Topic: Is my Tach trying to tell me something?
in Forum: C3 Electrical
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I've noticed that when I put my foot on the brake (thus lighting up the brake lights) my tach will jump a little. Yesterday it was very overcast so I was driving with my running lights on. When I put my foot on the brake, the tach jumped even more. By the time I got home, it was dark so I had all the lights on and with my foot on the brake, the tach was really jumping a lot. So it seemed to bet getting worse as more lights were on.
Is this a tach problem or just indicating another problem? When my brake lights aren't on it appears to behave fine - regardless of what/how many lights I have on at the time.
Is this a tach problem or just indicating another problem? When my brake lights aren't on it appears to behave fine - regardless of what/how many lights I have on at the time.
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Castle Rock, CO - USA
Joined: 4/21/2002
Posts: 179
Vette(s): 1973 T-Top
1993 Coupe
Hello Eric,
Your tach is telling you that there is a ground problem. The brake lights are back feeding through the tach ground causing the jump. Many times you will see the turnsignal indicators light up with this condition.
I would check the grounds at the tail lights first, as I remember the car was re-painted recently. The body guys are notorious for not replacing ground wires or putting them to a fresh painted frame with no contact to metal. Have someone watch the lights as you apply the brakes. Look for a dim one. Check all the lights this way. The dim one/s are suspect. Use a jumper with alligator clips to try completing the ground.
Finally, if all else fails look for a loose ground under the dash. This is difficult even for the double jointed. Try this last. Although possible it is relatively unlikely.
Alex
Your tach is telling you that there is a ground problem. The brake lights are back feeding through the tach ground causing the jump. Many times you will see the turnsignal indicators light up with this condition.
I would check the grounds at the tail lights first, as I remember the car was re-painted recently. The body guys are notorious for not replacing ground wires or putting them to a fresh painted frame with no contact to metal. Have someone watch the lights as you apply the brakes. Look for a dim one. Check all the lights this way. The dim one/s are suspect. Use a jumper with alligator clips to try completing the ground.
Finally, if all else fails look for a loose ground under the dash. This is difficult even for the double jointed. Try this last. Although possible it is relatively unlikely.
Alex
It sounds like a ground issue to me too. Looking at the side pipes on your car got me to wondering.......
My car has a ground strap from the frame crossmember to the exhaust clamp beside the tranny, When you guys put the pipes on, are you supposed to ground to them? I've got 3 straps from the body to the frame, but only one to the exhaust.
My car has a ground strap from the frame crossmember to the exhaust clamp beside the tranny, When you guys put the pipes on, are you supposed to ground to them? I've got 3 straps from the body to the frame, but only one to the exhaust.
Lifetime MemberHot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
yes its trying to tell you...
"Welcome to the wonderful and exciting world of owning an old Corvette... Now fix me!!"
sorry I couldnt help it.
"Welcome to the wonderful and exciting world of owning an old Corvette... Now fix me!!"
sorry I couldnt help it.
in Forum: C3 Electrical
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