Thread: tach problem

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I have a problem with my tach, when I have the car running and turn on the parking lights the needle drops and when I turn on the headlights it goes to zero.

I've checked all the wiring and everything seems to be hooked up in the right order. I also hooked up another power source and nothing changes, even when the dash light for the tach was unhooked and the headlights turned on the needle still drops. The tach wire is hooked to the MSD ignition box like it should be (at least thats what the tech told me).

Any of you guys have a clue as to what's causing this problem.

Rocky

The gauges are Dolphin, and I do have the wiring diagram which all looks right.

As for a diode or capacitor it it doesn't say anything about it.

Charging system is fine.

And the wire for the light is correct.

I was looking at a wiring diagram and it mentioned that with an MSD ignition that you need a tach filter, but the tech at MSD said he didn't think that was the problem nor was it needed.

Rocky

I'll check that when I get back (the ground) because thats just how it's acting. I'll let you know how I make out.

Thanks, Rocky

OK, just got back from a cruise in.
The msd unit is a 6AL , the distributor is a msd pro billet small diameter street ford, and the coil is msd blaster.
I have the tach hooked to the tach output on the msd unit.

Denny, also noticed that when I turned my heater on the tach started to drop. The power is definately being pulled away from the tach, the good news is that the car runs great.

I did notice today that this battery that I have in the car seems like its lacking power, when the cars running if you have lights and the heater on the power windows go up really slow. The car is charging.
Could the battery being weak be causing this problem?????

Rocky

Yeah , knowing what kind of car it is may help . It's in my street rod a 32 coupe.

The car starts fine, and the lights are bright (unlike myself) and the volt gauge shows that its charging 12 to 14 volts.

I'm thinking your right about that ground problem. The guy I had wire this car screwed up more than enough, I've fixed more than just this one wiring problem.

Rocky

Bad grounds are the source of many electrical problems. If your '32 is glass it complicates the grounding issue even more, as you won't have the metal body to act as some of your ground circuit.

I would start right at the battery. Your ground probably goes to your engine block? If so, you also need something like a braided ground strap going from the engine or transmission to the frame. Then you need some kind of a central ground block under the dash (or somewhere) where all of your accessories electrically ground back to. This central connection has to be connected back to the battery negative post for the best connection.

The big clue here is when you say your power windows will also slow down. Your circuits are searching for a good ground. Make sure every connection is clean and bright and goes to a bare spot to ground to. Painted surfaces are not a good ground connection.

Don

I do believe your right , and tomorrow I'm going to run a new ground and hopefully that will solve the problem. I'll keep you guys posted.

Thanks, Rocky

If you saw my post 2-3 wks ago you will remember - I called MSD & Classic (my gauges) seems there are compatablity problems w/ MSD & after market tachs , The filter on mine made it even worse. 31 5w

Have you solved the problem yet???

No , I unhooked tach sending wire got rid of occasional miss , they told me to remove filter and hook tach directly to - (point) side of coil. I have not yet done that as car is running so good i am afraid to screw with things right now, I know this sounds " anti- hotrod spirt" but I just want to enjoy the car running @ its best before "Testing a new theory" 31 5w

Well I tried different power supplies and grounds, unhooked the dash light in the tach and still the same deal.
I saw somewhere that if you hook to the coil without the filter or adapter that it will fry the tach, don't really know.
As for the anti-hotrod spirit,Same Here. I've decided not to worry about the tach it works when the lights are off and thats good enough for me. I'd rather enjoy the car than worry about something so stupid.
If you figure it out let me know and then I'll fix mine to.

Rocky