1975 Dodge

Moparmat2000

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I used 12V green peel and stick 5630 dimmable LED for backlighting. 5 meters of it was about $7.00 off evilbay. Theres a bunch of colors to choose from. Theres 3 segment cut lines and solder tabs.
 

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Moparmat2000

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GM 4 pin module plug to mopar electronic pickup adaptor. I used 3-1 shrink tubing with heat activated glue, then when the shrink tubing was hot, I bent it to 90° and held it in place till it cooled.
 

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97C1500TJ

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Easy way to check the water temp and fuel level gages to make sure the gage and wiring is good is to unplug the wires from the sending units, then ground the sending unit feed wire to a good ground, flip the ignition switch on and and if the wiring and gage is good the needles should deflect to the full high side. Remember they are 6V gages so dont leave the key on. Just leave it on long enough to get a deflection on the needle to verify the gage and wiring to the sender is good. If you get a deflection on the needle then the wiring and gage is good. Problem at that point is the sending unit, or how the sender is or is not grounding out to complete the circuit.

That truck may have a plastic gas tank. Dodge pickups came with a polyethylene plastic tank in the 1970s. Great to not have rust issues, but the sending unit requires a return ground wire to the chassis. These trucks are really simple. Dont overthink them.
I’ve got a metal tank behind the seat and an auxiliary 30-ish gallon along the side. My fuel selector is disconnected so I’ll have to find a picture of one to get it working.
 

97C1500TJ

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GM 4 pin module plug to mopar electronic pickup adaptor. I used 3-1 shrink tubing with heat activated glue, then when the shrink tubing was hot, I bent it to 90° and held it in place till it cooled.
So this is the electronic thing underneath the distributor cap? I haven’t really messed with electronics aside from antique radios and residential stuff so some of this is foreign.
 

Moparmat2000

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So this is the electronic thing underneath the distributor cap? I haven’t really messed with electronics aside from antique radios and residential stuff so some of this is foreign.
On the FAT cap HEI yes. That's the module. It senses a square wave signal from an electronic distributor. Mopar and Ford electronic distributors of this era emit the same signal as the HEI does. GM did away with the resistor wire that GM cars and trucks had prior to HEI. Ford and Chrysler kept the ballast resistor.

The point of the resistor wire GM used and the ballast resistor ford and chrysler used was to drop the voltage to 6V to prevent arcing of the points ignitions. Electronic has no points, and typically has a .006" air gap between the pickup magnet and reluctor wheel. No points no need to use a resistor. This is why if you convert to an electronic ignition setup with GM HEI module, you remove the ballast resistor and simply connect the 2 wires together. A GM E coil ignition coil off a late model GMT400 works great but any coil with about .3 ohms resistance on the primary works fine. Pertronix makes a cylindrical oil filled .3 ohm coil with a 45,000V output that appears stock and fits stock mounting brackets on the Dodge engine.

Incidentally, I figured out GM using a ballast wire for points by helping a friend with a 69 Malibu he made into a Chevelle SS396 clone. He had a fat cap HEI and the car ignition would start to break up at 4500 rpm. I asked him where his ballast resistor was. He said his car never had one. I ohmed out the hot feed wire from the ignition switch to the firewall bulkhead, compared it to the hot feed wire on the firewall bulkhead to the HEI distributor and it had very high resistance. I unpinned the wire and installed a regular copper wire. Car pulled clean up to 6,000 rpm without breaking up. Problem solved.
 
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Moparmat2000

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How are these wired?
The strip has which side is positive and which side is negative. Its marked with cut lines every 3 light segments and solder tabs to attach positive and negative wires. They are 12V so direct wire em on the dash lamp circuit. Positive to the dash light feed, negative to body ground. Factory orange wires in the dash are gage backlighting. LEDs are polarity sensitive. Negative has to be the ground or they wont light up. Ditto for LED push in bulbs. Best thing to do with those is install them, and bench test with a 12V power supply before installing back in the truck.
 
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Moparmat2000

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I’ve got a metal tank behind the seat and an auxiliary 30-ish gallon along the side. My fuel selector is disconnected so I’ll have to find a picture of one to get it working.
You can still ground the sender wire turn the key on, and check the gage deflection. There should be a ground from the sender to the body return path. The cabs are rubber mounted and there should be a ground return strap from the cab to the frame, the engine to the cab, and the usual battery to engine. Not sure about the 1 ton trucks but typically theres a grounding strap on fuel sending units on the dodge and plymouth cars. It's a clip that clips to the metal fuel tube, and sending unit tube, and acts as a jumper to create a ground path around the rubber fuel line connecting the sending unit to the fuel feed tube.
 

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