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Discussion Starter #1
Need help troubleshooting the cluster on my 70. The Speedo doesn't illuminate. I replaced the headlight switch, hoping that, that would take care of it. Switch is nice and crisp now but the dash still doesn't light up. The only things that lit, before and after the new switch, are the climate control panel, and my auxiliary gauges, Tach on the column, and Oil/Temp/Batt gauges mounted beneath the dash.

Not sure if it could be a wiring issue? The printed circuit on the back of the cluster? I've checked all the bulbs and they're good, but I did notice that the cluster pulls away from the housing when you pull the bulb out, could that be a problem? If so, where do you source a new circuit? I've looked on Ebay for even a used Sweep cluster, but can't find any.

Any help would be appreciated.

Thanks
 

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A new sweep dash printed circuit is going to be tough to find. All I ever see is reproduction printed circuits for SS dashboards because people want to upgrade to those.

Rick

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the Instrument light circuit is a little different,
power comes from the
Courtesy circuit and Tail light fuse/circuit and Instrument light fuse/circuit..

this is a later model diagram,, but its close..
link> Light Switch

see if you have power to the Inst Lamp fuse or grey wire to the dash pod,,
go from there,, youll know if you need to look forward or backwards..

check the ground too..
 

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@A. McGovern
This thread will have your answer and more info.

1970-72 sweep dash - Name the Idiot Lights
 

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Discussion Starter #5
A new sweep dash printed circuit is going to be tough to find. All I ever see is reproduction printed circuits for SS dashboards because people want to upgrade to those.

Rick

Sent from my SM-G965U using Tapatalk
Yeah I've seen that too. I wish they would reproduce it. Would make life so much easier for those of us that don't have the cash to convert to the SS style.
 

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Discussion Starter #6
the Instrument light circuit is a little different,
power comes from the
Courtesy circuit and Tail light fuse/circuit and Instrument light fuse/circuit..

this is a later model diagram,, but its close..
link> Light Switch

see if you have power to the Inst Lamp fuse or grey wire to the dash pod,,
go from there,, youll know if you need to look forward or backwards..

check the ground too..
Thanks. I went out early this morning, I have power all the way up to the socket. But the socket isn't grounding properly. I need to find out where the ground goes. It disappears into the wire loom.
 

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Discussion Starter #7
@A. McGovern
This thread will have your answer and more info.

1970-72 sweep dash - Name the Idiot Lights
Thanks for the link. A lot of good information in there. Haven't fully read through it yet. I need to figure out where the ground for the instrument light pigtail goes. I have power but intermittent ground.
 

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Sounds typical. The gray or black wire in the first pig tail break. That connection is not reproduced. If it is the ground you might try running a ground wire back to the ground behind he dash were the light switch grounds. That may work, or help identify the socket wires are having problems. There is a fix in my thread above that shows how to "weld" to the circuit board and get another of the 2 thru 5 sockets to replace the pigtail socket.
 

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IIRC ?? 3rd gen has more than 1 ground connection on the dash..

kinda like what Bear said
find the black wire from the headlight switch, see where it goes,,
see if they tie together, and where they go..

look around on the dash frame, kick panel, firewall,
for black/ground wire/s screwed down..
 

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Seems like I remember there being a ground from the dash to the top of the pedal assembly.
Have to start the cluster back in and stop part way and run the screw into the pedal assy..
If I'm wrong it will be the first time since 2:35PM
 

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The ground strap that I mentioned might be for the round gauge dash.

I looked at my multicolor 18 X 24 inch laminated electric diagram and it looks like for our sweep dash, that the ground goes to the radio and then to a ground.

Yet in the diagram on ElCaminoCentral site, it shows it going straight to ground.
Diagrams for all years of El Caminos found on this link below.
 

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Discussion Starter #13
IIRC ?? 3rd gen has more than 1 ground connection on the dash..

kinda like what Bear said
find the black wire from the headlight switch, see where it goes,,
see if they tie together, and where they go..

look around on the dash frame, kick panel, firewall,
for black/ground wire/s screwed down..
The ground for the light switch goes to a ground strap that is fixed to the dash. I did find one loose ground wire coming off the harness, screwed it down to the same ground strap as the light switch. No change.
 

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Any chance the dash is unbolted hanging free and not grounded back to car, while the aftermarket gauges are grounded back to car?
 

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Discussion Starter #16
The ground strap that I mentioned might be for the round gauge dash.

I looked at my multicolor 18 X 24 inch laminated electric diagram and it looks like for our sweep dash, that the ground goes to the radio and then to a ground.

Yet in the diagram on ElCaminoCentral site, it shows it going straight to ground.
Diagrams for all years of El Caminos found on this link below.
I looked at that ground strap and although it states that it's for an SS dash, it looks identical to what is on my dash right now. I've also ordered one of the electric diagrams from the second link you listed. I've narrowed the problem down to a loose ground within the instrument light plug. I don't know if I can somehow tighten up the ground pin without destroying the plug. I can't seem to find a replacement plug either. I was thinking I could cut the old one off, and solder on a new one.
 

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Discussion Starter #18
It will be easier to use Justin's fix in post #35 of the thread in the link.
That seems like an effective fix. Luckily, I won't have to do that. I went out early this morning after thinking about the plug late last night. I was able to get a precision screwdriver in the plug to release the pin, I lightly sanded the contacts thinking that over the years the grime caused it to lose solid connection. Turns out that the prong that holds the pin in the plug has likely worn a relief in the plastic, causing it to drop back and lose contact. After a little thought, I figured I'd just solder the two tabs together in hopes that would fix the issue. After letting it cool, I crossed my fingers and pulled the headlight switch on, and the light turned on immediately. I tried it a few more times cycling the switch on and off while moving the plug and wires around. Didn't turn off, so I carefully returned it to it's rightful spot in the instrument panel. All lights illuminate and it's good to go!
 

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And now you can see the fuel gauge when it is dark outside without using a flashlight.
 
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