Finer Points Of Electrical Grounding - And It's Importance!
 

Grounding finer points:

Often, various electrical/electronic problems with our trucks eventually turn out to be the result of poor or deteriorated grounds at various points.

Often, engine bolts are used if they happen to be close to the point we need to ground some new piece of equipment, or perhaps one of the existing body grounds DC uses for existing grounding.

MANY of the bolts used on our engines are ANODIZED, or use a coating that totally PREVENTS voltage/current flow - here's a pic of one of those bolts from my '02, showing what happens if an ohmmeter is used to test for current flow thru that coating:

http://img148.imageshack.us/img148/8781/grounddo5.jpg

Note there is absolutely NO deflection of the meter pointer - NO current flow!

Here's another pic of that SAME bolt, with the probes moved to an area of the bolt where the coating has been removed with a wire brush:

http://img148.imageshack.us/img148/9981/ground1nn7.jpg

NOW, there is a full-scale deflection, zero resistance - just what we want!

This particular bolt was used to secure the ground return for the grid heaters on my '02 24-valve engine:

http://img214.imageshack.us/img214/2770/ground2yx3.jpg

There's a LOT of current flow at that point, and a GOOD electrical contact is needed for proper operation - after wire brushing the resistance coating from the thread area and underside the bolt head where it contacts the ground lug, prior to re-installation, I applied a liberal coating of anti-oxidant paste at all contact points to KEEP the contact functional:

http://img297.imageshack.us/img297/9003/ground4eq5.jpg

The sheetmetal grounding points deserve attention as well - I normally lift all the factory installed grounds up, take a Dremel tool to grind the paint away, exposing bare metal - then use the same paste to preserve the improved grounding point. Here is one such point, with the added large braid I've added to the existing one for better high-current flow - I did the same on BOTH batteries:

http://img234.imageshack.us/img234/6895/ground3re3.jpg

Consider that MANY devices on our trucks include circuits that have very low resistance - in those circuits the addition of a mere FEW ohms resistance can make a SERIOUS change in overall circuit value - with potential radical or damaging results in vehicle operation - and erratic or intermittent contacts poorly done or suffering from the elements and old age can do the same...:pca1:

In all your travels have you or anybody else out there ever found a guide to all the grounding points on our truck so we know where to go looking for all these bolts to clean up.

Never seen any documentation of all the various grounding points - but there certainly are LOTS of them! And pretty amazing that even some DC uses are to points where there is minimal chance of a good contact even being made - such as the grid heater grounding lead I showed above!

Since I work with mobile Amateur Radio, I probably have done more grounding and scattered Radio Frequency Interference (RFI) work and elimination than most - and that as well as the MANY constantly surfacing issues related to electrical malfunctions and intermittents is what prompted this thread.

I know they are scattered all over the trucks and somtimes hard to find, so I'm hopin somebody has a schematic we could use. Maybe somebody with access to ALLDATA can print some off and post em.

The factory service manuals do give ground locations.

BOB

Another neat trick to verify connections of you electrical system...

Take a DVM (Digital Volt Meter) and hook the positive lead to the negative post of the battery and take the negative lead and follow the ground lead on you wiring.

If you DVM shows > 0.2 Volts at anytime then the lead you on right now has a weak connection and needs to be fixed...

This trick works for positive leads too...:U:

Michael, shouldn't the DVOM show battery voltage (>=12 V) if the positive lead is on the positive battery terminal, and the negative lead on a ground? Or, did I miss something?

Yea you did miss something...

NEG DVM LEAD ----> NEGATIVE POST ON BATTERY

POS DVM LEAD ----> TO OTHER END OF GROUND WIRE

Or you can check POSITIVES

POS DVM LEAD ----> POSITIVE POST ON BATTERY

NEG DVM LEAD ----> TO OTHER END OF POSITIVE LEAD

At no time should both DVM lead be in POS and NEG at the sametime. Always on a POSITIVE lead or always on a NEGATIVE lead. The measured voltage is the voltage loss down the wire. So if the reading is >0.2 Volts then you losing that from start to finish. So you back track down the lead at connectors and check again a find where the change from 0 volt to a high voltage. This is where the weak connection is at.

Battery post_______End of ground wire
0.0 Volts -----------> 0.2 Volts

As a matter of fact I learned this trick from a Honda Goldwing site. I had a bad ground that was causing a weak charge at the battery. Buit the trick work on all wiring... Cars, Truck, motorcycles... Etc.

Dern contacts messin' up my readin'.:argh:

Hmmm... Maybe thats why I wear glasses...:c:

http://i143.photobucket.com/albums/r...m/IMGP0050.jpg