Tach Test? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Ironhorse** · 03-29-2002, 08:19 PM

Can someone with a factory dash tach tell me how to test mine for operation before I put it in the new bezel and then in the truck? Have the tach, fact. GM printed circut, and the original harness. Heavy red wire with two clips or connectors, one has short pigtail connector and then a connector.(12 Volt power which hooks to 12 volt source unfused at fuse block), heavy brown wire (Hook to Coil Positive or Tach port on HEI) and then what? Does the tach use a ground? There is a threaded stud or attachment above the connections on the back of the tach.
'Preciate any help before I smoke test this thing. Got lucky couple years ago and found it in a truck at a 'yard for $15 for complete dash. Just been waiting until truck gets a complete re-build before I put it in. Thanks for any and all help.

------------------
1971 Chevy 1/2T 4x4 LWB 350v-8
Wellington, Ks

71Chev · 03-29-2002, 10:04 PM

The tach is grounded through the metal gauge housing. The case is grounded through the wire harness. To test it with out pluging in the dash harness, you have to hook up a ground wire to the case and the dash, and hook up the hot to the tach and to the distributer.

------------------

71 Chevy CST Long Fleet 350/350/3.07 leaf rear.
Email: 67-72truckparts@nanosecond.com

Rod · 03-29-2002, 11:08 PM

I just hold the metal case of the cluster against the rad cradle... use the tach harness to supply the power and put the brown wire to the distributor. Rev it up some watch the tach move. Some stick some dont move... taken a few somwhat apart to get them working... its fun.

03-29-2002, 08:19 PM	#1
Ironhorse Senior Member Join Date: Jul 2001 Location: Wellington, Ks Posts: 10,294	Tach Test? Can someone with a factory dash tach tell me how to test mine for operation before I put it in the new bezel and then in the truck? Have the tach, fact. GM printed circut, and the original harness. Heavy red wire with two clips or connectors, one has short pigtail connector and then a connector.(12 Volt power which hooks to 12 volt source unfused at fuse block), heavy brown wire (Hook to Coil Positive or Tach port on HEI) and then what? Does the tach use a ground? There is a threaded stud or attachment above the connections on the back of the tach. 'Preciate any help before I smoke test this thing. Got lucky couple years ago and found it in a truck at a 'yard for $15 for complete dash. Just been waiting until truck gets a complete re-build before I put it in. Thanks for any and all help. ------------------ 1971 Chevy 1/2T 4x4 LWB 350v-8 Wellington, Ks __________________ 1971 Chevy 1/2T 4x4 LWB 350 V-8 Was sm465-now 350TH/np205 Tilt, Tach, Towhooks Original Truck AM/FM Wellington, Ks

03-29-2002, 10:04 PM	#2
71Chev Senior Member Join Date: Dec 2000 Location: Indiana Posts: 3,074	The tach is grounded through the metal gauge housing. The case is grounded through the wire harness. To test it with out pluging in the dash harness, you have to hook up a ground wire to the case and the dash, and hook up the hot to the tach and to the distributer. ------------------ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear. Email: 67-72truckparts@nanosecond.com __________________ 71 Chevy CST Long Fleet 350/350/3.07 leaf rear.

03-29-2002, 11:08 PM	#3
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	I just hold the metal case of the cluster against the rad cradle... use the tach harness to supply the power and put the brown wire to the distributor. Rev it up some watch the tach move. Some stick some dont move... taken a few somwhat apart to get them working... its fun. __________________ Senior active founding member. 70 3/4 ton GMC Suburban 4x4 250/4 spd. 71 1/2 ton Suburban Chevy 4x4, 350/350 72 Chev 1 ton tow truck 402BB w/Holmes 440 wrecker on propane 2005 FLSTSCI Harley Springer 85 FXSB Harley Lowrider 72 Triumph 650 Bonneville 5spd "Poor people don't have hobbies" Quote from wife.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.