Need instrument cluster help!! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jonboy · 07-23-2004, 11:58 AM

I need some help with the wiring plug on the tach dash I got for my Blazer. I have a 77, and have a 79 cluster. I have a mechanical gauge to fit the hole, so that is not a big convern. My question is about the wiring for the main cluster plug. Does anyone have a diagram for the plug, so I can repin what I have and make it work? I have the tach wiring figured out, just need help with the main plug. Thanks in advance!

NeCrOmAnCeR · 07-23-2004, 01:47 PM

I just traced the circuits on the old dash, then for the new one. Move the wires for fuel sender from the old position to the new, then temp, etc.... Just draw a diagram of the connector, labeling with colors and circuit function, then move the wires to the correct position for the new dash. Good luck!!

Jonboy · 07-23-2004, 01:53 PM

I was going to do that, but I am lazy. Looks like that may be next week's project.

Grim Reaper · 07-23-2004, 02:17 PM

BIG TIME MAJOR ELECTRICAL CHANGE FOR 78.

78 was the first year for the blade style fuse box. Oil presure went electric that year, gas door added, rear seat foot well and fold and tumble rear seat first year as well. LOTs of firsts. Your going to have to trace down the harnesses. Best place to start is your local library and see if the have the year spicific repair manuals on Microfisch. It's 10 cents a copy at mine.

**Captkaos** · 07-23-2004, 02:35 PM

Check a Haynes Manual for the trucks. That is what I use.

Jonboy · 07-25-2004, 10:14 PM

Ok, I got the main plug wired, and eerything seems to work. Next question: where do I hook up the power lead for the tach? I put it to 12V switched power on the fuse box, and the tach needle swung 360 degrees. What did I do wrong there? I ran a wire from the "tach" port on the distributor cap, and grounded the black wire to the body.

NeCrOmAnCeR · 07-26-2004, 10:09 AM

Does it work with the engine running? If not sounds like the tach needs to be fixed. Do you have any other ignition system besides stock? (MSD etc..)

Jonboy · 07-26-2004, 10:51 AM

No, it's an HEI. I was thinking maybe my ground is not the best. I am going to try to fix that, and see what happens.

Greg Carter · 08-02-2004, 11:28 AM

Jonboy,

Any progress with your tach? I just bought an '82 and the factory tach does the same thing. I measured the lead labled "12v" on the instrument cluster on the tach connector and there was nothing there, 0v. So I jumped 12v to it and the needle just swung all the way to max. I traced the wire (pink on my truck) all the way back to the fuse box and it is 0v there to. All the fuses are good. Can't figure this out.

Jonboy · 08-02-2004, 11:31 AM

I haven't done anything to it yet. I tried to put the stereo in all weekend, and ended up doing everything else but that. I just left it unhooked for the time being.

07-23-2004, 11:58 AM	#1
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Need instrument cluster help!! I need some help with the wiring plug on the tach dash I got for my Blazer. I have a 77, and have a 79 cluster. I have a mechanical gauge to fit the hole, so that is not a big convern. My question is about the wiring for the main cluster plug. Does anyone have a diagram for the plug, so I can repin what I have and make it work? I have the tach wiring figured out, just need help with the main plug. Thanks in advance! __________________ 1974 Jimmy- 5.3/4L80e/NP241

07-23-2004, 01:53 PM	#3
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	I was going to do that, but I am lazy. Looks like that may be next week's project. __________________ 1974 Jimmy- 5.3/4L80e/NP241

07-23-2004, 02:17 PM	#4
Grim Reaper Registered User Join Date: Jul 2001 Location: Atlanta GA Posts: 1,704	BIG TIME MAJOR ELECTRICAL CHANGE FOR 78. 78 was the first year for the blade style fuse box. Oil presure went electric that year, gas door added, rear seat foot well and fold and tumble rear seat first year as well. LOTs of firsts. Your going to have to trace down the harnesses. Best place to start is your local library and see if the have the year spicific repair manuals on Microfisch. It's 10 cents a copy at mine. __________________ Grim-Reaper 70 Pontiac LeMans Sport Convertible, worlds longest resto in progress Looking for 71-72 2wd Blazer or Jimmy Project

07-23-2004, 02:35 PM	#5
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Check a Haynes Manual for the trucks. That is what I use. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

07-25-2004, 10:14 PM	#6
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	Ok, I got the main plug wired, and eerything seems to work. Next question: where do I hook up the power lead for the tach? I put it to 12V switched power on the fuse box, and the tach needle swung 360 degrees. What did I do wrong there? I ran a wire from the "tach" port on the distributor cap, and grounded the black wire to the body. __________________ 1974 Jimmy- 5.3/4L80e/NP241

07-23-2004, 01:47 PM	#2
NeCrOmAnCeR Registered User Join Date: Feb 2004 Location: Hodgenville, Ky Posts: 735	I just traced the circuits on the old dash, then for the new one. Move the wires for fuel sender from the old position to the new, then temp, etc.... Just draw a diagram of the connector, labeling with colors and circuit function, then move the wires to the correct position for the new dash. Good luck!!

07-26-2004, 10:09 AM	#7
NeCrOmAnCeR Registered User Join Date: Feb 2004 Location: Hodgenville, Ky Posts: 735	Does it work with the engine running? If not sounds like the tach needs to be fixed. Do you have any other ignition system besides stock? (MSD etc..)

07-26-2004, 10:51 AM	#8
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	No, it's an HEI. I was thinking maybe my ground is not the best. I am going to try to fix that, and see what happens. __________________ 1974 Jimmy- 5.3/4L80e/NP241

08-02-2004, 11:28 AM	#9
Greg Carter Registered User Join Date: Aug 2004 Posts: 3	Jonboy, Any progress with your tach? I just bought an '82 and the factory tach does the same thing. I measured the lead labled "12v" on the instrument cluster on the tach connector and there was nothing there, 0v. So I jumped 12v to it and the needle just swung all the way to max. I traced the wire (pink on my truck) all the way back to the fuse box and it is 0v there to. All the fuses are good. Can't figure this out.

08-02-2004, 11:31 AM	#10
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	I haven't done anything to it yet. I tried to put the stereo in all weekend, and ended up doing everything else but that. I just left it unhooked for the time being. __________________ 1974 Jimmy- 5.3/4L80e/NP241



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