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I am replacing the blank panel (where the clock would be) with a Tach. I found the gray wire for the Tach lighting, but I cannot find the Orange wire for power. Can I run a wire from the Accessory fuse to the tach?
Yes, use something with switched power such as the accessory fuse (or the IGN terminal). Don't use the clock constant power orange wire.
If you are going to use the tach/clock combo, then you will need to use the constant power wire to power the clock. If the harness was not molested, the orange wire should be there
The orange wire is full time 12V. It runs in the dash harness and powers the glove box light, clock, and other functions that need full time power. It also powers the dome light. If you are using an aftermarket tach, you do not want to use this as the power source. You want to tap into the gauge power circuit that is only hot in the RUN position.
Update:
1. I have lights on the tack
2. I used the Accy fuse to power the tiktok tach and the clock works
3. Tach: When I start the car the tach needle goes from 0 to pegged then back to 0, but after that it does not show any RPMs.
I have a MSD coil and the ttt manufacture recommended a resistor between the coil and the tach. there already is a resistor on the firewall where the Coil + hooks into. I have the tach wire (fused) connected into what I think is the negative of the resistor. Am I doing this correctly? Please see the diagram. I am so close...
OK, first off thank you for finally saying what you are working on: Tic Toc Tach and an HEI distributor. We really need to know what you have in order to give correct advice.
With that said, is this a real HEI or a points distributor with an electronic conversion? There is a significant difference. We need to know that before going further.
I purchased the car with the system in it but I believe this is real HEI system (Mallory Pro Master Coil PN: 29440), because when I removed the distributer cap and rotor, I did not see any points, but I could be wrong.
Good Morning,
I spoke to Holley (Mallory) and they stated my distributer is old fashion points style. I mentioned to him that with the Tach connected to the negative side of the resistor, I receive no reading. He stated that may be because the voltage at that resistor is too low. The TTT seller (The Parts Place) stated it is recommended to use a resistor as the new HEI coils run at 18 V.
Yeah, Rather than make us guess, why don't you post photos of exactly what you have. Pictures of the distributor (with cap on and off), coil, any add-on boxes, any resistors, and a good photo of the wiring. Whatever you have is not stock, so without detailed info on exactly what was done to your car, it's impossible to supply useful info. Right now it's the 1,000 monkeys with a 1,000 typewriters problem. You MIGHT get Shakespear, but chances are you won't.
First, you don't have anything "HEI". That box is the ignition coil, period. The distributor is a Mallory Unilite optically triggered electronic distributor. Whoever told you that was a "points distributor" is clueless. Run, don't walk away.
Here's how Mallory says it should be wired. Note that if your car has the original resistor wire feeding that ballast resistor, you have too much resistance and will have too low a voltage at the coil.
The tach feed should be connected to the NEGATIVE terminal on the coil. It should not be anywhere near the ballast resistor or the positive side of the coil. Of course, we don't know if your aftermarket tach is working correctly either. If you have a tach/dwell meter, connect it to the negative side of the coil and see if you get a reading with the engine running. If you do, there's nothing wrong with the ignition system.
Note this is the wiring for cars like Oldsmobiles that have a resistor wire built into the harness. There is no external resistor used. Who installed that system in the first place? Did they keep the original resistor wire or not?
Mission accomplished. Thank you for being so patient with me and your incredible knowledge on the ignition. I hope one day to be as knowledgeable to one day help someone out too.
