Hoping someone can help. I've been restoring my '68 400HO and I working out some wiring bugs. I have installed my hood tack but it only operates when the highlight switch is on. I checked the diagram and it shows that you are supposed to plug it in to the "LPS" (lamps) circuit. Should I switch it to an accessory circuit on the block?
Kevin you are suppose to install the gray wire that goes to the lamp in the fuse panel 12v source. Look at the tach plug you will have 5 wires 1 brown for lights,1 black to light, 1 purple to tach, 1 black to the tach, 1 black to tach. is this correct? I'll post the instructions for you next post. they don't talk about the light wire in it and they refer to the tach plug, not the harness plug.
INSTALLATION INSTRUCTIONS FOR HOOD MOUNTED TACHS 67 GTO-Firebird Please read all of the instructions prior to beginning installation. Failure to follow the instructions may void your warranty. Your hood tach is a quality product that should give many years of service with a little care during installation. Template: Use the template to cut the holes in the hood. The Template has instructions for a 67 GTO-Firebird. Installation on other makes, models, and/or years may require placement in a slightly different position in order to clear the under hood braces. If in doubt, measure before you cut. Mounting: this is very important. Your hood tach is carefully sealed to be water tight. When attaching the hood tach to the hood, be careful NOT to over tighten the nut on the studs. Over tightening may cause the base of the tach to warp and destroy the water tight seal. Remember, it is not necessary to “torque it down”. Electronic hook up: The black wire with the attached metal connector should be securely attached to the firewall or other source of a good ground. The second black wire (Without the metal connector end) is connected to an ignition controlled 12 volt power source, such as the black or yellow wire leading to the windshield wiper or washer moters. This connection is made with the included blue plastic connector. The brown wire is connected to the negative terminal of the ignition coil. The plastic male connector of the wiring harness fits into the female portion of the plug, which is part of the tach unit. Note: The case of your tach is painted with a dark lacquer primer. You may want to mask it off with masking tape prior to painting to match your car. This will avoid the problem of scraping paint off the glass face. Enjoy Your Tach! ! ! ! IMPORTANT ! ! ! ALWAYS TEST YOUR TACH BEFORE YOU INSTALL IT,, PAINT IT,, ALTER IT,, OR CUT THE HOLE IN YOUR HOOD.. Tachs that have been installed, painted, or altered in any way cannot be returned for replacement or refund. Some cars may require special adapters or may not work with this tach. This tach was not designed to work with OHC-6. So be sure to test all connections first. This tach uses new electrical parts. We do NOT recommend using old wiring as it may damage to your tach. All tachs are properly calibrated before they are sealed. On occasion we get a tach that the needle sticks. This is usually because a bit of silicone is in the way. We suggest the True Mechanic’s Method to fix it…VERY GENTLY “bump” the top of the tach with the side of your fist to free the needle. Be extremely careful when doing this for three reasons: the face of the tach is real glass, you don’t want to break the silicone seal, and you don’t want to offset the calibration. If the mechanic’s method doesn’t correct the issue, and you have already double checked your connections, contact us for help.
I can help with this one. My 69FB had the exact same issue for many years. It wasn't until I happened across an Inline tube article about a GTO that I found the answer.
There should be a hidden wire in your harness as at least there was in mine. As you can see in the picture it is behind the wire harness behind the parking brake.
Thanks for the tips guys. I gonna spend a little time this evening and try to figure it out using your info. I never really had to wire anything as mine was factory and I bought a new one that came with factory harness. I guess I need to investigate the harness a little more. I'll keep you posted. Thanks again.
did you say you bought a new repo tach.? If yes you will need to separate the brown light wire from the black wire that goes to the tach so the light will come on only with the headlights pulled and tach will work when the ignition is on. Or just install it on the Acc. 12v source but the light will be on all the time but the tach will work too.
Thanks. I did actually move it over to an accessory plug and it works fine. The light stays on, but that's ok. It probably helps with condensation, since I didnt hook up vacuum kit. I think the light was supposed to stay on before they came out with the vacuum line fix. Thanks for the help.
Thanks. I did actually move it over to an accessory plug and it works fine. The light stays on, but that's ok. It probably helps with condensation, since I didnt hook up vacuum kit. I think the light was supposed to stay on before they came out with the vacuum line fix. Thanks for the help.
The light/lights are supposed to be on at all times. Either way condensation (factory units) will still be a problem. My 69 factory tach died from condensation even with two strong bulbs in it.
I have heard of dimming the lamp, but then you'd need to wire it separately like I did mine. If that was the case They stay on all the time, then why would the factory service manual install the Tach lamp wire on the lamps terminal of the fuse box?