reading schematic of fuse panel - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 25 (permalink) Old Aug 11th, 19, 10:38 PM Thread Starter
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phil
 
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reading schematic of fuse panel

Hi,

Working on a 66 chevelle convertible...

I've got a dead short that immediately blows the second from the bottom fuse(yellow arrow) in the photo. No taillights, brake lights, instrument cluster/interior lights. The lamps and bat fused(circled in yellow) also have no power with that fuse out.

A photo of the wiring diagram is also attached for the fuse block.
But how do I know which fuse belongs to which color wire on the diagram? There are 6 fuses but that diagram shows 17 squares with circles inside? Please help me understand how the diagram corresponds to the actual fuses.

Lastly, the 3rd photo shows what I think is the cable going to the rear taillights. I disconnect the connector there and still problem exists so I can rule out the wiring back in the trunk, correct?

Thanks for your help!
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post #2 of 25 (permalink) Old Aug 11th, 19, 11:20 PM
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Re: reading schematic of fuse panel

That fuse protects a hot battery feed to several circuits. Check for shorts in courtesy lamp sockets, cigarette lighter, light switch, dimmer switch, parking lights and headlights. Does the fuse blow with the red wires on the bat fused terminal disconnected?

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post #3 of 25 (permalink) Old Aug 11th, 19, 11:42 PM Thread Starter
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Thanks
cigarette lighter, high beams
and headlights work. Parking lights don't but front turn signals both do.
Disconnected bat fused 2 red wires and still blows fuse.


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post #4 of 25 (permalink) Old Aug 11th, 19, 11:57 PM
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Re: reading schematic of fuse panel

Use a meter...they are magical....

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post #5 of 25 (permalink) Old Aug 12th, 19, 12:17 AM
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Re: reading schematic of fuse panel

Quote:
Originally Posted by plcguru View Post
Thanks
cigarette lighter, high beams
and headlights work. Parking lights don't but front turn signals both do.
Disconnected bat fused 2 red wires and still blows fuse.
Sounds like you have a short in your forward light harness. One common place to get a short is at the back of the light housing where the wires connect. If not there follow your wire harness up to the back of the fuse box.
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post #6 of 25 (permalink) Old Aug 12th, 19, 1:35 AM
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Re: reading schematic of fuse panel

There is a wire that runs from the fuse box taillights fuse up to the headlight switch. I think it is orange on a 66. This provides fused power to the taillights and parking lights. The parking lights and tail lights should come on when you pull the headlight switch out 1 position. When you pull to the second position, the headlights come on, but the parking lights turn off. This parking light scheme is for pre 68 only. The wire from the headlight switch to the parking lights is purple. It gets power from the orange wire from the fuse box. The taillights are fed from the same orange wire, but through the switch, they connect to the taillights via a separate brown wire. After the switch the parking lights and tailights are split into separate circuits fed from the same orange wire.

The power for the headlights comes from a red wire running from the 4 way connector or horn relay buss bar (depending on year). There is no fuse in that line and no fuse in the fusebox for headlights. The headlight switch actually has a circuit breaker in the switch to protect the headlight circuit.

Earlier I spoke too soon by saying your issue is in the forward light harness, it may also be located in the tail light harness or at the taillights themselves. I'm not sure that unplugging that connector will disconnect the tailights from the switch, so you can make that determination.

I blew this out quick from memory, hope it's 100% correct. Follow your wiring diagram and you should be able to make heads or tails from my post.

Last edited by DUTCH MAX HEADWORK; Aug 12th, 19 at 1:57 AM.
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post #7 of 25 (permalink) Old Aug 12th, 19, 2:24 AM
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Re: reading schematic of fuse panel

Almost forgot. That orange wire that feeds the headlight switch for the taillights and parking lights also feeds the rheostat power which feeds the green wire from the headlight switch to the fuse box fuse marked instr lts. From there it goes to a gray wire that feeds the dash/gauge lights. So a short in the green wire will also take out the taillights fuse.
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post #8 of 25 (permalink) Old Aug 12th, 19, 1:20 PM
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Re: reading schematic of fuse panel

Phil,

From what I have seen in your first post with the picture of the front of your fuse block and then the colored diagram picture, things are not matching up. I have a feeling the color diagram you have is incorrect and incomplete in the area of the accessory circuits.

On the top fuse in the picture of the actual fuse block, this is for the radio but on the color diagram is shows no connection. The second fuse down from the top is for the wipers and on the color diagram, here it shows a connection.

Another issue I see is on the battery circuit labeled "C" and "D" in my below picture is your fuse block shows three "D" terminals but the color diagram shows only 2 ?.

Anyway, below is how I think things are related between the fuse block and the color diagram:





Also on your fuse block, on the face on the right upper area there is a stenciled on white number. Could you take a clear picture of that and post it ?. I'm just wondering what you have is what I have on a donor harness. In my above picture the lettering is: CHEV.4282-J and this is what I'm wondering might be on yours.

Jim
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post #9 of 25 (permalink) Old Aug 12th, 19, 9:38 PM Thread Starter
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Re: reading schematic of fuse panel

Thanks guys!
If there's no rain tomorrow I'll dig in deeper then...
Seems I should focus on the orange and green wires.

Jim, looks like you're right about the fuse box... mine has 4282 in the upper right corner as well so I guess not the same exactly as the diagram I posted. I guess that also explains why I couldn't understand it.
For reference, I'm using a wiring diagram I purchased from here:
https://www.classiccarwiring.com/196...iring-diagram/

Anyway, I'll dig deeper looking for a short but please let me know if any advice on how to best quickly(or even slowly) find it as I'm a noob to short finding.

Thanks again,
Phil
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post #10 of 25 (permalink) Old Aug 12th, 19, 9:43 PM Thread Starter
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phil
 
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Re: reading schematic of fuse panel

Quote:
Originally Posted by pnugene View Post
That fuse protects a hot battery feed to several circuits. Check for shorts in courtesy lamp sockets, cigarette lighter, light switch, dimmer switch, parking lights and headlights. Does the fuse blow with the red wires on the bat fused terminal disconnected?
Yes, if red wires on bat fused terminal are disconnected I have the same issue.
Thanks,
Phil


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post #11 of 25 (permalink) Old Aug 12th, 19, 9:48 PM
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Re: reading schematic of fuse panel

Have you looked at the back side?

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post #12 of 25 (permalink) Old Aug 12th, 19, 9:58 PM Thread Starter
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Re: reading schematic of fuse panel

Quote:
Originally Posted by Peewee0413 View Post
Have you looked at the back side?

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No, I have not but seems like I should. Thanks


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post #13 of 25 (permalink) Old Aug 12th, 19, 10:22 PM
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Re: reading schematic of fuse panel

Here are the factory manual schematics and the colorized one.

Thanks, photosuckit. They couldn't put their damn logo at the top or bottom of the page, they have to put it SMACK in the middle.

https://www.chevelles.com/forums/27-...mps-fuses.html
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post #14 of 25 (permalink) Old Aug 12th, 19, 10:36 PM
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Re: reading schematic of fuse panel

Quote:
Originally Posted by davewho1 View Post
Here are the factory manual schematics and the colorized one.

Thanks, photosuckit. They couldn't put their damn logo at the top or bottom of the page, they have to put it SMACK in the middle.

https://www.chevelles.com/forums/27-...mps-fuses.html
The trick there is to click on the picture, it takes you to photo bucket and you down load it. Then you can enlarge it and be a happy camper.

I wish I had a picture of the full page so I didn't have to flip between pages a hundred times to figure out where the wires lead......hint hint.
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post #15 of 25 (permalink) Old Aug 12th, 19, 10:47 PM Thread Starter
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Re: reading schematic of fuse panel

Yep, that's the colorized one I'm using. Here it is as a single page.
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