1984 C20 Fuse Panel and Harness examination

[dougbert]

I found a very useful feature of the Wiring Manual is the Electrical Circuit Identification for Wiring Diagrams.

I printed the first 7 pages of the 1984 manual for my 1984 rig. This lists the Circuit Number, then Circuit Color and Circuit Name or Function. It really, really helped understand the diagrams

Diagrams for several years are linked at http://www.gmsquarebody.com/forum/showthread.php?t=14498 choose the year you want. These documents are PDFs and I have downloaded them. Thanks to hatzie for posting them

dougbert

 

[HotRodPC]

I found a very useful feature of the Wiring Manual is the Electrical Circuit Identification for Wiring Diagrams.

I printed the first 7 pages for my 1984 rig. This lists the Circuit Number, then Circuit Color and Circuit Name or Function.

Diagrams for several years are linked at http://www.gmsquarebody.com/forum/showthread.php?t=14498 and select the 1984. Also there are other years. These documents are PDFs and I have downloaded them. Thanks to hatzie for posting them

dougbert

Sorry, I thought you knew those were there. I hope he keeps those hosted. He doesn't visit us very often, but he not only posted those, he's hosting those so they could disappear at any time. If you want them, I do suggest you download them to keep them on your hard drive somewhere.

 

[chengny]

This pair connects to the driver's side door jamb switch ( note that the LH side switch has two tabs).

Along with another one in the RH door jamb, the white lead provides one of two ground legs for the courtesy/dome lighting circuit.

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The tan lead is the ground leg for the "Key is In The Ignition" warning chime. There is always power to the positive side of the warning chime (shared with Fasten Seat Belt warning). With the key in the lock cylinder, this switch is closed:

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and the tan wire runs runs from the switch to the LH jamb switch. So if the key is in the ignition lock cylinder, and the LH door is opened....ding,ding.

 

[dougbert]

I am revisiting this thread because I am adding Jabin Wood's power window harness to my rig and I really wanted to understand the fuse block model. It has always confused me until I found the upcoming web page. I have found a couple more pics from there, that really describes the layout of the fuse block VERY WELL

In post #4 above I attached a PDF with the fuse block labeled in a 8x8 grid, where columns were A (at the left), B, C, ...., H

Rows were 1 (at the top), 2, 3, ..., 8

I will post an updated table legend in another post below

I found the following information at this website. Please go there for more info that I have not copied over:

http://www.rowand.net/Shop/Tech/GMATOStyleFuseBlock.htm

Quote:

Here are two schematic drawings of this type of GM fuse block.

The first is as I scanned it from a 1978 Chevy Truck wiring manual. Specifically it comes from the diagram for the G bodies (the vans) - apparently the regular trucks did not switch to the ATO style fuse block until later - something to be aware of when hunting in the junkyards.

The second is the same diagram with markup to make it clear where each fuse is, what it feeds, along with which end of the fuse is the feed and the output, and the separate extra "plug in" terminals for various add-on options.

The red shapes indicate each fuse and it's associated output terminals.
The red dots are the input to each fuse,

the light green dots are the output from each fuse, and

the blue dots are extra "plug in" terminals.

The lone dark green dot is a fuse location that can accept a plug-in circuit breaker or a fuse, but still feeds it's power out the back of the fuse block and into the extra "plug in" terminal associated with that fuse location.

The lone purple dot is a high-power output terminal that is intended to be used with a special circuit breaker and output wire assembly.

endquote

that lone purple dot is F2, and meant to feed power windows and tail gate window, circuit #76.

Position H6 is for power door locks and rear WDO Defrost, circuit #60

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gauge of wire for common wire runs, and incoming output circuits

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The diagram (which I have studied A LOT) below is a repeat picture from post #7. It is a factory diagram which diagrams the fuse block. In the lower left of the diagram are GM part numbers (most of which are discontinued) for connectors that go to the various labeled (A, B, C ....) positions, referred to in the diagram (NOT my A1 references).

The tables are in the lower left of the diagram

Left most table are the connector mapping to part number. Full part number in first line, then just the difference in part number on subsequent rows, as they are near each other

Right most table are fuse part numbers, with amp rating and color

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[AuroraGirl]

I am revisiting this thread because I am adding Jabin Wood's power window harness to the rig really wanted to understand the fuse block model. I have found a couple more pics to describe the layout of the block

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Are the first two power and grounds... or..?

 

[dougbert]

Are the first two power and grounds... or..?

okay I updated my post with some more information:

the first pic is a frontal diagram of the fuse block as you would see it as you looked at it under the dash

the second pic is a rear diagram of the same block as you would see it looking at from firewall looking back to the seat. It shows COMMON connections between position. For example common BATTERY HOT leads, or common TAP points from one fuse, like the IGN series

The first pic labels FUSE positions, and what positions are incoming fuse (RED = hot) and outgoing circuit (GREEN). Blue positions are additional TAPS the come from the nearby fuse.

For reference there are 8 columns and 8 rows of position and
I label columns of position A, B, .... H (left to right)
and label rows 1, 2, 3, .... 8 (top to bottom)

For example, position E4 is a red incoming source and D4 is the fused outgoing circuit. The outgoing circuit goes "back" behind the fuse block

Another is B5 is incoming red source and A5 is a green outgoing circuit toward the back of the block. There are 3 TAP positions at A3, A4 and A6 that are common with A5.

There are 3 states:

ALWAYS ON like TAPS E7 and E8 which are in common with Horn circuit at E6
IGNITION (key on) like TAPS A3, A4 and A6, on at RUN and START key positons
ACCESSORY like TAP D3, on at RUN and ACCESSORY key positions, radio, power windows, etc

does that help. If not, can you be more specific to what you are referring to?

 

[AuroraGirl]

okay I updated my post with some more information:

the first pic is a frontal diagram of the fuse block as you would see it as you looked at it under the dash

the second pic is a rear diagram of the same block as you would see it looking at from firewall looking back to the seat. It shows COMMON connections between position. For example common BATTERY HOT leads, or common TAP points from one fuse, like the IGN series

The first pic labels FUSE positions, and what positions are incoming fuse (RED = hot) and outgoing circuit (GREEN). Blue positions are additional TAPS the come from the nearby fuse.

For reference there are 8 columns and 8 rows of position and
I label columns of position A, B, .... H (left to right)
and label rows 1, 2, 3, .... 8 (top to bottom)

For example, position E4 is a red incoming source and D4 is the fused outgoing circuit. The outgoing circuit goes "back" behind the fuse block

Another is B5 is incoming red source and A5 is a green outgoing circuit toward the back of the block. There are 3 TAP positions at A3, A4 and A6 that are common with A5.

There are 3 states:

ALWAYS ON like TAPS E7 and E8 which are in common with Horn circuit at E6
IGNITION (key on) like TAPS A3, A4 and A6, on at RUN and START key positons
ACCESSORY like TAP D3, on at RUN and ACCESSORY key positions, radio, power windows, etc

does that help. If not, can you be more specific to what you are referring to?

It does. I have an 1980(different of course) but was just curious what your homemade color coding was supposed to represent. if you guys are compiling fuses. I can show you a 1980 something that had horizontal side markers and a manual trans and a 1978 K10 auto trans(with a lot of extra equipment) and a 1980 k25 manual trans. But, keep in mind, 78 had glass fuses.

 

[dougbert]

It does. I have an 1980(different of course) but was just curious what your homemade color coding was supposed to represent. if you guys are compiling fuses. I can show you a 1980 something that had horizontal side markers and a manual trans and a 1978 K10 auto trans(with a lot of extra equipment) and a 1980 k25 manual trans. But, keep in mind, 78 had glass fuses.

in the updated post, I quoted the author of the pictures on what the colors do mean. More information at his website

I think it would be great to get as many various years as we can, but each would be in their own thread. This thread is the C20 for 1984


read the article at http://www.rowand.net/Shop/Tech/GMATOStyleFuseBlock.htm

because the author swaps out the older fuse blocks with newer ones for reasons he gives in the article

 

[dougbert]

Here is my PDF, which is my attempt to describe the layout, with some better descriptions of what the 8x8 fuse block position ares, at least for this C20 block. Base from the website above. I recommend downloading his website for your personal use in case his website is lost.

 

[dougbert]

I also have found some TAP connectors with pigtail

Always on: https://www.repairconnector.com/gm-fuse-block-tap-power-always-on/

IGN on: https://www.repairconnector.com/gm-ignition-cavity-fuse-block-tap-clear/

Of course I emptied their supply of 2 each, but hopefully they will re-order for their inventory

I also ordered the following kit: https://www.dragracecarparts.co/ame...power-tap-connector-and-terminal-kits-500429/

which there are a couple of sources for, JEGS, SUMMIT and this dragracecarparts place

dougbert

 

[Snoots]

Thank you for the GREAT info and locations!

 

[dougbert]

here is a picture of a fuse block WITH two circuit breakers, upper right silver box and center right, another circuit breaker.

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Circuit breaker is:

GM Part #1252240

I ordered one off of Ebay

 

[Snoots]

I keep those on hand. I'd have gladly sent you one. They're used on any early GM with Power Windows.

 

[AuroraGirl]

Ive got a few of those from an 88 lesabre. and i know this is for 1984 fuse panel, im just saying what i have.

 

[dougbert]

I keep those on hand. I'd have gladly sent you one. They're used on any early GM with Power Windows.

ah, thanks. I will probably need a second one, if things work out - see below

I am adding power windows. What I am missing is the female receiver in the upper right position. The lower ACCY position there is a receiver and I can put the breaker there and use the TAP point.

I am going to experiment with the spare C20 block to see what it would take to add new receiver clips in the back of the block. If I can doing it then I think I will do it on the block in my rig

I mean, that would add 5 more circuits out the back and 3 more TAP points, for 8 more circuits - that would be great. Will document that on this thread

The author of the web page above which I reference, that was his intent for upgrading glass fuse type of blocks