - 20 amp Common - Blue/White - 10 amp R Headlight - Red - 10 amp L Headlight - Red/Yellow - 10 amp Dome / Instrument - Red/Blue - 20 amp Park / Tail - Green/Blue Two circuits on the Accessory bus (Blue/Red) : - 20 amp A/C - Blue - 20 amp Wiper - Blue/Red One circuit on the Ignition bus (Black/White) - Flashers - Green Quote Link to comment Share on other sites More sharing options...
~KnuckleDuster~ Posted June 13, 2019 Author Share Posted June 13, 2019 (edited) It's a 73 240z. It's got it's share of wiring modifications for gauges, rb motor misc. I believe I have it isolated to the stop circuit. I don't recall if I had to rotate the connector but the wire colors do somewhat match up..the msa wiring color isn't exact but I double checked that I didn't have it reversed, the plug will only go on one way as well. The stop circuit has constant 12v power on the left side of the fuse bus as it should, with the key to ON there is 12v power to both sides of the fuse is this normal or am I getting two 12v inputs into the same circuit? I'm going to mess with it some more today, might put the old box back in to see if it goes away. MSA doesn't offer returns on electrical equipment so I really hope the issue isn't with the new box. Edited June 13, 2019 by ~KnuckleDuster~ Quote Link to comment Share on other sites More sharing options...
cgsheen Posted June 13, 2019 Share Posted June 13, 2019 The Stop circuit has power on both sides (with the fuse removed) when the ignition is ON? I can't see how that should be correct. It's path is to one side of the hazard flasher and to the hazard switch. With the hazard switch OFF, it should just pass power to the brake (stop) switch (where power should stop until the switch is made). The only "feedback" source should be the hazard switch or the hazard flasher (which also goes back to the hazard switch). Quote Link to comment Share on other sites More sharing options...
~KnuckleDuster~ Posted June 13, 2019 Author Share Posted June 13, 2019 (edited) Correct power is on both side of STOP bus bar with the fuse removed & ignition in the on position. Makes me think it's a manufacturing issue with the new box. Prior to install I had just drove the car to turn it around in the garage and replaced the fuse box. Never had any real wiring issues before this. The hazards don't work anyway so I'm thinking about just leaving this fuse out completely. I don't like the idea of masking a potential problem but the idea of having to comb through all the wiring under the dash to just have the new fuse box just be the issue is a bit of a turn off. Do you think it's worthy of contacting MSA about it? I guess the only true test would be to put the old fuse box back in and see if there's power to both sides of that fuse.. Edited June 13, 2019 by ~KnuckleDuster~ Quote Link to comment Share on other sites More sharing options...
Miles Posted June 13, 2019 Share Posted June 13, 2019 (edited) 49 minutes ago, ~KnuckleDuster~ said: Correct power is on both side of STOP bus bar with the fuse removed & ignition in the on position. Makes me think it's a manufacturing issue with the new box. Prior to install I had just drove the car to turn it around in the garage and replaced the fuse box. Never had any real wiring issues before this. A clue!. The hazards don't work anyway so I'm thinking about just leaving this fuse out completely. I don't like the idea of masking a potential problem but the idea of having to comb through all the wiring under the dash to just have the new fuse box just be the issue is a bit of a turn off. Don't do things like that. Work it out. If things worked before installing the new fuse box, then it is the box or how you installed it and not the wiring under the dash. Do you think it's worthy of contacting MSA about it? It is just a phone call. I guess the only true test would be to put the old fuse box back in and see if there's power to both sides of that fuse.. Takes 5 minutes. Do it. The objective is to repeat the original behavior you saw after the new fuse box was installed. If the problems goes away then it has to be the fuse box or you made a mistake Work logically. The first question I ask people with a sudden electrical problem is: what was the last thing you did just before the electrical problem occurred? For example, a guy with a 240z kept blowing a fuse for the side marker and dash lights every time he turned the lights on. He just kept replacing the fuse each time this happened. So I asked him: "what was the last thing you did to the car before it started blowing fuses?" He replied "I removed the right rear marker light and replaced it" Turned out he mixed up the ground and power wires so each time he turned on the lights there was a dead short in the lighting circuit. Edited June 13, 2019 by Miles Quote Link to comment Share on other sites More sharing options...
~KnuckleDuster~ Posted June 14, 2019 Author Share Posted June 14, 2019 Ok so I put the old fuse box back in. No issues. Checked voltage on the L & R fuse block with ignition on and power was only coming into the left side like it should. I'll be calling MSA tomorrow. 😕 1 Quote Link to comment Share on other sites More sharing options...
Miles Posted June 14, 2019 Share Posted June 14, 2019 Please let us know what MSA says. Quote Link to comment Share on other sites More sharing options...
~KnuckleDuster~ Posted June 14, 2019 Author Share Posted June 14, 2019 Called MSA. They're having me ship the box back to them so they can have the manufacturer inspect it. Luckily my old fuse box still works because this process is going to take a few weeks to figure out. Quote Link to comment Share on other sites More sharing options...
~KnuckleDuster~ Posted July 4, 2019 Author Share Posted July 4, 2019 The fuse box was in fact faulty. MSA is sending me a new unit. Quote Link to comment Share on other sites More sharing options...
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