Proper Grounds and Powder Coat?

[71CHEVYSHORTBED402]

I had much of this project powder coated, including the motor mount perches and frame. When the frame was done I goofed because I forgot to account for grounds. No problem, small sanding discs should make for a clean job. Some questions, and they may lean ignorant and over thinking:

1. I take it PC cancels out a decent ground to begin with? Or is it more the ground is less than adequate?


2. Just as well to remove the PC on the ground strap side only or strip both sides? Strikes me the strap side is adequate. I warned you about ignorant and over thinking it


3. I'm not 100% clear how the cab, fenders and core support are correctly grounded due to powder coat.........

..............3A. The cab, fenders and core support are grounded using a strap from the RH frame rail to the inner fender. So no problem, remove the PC from each hole. But how is the ground completed if the rest of the inner fender is PCd? In other terms, the holes used to mount the inner fender to the core support and outer fenders are PCd.

..............3B. The firewall takes two straps that run to the valve covers. I had originally thought the straps were to ground the cab to the engine, but now that I'm thinking about it, strikes me its more to ground the engine?

..............3C. Is it correct to say the motor mounts, the cab mounts and the core support mounts are not intended to complete a ground? I don't know for sure, but I think the cushions prevent it.

..............3D. Any other ground considerations not mentioned where it comes to PC? I recognize the fixed nuts on the core support should not be PCd. I may have the core support, gussets and inner fenders painted anyway.

4. Know where the ground strap was located on a SWB steel bed? I suspect it uses the hole 13" from the rear of the RH frame rail, and fastens to the bed rail someplace. The bed isn't here, and there wasn't a strap when I pulled it.


OTHER GROUND STRAP (Remove PC): RH front cab mount to cab rail. Seems this does exactly what the strap from the frame to the inner fender does, which grounds the cab, outer fenders and core support.


All input appreciated, thanks

[dmjlambert]

Yes, don't over think it. Just clean the spots down to bare metal where you attach the ground straps. If you want to verify, you can just use a multimeter to check that it conducts. Redundant grounds provide better conductivity and provide for things to keep working if one of the grounds becomes disconnected or corroded or physically fails.

The positive cable and all the wires that branch out from it through the fuse panel provides the electricity going to the electrically-run items on your truck, and the return path goes through the metal of the truck. Both need to conduct pretty close to equally well.

In theory you wouldn't really need any grounds, you could run wires everywhere needed, which conduct electricity back to the negative battery cable. You would really have to evaluate each item carefully to do that, because most items don't have a connector for a negative terminal. For example, the starter just has the positive terminal and the negative or return current flows through its case. Same thing for the parking light/turn signal, windshield wiper switch, horn button, horns, distributor, gas gauge sender, the list goes on and on. The list of items that have both positive and negative terminals is much shorter, headlights, and side marker lights are a couple of those.

[71CHEVYSHORTBED402]

Originally Posted by dmjlambert

Yes, don't over think it. Just clean the spots down to bare metal where you attach the ground straps. If you want to verify, you can just use a multimeter to check that it conducts. Redundant grounds provide better conductivity and provide for things to keep working if one of the grounds becomes disconnected or corroded or physically fails.

The positive cable and all the wires that branch out from it through the fuse panel provides the electricity going to the electrically-run items on your truck, and the return path goes through the metal of the truck. Both need to conduct pretty close to equally well.

In theory you wouldn't really need any grounds, you could run wires everywhere needed, which conduct electricity back to the negative battery cable. You would really have to evaluate each item carefully to do that, because most items don't have a connector for a negative terminal. For example, the starter just has the positive terminal and the negative or return current flows through its case. Same thing for the parking light/turn signal, windshield wiper switch, horn button, horns, distributor, gas gauge sender, the list goes on and on. The list of items that have both positive and negative terminals is much shorter, headlights, and side marker lights are a couple of those.

Yep, I overthink stuff. Appreciate the info.......... I need to learn how to use a multi-meter. I did manage to buy one

Just found this thread, good info. http://67-72chevytrucks.com/vboard/s...d.php?t=405497

[Andy4639]

Grounding these trucks, there are never enough grounds ever!

Battery grounds to motor. Motor ground it to the frame. Ground the cab to the motor and the frame both. Ground the bed to the frame & to the cab.

I have ground wires on both sides of the motor cab and bed to each frame rail on my 71.

[LH Lead-Foot]

I agree with Andy4639, grounds are your friend, but placing on bare metal is best practices, it may allow a little rust over time. I suggest getting a decent digital multi meter and watching some YouTube videos on voltage drop, then practice.
Using "Star Washers" will help cutting into the connector and the grounded metal with a dab of dielectric grease. You can get the dielectric grease in the automotive section of a home improvement store and save some money using permatex brand. Star washers are sold as well with internal or external teeth. A little touch up paint can be applied after all is done.

As mentioned, a DMM, can be used to check resistance on each of your grounds, but as a dealer tech for decades, using the DMM on the voltage scale, with one meter lead on the negative of the battery, then the ground of your choice to check (Before touch-up paint), Start the vehicle, turn on lights, blower fan, A/C, radio and 4-way flashers. With current passing thru the circuits, then return path to ground is alway overlooked. This is when you get a very low accurate reading of the loss of voltage across each connection to actually see what is lost. The average reading should be less than 0.040 volts DC. This only works while current is flowing thru the circuit. It is accurate, quick and never lyes to you. High amperage circuits can be 0.50 volts, like the alternator, a snow plow while working, etc.

With a DMM used for voltage drop, some worry about black or red meter leads go where? Don't worry, you get the same reading and if backward, you just get a (-) negative symbol in front of the reading. Just hook up, read, take note if needed, then go. Used this every time a ticket had an electrical issue as a complaint.

Rules: #1, A test light will only show the absence or presence of voltage.
#2, A DMM can show resistance, voltage or loss of voltage across a component.
(Note: In a series circuit, all of the voltage is consumed by the device, but each switch, connector, fuse with have some loss of voltage, but add up to battery voltage)
#3, A Lab Scope will show the actual activity in a circuit, either voltage or current with a inductive amp clamp is used. Same for DMM if higher that the meters capability, like full fielding the alternator and taking a measurement.

A Lab Scope with an amp clamp, on a DC motor, will show the current flowing thru the brushes, into the commutator plates, into the windings, back to ground. So it produces a wavy up & down pattern that is consistent. A bad DC motor is east to spot at this point, due to wear on the brushes or plates.

Just get a decent DMM, learn to use it and be comfortable with the readings you get and what it means. Sorry to be long, but I taught 6 electrical classes for ACDelco in 6 midwest states / 13 tech schools.