quest. about my new tach dash. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BUXMAN66 · 12-23-2003, 05:30 AM

got me a new tach dash !! just need to figger out how the original (need to get one) style tach harness will hook up w/ my hei style of dizzy? will i need the harness or can i use a separate wire from the back of the tach (coil) to the hei, and use another wire from (12v) on back of tach, to a 12volt power source? or....does the 71-72 style tach harness have a plug for the hei style dist.? didn't they have hei on the 71-72 models...or was it still points ? thanks for any and all replies....

71Chev · 12-23-2003, 08:57 AM

If you are also converting from a idiot light dash to a full gauge dash you will have to make that conversion also for the gauge dash to work. If you already have full gauges you just need 2 wires for the tach. It was still points in 71-72. Just run it like you said. Run a wire from "coil"(on the tach) to the tach terminal on the hei and then a wire from the hot to a 12v source. Put a 5amp inline fuse in the power wire. 12ga wire is plenty.

BUXMAN66 · 12-24-2003, 03:23 AM

thanks for the reply ! the "hot" wire.....should it be constant,or should it be "keyed" power? does the power supply the light in the tach? if so, i would think it would need to be a "ignition on" or a "keyed" power source.thanks again.

71Chev · 12-24-2003, 04:49 AM

You want keyed power. The tach is illuminated by the other lights in the gauge panel, it doesn't have it's own light. You have a factory tach correct?

BUXMAN66 · 12-25-2003, 09:26 PM

yes, it's a factory tach . i just did'nt know that the factory tach.'s were back-lighted by the other "push-n-twist" lights in the dash....learn somethin' new every day!! thanks for clearing up the keyed power and constant power source question,also!! so, what exactly is the 12v power source for anyway?..... it's not like the actual tach has a motor in it that needs a power source....and the power source does not supply the lighting aspect of it...so what is it for?

BUXMAN66 · 12-25-2003, 09:33 PM

btw, to answer your previous question on the earlier post.... my factory dash was a idiot light dash, so obviously i needed to change over the wiring in the plug to accept the guage dash to function properly. (kudos to gmcpauls site on that project!!) so yes,....the wiring is completed, just need to slap the new panel in. the wiring on the tach was my only concern....

BUXMAN66 · 12-26-2003, 10:28 PM

ttt

**ScottH** · 12-26-2003, 11:17 PM

Hey, one of these days I will be doing the conversion you are working on. Can u tell me what u meant by "my factory dash was a idiot light dash, so obviously i needed to change over the wiring in the plug to accept the guage dash to function properly. (kudos to gmcpauls site on that project!!) " ?

Thanks.

SWEET7T · 12-27-2003, 12:59 AM

the '12V" that your talking about IS the 'keyed' power. Just plug or tap into a source on your fuse panel that is 'hot' when you turn the key on, and the other wire, as you already know, goes to your HEI....

BUXMAN66 · 12-27-2003, 01:55 PM

sweet....i know the 12v is the keyed power !!! but the question i'm asking and not getting a straight answer too is....what ..hell forget it!! i know how to hook it up now...... scotth,.. what i was refering to is that the truck i have was a factory idiot light dash truck.meaning the wiring harness to the dash is configured to run an idiot light dash and not to run a guage dash....the wiring in the factory harness for a guage dash has a different configuration in the pin's of the plug-in.run a search function on this subject or check out gmcpauls web-site under tech questions.

12-23-2003, 05:30 AM	#1
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	quest. about my new tach dash. got me a new tach dash !! just need to figger out how the original (need to get one) style tach harness will hook up w/ my hei style of dizzy? will i need the harness or can i use a separate wire from the back of the tach (coil) to the hei, and use another wire from (12v) on back of tach, to a 12volt power source? or....does the 71-72 style tach harness have a plug for the hei style dist.? didn't they have hei on the 71-72 models...or was it still points ? thanks for any and all replies.... __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

12-23-2003, 08:57 AM	#2
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	If you are also converting from a idiot light dash to a full gauge dash you will have to make that conversion also for the gauge dash to work. If you already have full gauges you just need 2 wires for the tach. It was still points in 71-72. Just run it like you said. Run a wire from "coil"(on the tach) to the tach terminal on the hei and then a wire from the hot to a 12v source. Put a 5amp inline fuse in the power wire. 12ga wire is plenty. __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear. Last edited by 71Chev; 12-23-2003 at 09:00 AM.

12-24-2003, 03:23 AM	#3
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	thanks for the reply ! the "hot" wire.....should it be constant,or should it be "keyed" power? does the power supply the light in the tach? if so, i would think it would need to be a "ignition on" or a "keyed" power source.thanks again. __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

12-24-2003, 04:49 AM	#4
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	You want keyed power. The tach is illuminated by the other lights in the gauge panel, it doesn't have it's own light. You have a factory tach correct? __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear. Last edited by 71Chev; 12-24-2003 at 05:09 AM.

12-25-2003, 09:26 PM	#5
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	yes, it's a factory tach . i just did'nt know that the factory tach.'s were back-lighted by the other "push-n-twist" lights in the dash....learn somethin' new every day!! thanks for clearing up the keyed power and constant power source question,also!! so, what exactly is the 12v power source for anyway?..... it's not like the actual tach has a motor in it that needs a power source....and the power source does not supply the lighting aspect of it...so what is it for? __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

12-25-2003, 09:33 PM	#6
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	btw, to answer your previous question on the earlier post.... my factory dash was a idiot light dash, so obviously i needed to change over the wiring in the plug to accept the guage dash to function properly. (kudos to gmcpauls site on that project!!) so yes,....the wiring is completed, just need to slap the new panel in. the wiring on the tach was my only concern.... __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

12-26-2003, 10:28 PM	#7
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	ttt __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

12-26-2003, 11:17 PM	#8
ScottH Senior Member Join Date: Sep 2002 Location: Hampstead, NC Posts: 8,190	Hey, one of these days I will be doing the conversion you are working on. Can u tell me what u meant by "my factory dash was a idiot light dash, so obviously i needed to change over the wiring in the plug to accept the guage dash to function properly. (kudos to gmcpauls site on that project!!) " ? Thanks.

12-27-2003, 12:59 AM	#9
SWEET7T Try spinnin 4 rear tars Join Date: Sep 2003 Location: Salt Lake City, Utah Posts: 757	the '12V" that your talking about IS the 'keyed' power. Just plug or tap into a source on your fuse panel that is 'hot' when you turn the key on, and the other wire, as you already know, goes to your HEI.... __________________ SWEET7T 1970 C10, 2wd, LB, 307/TH350/3.08. PS, PB

12-27-2003, 01:55 PM	#10
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	sweet....i know the 12v is the keyed power !!! but the question i'm asking and not getting a straight answer too is....what ..hell forget it!! i know how to hook it up now...... scotth,.. what i was refering to is that the truck i have was a factory idiot light dash truck.meaning the wiring harness to the dash is configured to run an idiot light dash and not to run a guage dash....the wiring in the factory harness for a guage dash has a different configuration in the pin's of the plug-in.run a search function on this subject or check out gmcpauls web-site under tech questions. __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?



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