MACS Monthly Newsletter - 2020 - MAY3

AES Wave / GM

Figure 4: Whether you follow this exact color-coding key or make up your own system, breaking down a complex schematic by color coding the
circuits by their functions can become a powerful "magnifying glass" to assist you in diagnosing the vehicle!
sis (a.k.a. trial and error) whether to tape the schematics end to end like a large folding paper map, or staple
them together in logical order like a paper road atlas.
You could simply look at the schematic on your PC or
tablet screen and move the schematic around with your
finger, but that's not nearly as effective as getting the entire schematic blown up (enough to see all the details)
but still on one large screen or document. Continuing
the road map analogy, for the younger techs reading this
who have always used a map on your phone, you'll have
to admit that unless you have a GPS feature along with
mapping software to move that magnified section of the

3. Both fans on high speed
Looking further at the schematic we can determine
since one of the three relays which apparently feeds power to the right cooling fan motor is labeled "Cooling Fan
Low Speed Relay" that the right cooling fan motor may
run at two speeds - low and high.

Maze to Roadmap:
Mile Markers - Knowing Electrical Component
Locations

If you're a baby boomer, once upon a time when you
first learned to read a paper roadmap, you may recall
learning a bit about those letters and numbers along the
top and sides of a roadmap. On the back of most maps
there was a list of cities with an alphanumerical coordinate such as "D4" next to each town's name. Next, on
the actual map you found where the "D" row intersected
with the "4" row to locate town. Without those coordinates, finding some smaller towns was like the proverbial needle in a haystack. The Milton Bradley's game of
"Battleship" worked much the same way. I apologize if
you're too young to remember either of those!
Many OEMs number their electrical schematic components such as grounds, connectors and splices in a logical
order similar to those old paper roadmaps. The 100 series
are under the hood. You'll find 200 series under the dash
and so forth. Even the right and left doors have unique
coordinates to assist you in locating them on the vehicle
(Figure 5).

Figure 5: You might wonder why all OEMs label electrical
components ranging from connectors, grounds, grommets
and splices as logically as GM as shown in this illustration.

Maze to Roadmap:
Step 1 - Print Out Schematic

map as you travel along, the electronic map is not very
helpful. You can only see a little bit of the details at
one time. The same is true with a schematic on a
computer screen.

If the wiring schematic is spread out on multiple pages,
then by all means, print them all (on several pages) and
then organize them. You can judge on a case by case ba-

May 2020

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MACS Monthly Newsletter - 2020

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