I recently had issues with brake lights/taillights/ dash lights. I have all that sorted now, and now I have issues with a new problem.

I have a 5 inch tach and 3 aftermarket gauges installed in my chevelle. They come on with dash lights. All the lights work properly except the tach light. In addition to that, my shift light will not come on when you crank the car. The shift light is suppose to briefly light when you turn the ignition to on. Can't set the shift point because the dial will not turn the pointer (maybe a tach issue). When I turn my headlight switch on it kills the tach. I have the gauges plugged into the lamp terminal and ign. terminal on the fuse box for power. It's driving me crazy trying to figure this thing out!

I dont have a voltmeter, but do have a test light. I have a light at all spots on the fuse box when the car is running. I beginning to thing that I might not have 12 volts at each spot. I have had the clean the fuse clips several times over the past few months and have not driven the car over 1000 miles.

Any help will be appreciated.

A guess is that maybe the tach wires are crossed somehow. Two of your problems center around the tach. 1, The tach light isn't coming on and 2, The headlight switch kills the tach. Maybe the tach input is reversed with another wire.

Can you get the tach light to light up hooking it to a known hot? Does it have a seperate bulb or is it an LED? I know if i start having troubles i just start to go back to the basics, do you have good connections? the connections that i get with my autometer tach/guages etc. IMO are junk, i always cut them off and soldier on my own connections. Haven't had a problem with my wiring but autometer's i have had bad connections. The connection was always tight but the metal used seemed quite cheap.

Also did you drop the guage of a wire when hooking up? sometimes that can make things not work. Good luck!

John and Gumball

I dont have any wires crossed. No LED to my knowledge. Shift light has its on blub. The blub that lights the tach will come on when you press the display button (red button).

Do have the tach connected to a rev limiter, but don't believe this would cause any problem.

I'll try switching the wires at the fuse box.

Gumball

I attached the gauge lights wire to a known hot and the tachs light did come on with the other gauge lights. This makes me wonder if enough juice is coming from the lamps connection. I do get a test light at each side of the fuse box though.

This however does not explain why when I pull the headlight switch out the killing of the tach.

Since the lights worked on another circuit, you may have to much resistance in the lamps circuit somewhere. What kind of test meter are you using? As a test, hook gauge and tach lamps back up, test for volts with the lamps on.

Gumball
This however does not explain why when I pull the headlight switch out the killing of the tach.
You may be getting to much voltage drop because of connections or wiring and the tach shuts off to protect itself.

I'm just using a test light. I have a voltmeter coming as I write this. I will post my findings.

Gumball



This however does not explain why when I pull the headlight switch out the killing of the tach.
Where are you getting power for the tach? As a test run a wire to the battery with a inline fuse to the tachs power wire, start car and turn on headlights. If the tach works you have a power problem.

These are my connections:

1. Green=Tach spot on HEI
2. Red=IGN spot on fuse box
3. White=Lamps spot on fuse box
4. Black=Ground to dashboard

Still do the test, run a new wire to the battery with a inline fuse to the tachs power wire, (red one) Post back with results.

Undee70ss

I ran a wire to the + battery. ALL (3 gauge lights and tach light) lights came on when car was cranked. When I cranked the car the tach worked. When I pushed the display button on the tach the shift light came on like it is suppose to and I was also able to the shift-set to program the shift point.

I believe my problem is somewhere in the fuse box. The bottom fuse is for the taillights and brake lights I believe. That runs up to the headlight switch and then back to the lamps fuse. One of the two fuse clips is bad and needs a fuseholder I believe.

My understanding is to get a GOOD light all you should have to do is touch the metal. On those clips I have mentioned you have to move the clips a little with test light to get it light sometimes.

Undee70ss



I believe my problem is somewhere in the fuse box. The bottom fuse is for the taillights and brake lights I believe. That runs up to the headlight switch and then back to the lamps fuse. One of the two fuse clips is bad and needs a fuseholder I believe.


Yr of car??? Sometimes needed info. A bad fuseholder might explain the lamps problem but not why the tach wasn't working with the headlights on since its on the IGN circuit. Are there any other electrical issues ( dim lights ect..) ? How many other add ons ( stereos, amps ect...) ? In addition to the bad fuseholder, you may have a bad connection supplying the whole fusebox. Other things to check would be the firewall bulkhead connection, horn relay buss bar, and the junction block on the rad core support. You could also do voltage tests at the key check points ( back of alternator, battery and horn relay buss bar) and compare them to readings at the fuse box. You have to do this with everything on ( headlights, radio ect...) to determine where the bad connection might be.

Car is a 67 chevelle coupe. I checked all the spots you mentioned. Bulkhead connection, horn relay, and junction block are all good and solid. I got readings of 11.5 to 12.01 on the battery, alternator, and horn relay. I checked all the fuse clips and they range between 4 and 11. Some are more steady than others.

When back and checked the fuse box again for specific voltage at each clip.

10.3-11.3 Wiper fuse 10.9-11.3
10.9-11.3 Heater fuse 10.8-11.1
10.97 Radio 10.7 ACC: 10.7
9.53 Ins/Lamps 9.46-9.8 Lamp spot: 9.3
10.7 Bk-up/Gauges 10.6-10.9 Ign: 10.69
10.7 Lighter/Hazzard 10.7 Batt: 10.68
10.6-10.7 Stop/Taillights 9.6

These were with the car running, the radio on (modern radio in blove box), headlights on.

What is the voltage reading at the battery, alternator, and horn relay with the car running, as we need something to compare it to under the same conditions ( car running, the radio on (modern radio in blove box), headlights on.) Post back

Anywhere from 11.5 to 12.01.

Anywhere from 11.5 to 12.01.
If thats all you are getting at the battery, alternator, and horn relay with the car running then the alternator is outputting anything. You are just running off the battery. If you drove the car far enough the battery would just go dead. You should have 14-14.5 volts at the battery with the car running to charge the battery and run the rest of the car. Do you know if your alternator is externally (which is original) or internally regulated? Do a search on my user name, a general search or start a new thread on the alternator. Back to your original questions in this thread, I would fix the charging problem first as this would put the voltage levels where they are supposed to be with the car running. The voltage drop doesn't "look" bad except the lamps,

9.53 Ins/Lamps 9.46-9.8 Lamp spot: 9.3
:sad:
which gets its power from the headlight switch. Voltage is supposed to be a little lower with the headlights on but you are getting 2+ voltage drop.It could be just the fuseholders. One thing you can check is to make sure all of the fuses are tight in the fuseholders. They should wrap the fuse tightly. You should be able to poke at them and they should not move. What can happen is after removing fuses and cleaning the clips, the clips may be bent and are not graping the fuse tightly. You may need to squeeze them a little with needle nose pliers before inserting the fuse. This will insure a good connection. Now the original question of why the headlights were killing the tach, with no output from the alternator and lower voltage levels from just running off the battery the tach may just been shutting off to protect itself. Without actually being there see how everything is wired, it would be hard to give further advice. You may in the future want to consider adding a fuse box just for your add ons such as a painless 3 circuit box, Summits part# PRF-70103. The factory wiring wasn't made to handle many add ons and a added fuse box will take the load off the factory wiring. Hope all of this helps, if you are still having trouble email me your phone#

The alternator is a internal one. It is practical brand new, installed it with new motor, less than 800 miles on it.

I have noticed that periodically when I crank the car for the first time in the morning that I get a 2 second whine from under the hood. Someone sugguested that it might be a bearing going bad in the alternator. Also when I fire it up in the morning I get a high pitch sound (hard to describe, whine sound, not unbearable) that last until the car reaches operating temperature. Could be associated with the alternator.

I get a tester and check it.

I look at my clips and check them with a pair of needle nose. The lamps fuseclips move around more in the box than any other clip.

Thanks for you help. I'll email you my # number.