Home page
SPONSOR AD SPONSOR AD

Topic: Tach problem on my 76 w/4spd

in Forum: C3 Electrical


Tach problem on my 76 w/4spd

Posted: 8/28/05 8:43pm Message 1 of 5
Profile Pic
Lifetime MemberLifetime Member
Moderator
Send PM
Moses Lake, WA - USA
Joined: 4/16/2005
Posts: 2134
Vette(s): 1976 L48 4-spd, Mahogany Metalic exterior, Buckskin interior 350ci/350hp, 3rd owner, fiberglass spring, 255/50-16's Torq-Thrust II

It seems my tach starts acting eratic if it spends to much time at 3500 rpm. If I run at 75 mph for more than a 1/2 hour it will drop down and bounce around 2000 to 2500 rpm. If I get off the freeway and drop my speed down to 60 mph the tach will work fine. Do I have a filter problem?

Thanks




SPONSOR AD:: (Our Sponsors help support C3VR)

Tach problem on my 76 w/4spd

Posted: 8/29/05 7:21pm Message 2 of 5
Profile Pic
Lifetime MemberLifetime Member
Moderator
Send PM
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Well........I'm not sure if a '76 has a tach filter or not. If you have a wiring diagram, it should show one.
The problem could be the tach itself(gauge). Could be a little gummy, or sumpthin.
It could be the circuit board(ribbon), on the rear of the tach/speedo panel, or the connection thereof.
It could also be a problem with the ign. module, or coil connection.
I think I would start checking the connection at the dist. cap first, and make sure it is good & tight, with no corrosion, or moisture. Then you might need to pull the dash pad down & check the connections on it.

Hopefully, someone else here will have more info on this particular problem. Adams' Apple38593.8071527778


Joel Adams
C3VR Lifetime Member #56    

My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Tach problem on my 76 w/4spd

Posted: 8/29/05 8:42pm Message 3 of 5
Profile Pic
Lifetime MemberLifetime Member
Moderator
Send PM
Moses Lake, WA - USA
Joined: 4/16/2005
Posts: 2134
Vette(s): 1976 L48 4-spd, Mahogany Metalic exterior, Buckskin interior 350ci/350hp, 3rd owner, fiberglass spring, 255/50-16's Torq-Thrust II

Thanks Adam,

There is a filter on the back of the intake manifold but I did not see it in my electrical schematic. It seems to act up only after spending 1/2 hour running at 3000 to 3500 rpm. I do want to go through and recheck the wires like you said. I realllly do not want to pull the dash. I did a complete interior rebuild last winter and getting the dash all back to gether was not fun. The problem did happen before the interior rebuild so I don't think that is it.

On a good note, my sunburn from the Skykomish show is gone




Tach problem on my 76 w/4spd

Posted: 8/29/05 9:03pm Message 4 of 5
Profile Pic
Lifetime MemberLifetime Member
Moderator
Send PM
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
If it does indeed have the filter, just unplug it, and see if the problem goes away. I believe it is wired in parallel(?), so the tach should still work with the filter disconnected. If not, you could jumper around the filter.


Joel Adams
C3VR Lifetime Member #56    

My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Tach problem on my 76 w/4spd

Posted: 8/30/05 10:01am Message 5 of 5
Profile Pic
Lifetime MemberLifetime Member
Send PM
SHELBYVILLE, TN - USA
Joined: 7/5/2002
Posts: 3942
Vette(s): 1976 L48 auto

1978 L82 4speed

1994 LT1 6speed
 the 76 has a filter


StingrayJim
NCM Lifetime Member #1936

Stingray's '76���������������������������� StingrayJr's '78���������������������������Lil Red '94

(click each one to see a bigger version)

in Forum: C3 Electrical


SPONSOR AD: (Our Sponsors help support C3VR)