Hey, I have searched but did not find this topic. I did this upgrade on my gmt800 and noticed a difference all around, bc i think the factory put bare minimal effort in grounding these trucks.
So i've got this 1/0 wire, 1/0 - 3/8 copper lugs, heatshrink, a 300 ANL fuse, wire cutter, and hammer crimper. I plan on cleaning up factory grounds too ... a little grinding/sanding, dieclectric, and spray with black tractor paint. Anyone have knowledge or tips for doing the big three upgrade in a gmt400 before i get started? Thanks!
Here's what I've done (but I don't have my notes handy, so from memory) and probably a few others on GMT400 have done.
Be methodical:
- Get a voltmeter / DVM. Cheap ones can be had for... cheap. I use a Fluke 77.
- Connect the DVM's black lead firmly to the engine block / alternator
- Get a pad of paper and make some columns, labeled
(i) battery gnd
(ii) frame (at ground strap, passenger's side)
(iii) body (at ground strap connection, passenger's side)
(iv) alternator output
(v) battery +
(vi) terminal block (driver's side at the fuse holder)
(vii) another body location, you pick (for comparison to (iii) above, as a sanity check)
- Start measuring the voltage at those locations with the DVM's red lead, under at least the following situations:
(a) engine off
(b) engine on, RPM 1200, HVAC off, all lights / accys off
(c) (ditto) headlights on high
(d) other variations as one sees fit, e.g., blower high, compressor on, high-watt stereo cranked, etc.
(e) add your particular situation here
When done, grab a beer, start admire your research and study the measurements.
Look where the larger voltage drops are happening, and focus on those locations for "upgrade" with heavier gauge wire.
I suspect you'll find that the biggest bang-for-the-buck is "beefing-up" the lead from the alternator to the terminal block (driver's side fuse holder) and battery, as the OE wire isn't really that heavy and it's a LONG length of wire.
Otherwise, "freshening-up" some of the ground connections may be required to reduce voltage drops, but of course the voltage measurements will tell you where you need to focus. You may find, for instance, the ground strap from the frame to the engine has excessive voltage across it and needs freshening... or not.
Then, after you've made changes, duplicate your measurements as appropriate and make note of the improvements. Save all the notes, so that you have them at a later time should there be some electrical issue needing attention.
Crack another beer and reflect what you've learned, the methods you employed, and the improvements you've made
PS: If you're curious, get a DC-current capable clamp ammeter (e.g., Fluke 36, which I use) and measure the current in the various connections (alternator output wire, ground straps, wherever) while you're measuring voltages. It may give you additional perspective.
PPS: I found both meters on eBay just now for about $35 (Fluke 77) and $40 (Fluke 36). Using both meters together allows one to measure both the voltage and current simultaneously.