The 1974 Plymouth FrankenDuster has a problem. I recently replaced the guage cluster, heater control panel and a few other things. When I tried to start the car, I got nothing. No spin from the key. I could start it by crossing the terminals on the relay though. NO power to the yellow relay wire, so I unwrapped the wiring tape to the bulkhead. Now, If I remember correctly, 1974 was the only year of the dreaded "Federal Seat Belt Interlock" starter system where the car would not start unless the belts were fastened. This added a few things to the wiring and a fender apron mounted relay/reset unit. Next to the fuseblock is a wierd blue box with 2 master wire plugs going into it. The yellow wire from the starter relay runs into the blue box. I tried using another blue box but the car still wont spin from inside. I tried another ignition switch with no change. I was finally able to get it to start and run by JUMPING a yellow 8g wire to a yellow 8g with black tracer right next to it. GREAT, now it runs but the alternator guage shows a discharge. I ran a jumper from the alternator to the + battery terminal and a handheld meter shows its charging, but the dash guage still shows a discharge.
I'll still keep rooting around to see what went wrong and why, but if I turn up nothing, I could make the "dash wiring bypass" by making the alternator jumper wire a permanent change. I'd just like to know what the heck happened.
Am I correct about the seat belt system being a one year only thing? If not, is this blue box found in 1975 and later cars?

I don't know anything about how the seatbelt interlock is wired in, but I could look at the diagrams. If it were my car I'd run the ground from the relay to the NSS and the yellow wire from the "I" terminal to the ingnition switch and bypass all else.

The wiring that would go to the neutral safety switch was tossed out. I have the BROWN starter relay wire grounded. I like the idea of running the yellow relay wire directly to the ignition switch, since it has power already. Thanks Jim. I didnt expect a good suggestion so quickly. I WILL report back once I get it figured out.

If the ammeter shows a discharge, is is discharging. Time to trouble shoot the charging circuit. As to the seatbelt interlock, if you trace the wiring from the seatbelt relay (the one with the bypass button) you'll find all it does is add another layer of control to the starter relay. On my '74 I just pulled the plug from the seatbelt relay and jumpered the two wires that go to the starter relay at the plug.

Thanks. I did that too and still get a discharge at the guage. What if the guage itself is a turd? I used a handheld tester that showed 13.4 volts at the battery with the engine off and 14.7 with the engine idling WITH the jumper wire from the positive + alternator stud to the starter relay.
This isn't the easiest situation, I know.

If you've jumped from the alternator to the starter relay you don't have the charge current going through the gauge, so I would expect to see the gauge show discharge.

Thats what I was thinking. If I decide to bypass the factory stuff, I'll disable the guage by tying the leads together. The guage will then read straight up all the time. Good time to add a voltmeter anyway.

I'm not sure about the blue box, I have that system in my 74 Dart Sport, but no blue box. The only thing I see is the box on the fender skirt that you mentioned with a reset button.

I know this is no help, but the blue box has me wondering. You would think it would be the same on mine.

i know i had a similar issue and i replaced all the wiring, it finaly came down to the voltage regulator went out and was showing a drain, cheap part i'd replace that see if that fixes the drain

Are you sitting in the drivers seat when you are trying to start it? Had a similar situation with a '74 Satellite Sebring Plus I had. Took me a while to figure out why it wouldnt start standing alongside the car turning key, but would start jumping the relay. There is a pressure sensor in the seat that will not allow car to start without someone in the drivers seat. Yours may have that, too.

Thanks. When I named the car the FrankenDuster, it was certainly for a good reason. This car has pieces and parts from several other cars!
The seats are from a 86 Camaro, reskinned to appear like the mid 70s Duster buckets. It had some other buckets in it when I got it in 2007.
I have another 1974 Duster out back that has the fender apron reset box but NO blue box under the dash. Some '74 models had the box, some did not. I don't know if the 75 and later cars had the same setup.
My dad sold new cars from '68 to 95. He used to tell me stories about the cars he sold, dealerships he'd worked, stuff like that. He sold Chevys in the mid 70s when the Feds mandated the seat belt interlock. NOBODY that we knew wore seat belts then, so this "system" was a pain in the rump for many people. My dad said the salesmen would get in a car from the lot, reach under the seat and unplug the sensor. The car would start and run, but it would still keep the "fasten seat belts" light on the dash.
A local sacramento Mopar Guru also has many tales of the car business in the 70s. He had a 74 Dart towed into the dealership where he was a lead mechanic. No start, just like my car. Everything checked out and he was stumped. He got in, fastened the belts and it started each time. The lady came to get the car and minutes later, she was back in his face. "You SAID the car was fine. well, I can't get it to start!" Joe went over to the car to see that the woman had her purse on the passenger seat. As odd as it seems, the purse was heavy enough to fool the sensor into thinking that a passenger was sitting there UNbuckled. Joe buckled the pass. seat belt and the car started fine.

Theres a post on the A12 and resto forum about a similar No Start issue: No power to the yellow wire. The OP had power at both sides of the yellow wire at the ignition switch pin connector, but it went dead somewhere before the bulkhead, and was dead from the bulkhead to the relay. This may also be the case with my car. I'll poke test my yellow wire from the bulkhead (Dash side) to the ignition switch. If mine also shows a problem there, it appears that it is a more common problem than I thought.

Okay... I wanted to give an update on the wierd problem I had. Maybe it may be of help to someone.
I went over the wiring a few more times and can't find anything wrong besides the 2 components of that seat belt starter interlock crap.
I tried another fender mounted "reset" button. This allowed the key to spin the starter, but as I released the key, the starter kept going. NOT good. This reset button had 5 wires to it, including the yellow and yellow with black stripe wires that follow into the car to that wierd blue circuit board. No matter how I tried to bypass or shortcut the circuit board, the Alt guage showed a discharge. NOBODY is reproducing that blue box, so I ended up tying the yellow wires together. I ran a 10 guage wire directly from the Alt to the battery. The battery shows 13.4 volts when the engine is off, and 14.6 when the engine is at a fast idle. The Alt guage still showed a discharge, so I pulled the cluster and connected the red and black wires together. It reads straight up now. I'll add in a Voltmeter and an oil pressure guage next. THANKS for all the suggestions.

HEY! 4 YEAR OLD THREAD

I am having this problem now. Following the wires adn I am going to get this damn thing out of the circuit.

I'm assuming you can jump the large "batt" terminal and the next to it brown wire "sol" terminal on the starter relay & it will crank. Not sure if the seat belt relay interrupts the yellow start wire power side or the NSS ground wire ground side but if it opens the power side I'd run the "st" terminal on the ign switch to the yellow wire at the "ign" terminal on the starter relay and if it interrupts the grounds side I would ground the "grn" terminal on the starter relay (which will cause it to be able to be cranked/starter in any gear), safety just sayin.

I have my FSM in front of me. I will follwo along. However, the wiring under the hood is terrible. I want to add MSD and clean up wiring, so this will be fun. I just want it to crank from the key before I start, so I know it was working.

Wow...I logged on and saw my name on this thread that I forgot about. I thought that my account was hacked!

i am just going to rewire like the 72 charger, I plyed with a lot of jumpers last night but no start, so, rewire like a normal car.