Factory Tach Install

[Gennoy]

Hey All,

I rebuilt my gauge cluster installing a factory tach. I put the gauge cluster back into the truck and plugged in the tach to my HEI and tried to start my truck. Unfortunately I get no spark with the factory tach plugged in. Once I unplug the factory tach from the HEI the truck fires up just fine. I plugged in an existing Sunpro tach I had into the HEI and had no problems. So it seems the problem is with the new factory tach.

The rest of my gauges all work fine with the exception of the "Battery" gauge where the needle just sits in the center. I know my truck is charging correctly because I get ~14 volts at the battery when the truck is on. But it seems the needle doesn't move. Is that right?

Unfortunately I am not the one who took my truck apart (I bought it in pieces). So I am slowly trying to learn how to put it back together. The only things running to the cluster are the gauge harness plug, the oil pressure line and the tach harness. Is there something that I am missing? Or is it just a bad tach?

Thanks in advance for all the help.

[72MARIO]

My battery gauge does not seem to move either. I have a new battery and alt. I have not seen one of theses gauges move very far mabye 1/16 " if ever. I would not worry about it.

[Gennoy]

Thanks, I was just hoping it was something simple like a ground not hooked up or something. I was thinking that the battery gauge may be an indication to the problem with the tach.

Frustrated seeing this beautiful new gauge cluster and having the tach not work.

[JimKshortstep4x4]

Make sure that the Tach housing is getting a good ground from the gauge housing and that gauge housing is well grounded.

On the ammeter, make sure both fuses are good, (one on each side of the radiator attached to the harness inside of small football looking rubber fuse holders).

Jim

[53burb]

As for the amp gauge, there are two fuses on each side of the engine bay, one by the battery and one one on the drivers' side. Those are usually burnt out. I don't have a factory tach, but IIRC, somebody else had this same problem, and I believe some of the other members said the tach is not grounded correctly. They will probably respond later.

[Gennoy]

How is the gauge housing grounded to the car? Is it through the harness, or is should there be a seperate wire grounding it to the chasis?

Unfortunately I live 107 miles away from my truck so I won't get to play around with it until this weekend. I was just hoping to get some ideas of what the problem may be before I get there this weekend.

Thanks

[JimKshortstep4x4]

Make sure the ground straps are in place from the engine to the firewall.

The gauge housing can be grounded to the metal part of the dash with a short length of black wire, (black is the standard color for ground wires). Using terminals on the wire fasten one end to the housing with one of the 1/4" headed fasteners.The other end is screwed to the metal part of the dash.

Jim

[Longhorn Man]

There should be a clip on ground strap from the inst panel to the dash....but it is normally missing.
The inst panel should ground OK without it, however, adding a ground is a good idea.

However, i don't think that's your problem. Normally, if there is a ground problem, the fuel guage will act stupid, esp when you turn on the headlights or a turn signal.

The ammeter is probably the fuses like mentioned. With the key on, engine off, turn on your headlights with the hight beams on, the needle should make obviouse movement to the left. If it doesn't move at all, then move on to the fuses.

Your tach is acting like it is wired wrong internally, or on your connections. One terminal is 12 volt input, the other is for the tach wire. It grounds through the frame of the inst panel. if you were to take that wire from the tach terminal on the dist, and ground it when the engine is running, the engine would shut off instantly. It sounds to me like that is what's happening here. Double check your 2 connections, the 12 volt in, should be on a keyed source on the fuse box. The ignition switch unfused is where you'd want to go with the power lead.

[Gennoy]

The kit I received came with a v-shaped plug for the back. I assumed it was wired correctly with the brown wire going to the HEI and the red wire going to the keyed source on the fuse box, but I did not look on the back of the gauge itself to see if that is correct. I will double check to make sure it is wired correctly. I will also put a ground wire from the cluster to the chassis to ensure it is grounded properly. There is a ground strap going from the engine to the firewall.

Thanks for all the help. What would I do without this message board?

[Gennoy]

Well, I thought I should give an update now that I figure out the problem. It is always the simplest thing. Thank you Longhorn Man for posting that picture of the back of the tach. I noticed on your picture that the tabs were pointed up and on mine they were pointed down. Which meant I had the wires backwards. After I rotated the tabs to look like yours I put on the V-connector and the truck fired right up. I guess I should have spent a little more time looking at the back of the gauge before I installed it. Owell, you live and you learn.

I also fixed the "Battery" gauge by replacing the two fuses as you guys suggested.

Thanks for everything.

[ChevyDude]

I just had this INDENTICAL problem!!! Rotated the clips on the back of the tach and...it fixed everything! Gots a tach now!!!

Did a search on the board...found this thread...and the answer!!!

[Longhorn Man]

Wow, I can put the name of a thread in the search, and come up with a bunch of crap totally unrelated, you do it, and it gets you a 2 year old post on the exact subject.

[BACKYARD88]

Originally Posted by Longhorn Man

Wow, I can put the name of a thread in the search, and come up with a bunch of crap totally unrelated, you do it, and it gets you a 2 year old post on the exact subject.

Wurd

[ChevyDude]

I think I searched "brown tach wire" and found this Andy. Funny thing is ...it was exactly to the T what was wrong with my tach.

[WorkinLonghorn]

Gennoy said;

So it seems the problem is with the new factory tach.

What I want to know is where do you find "new factory tachs" ? Unless he meant; "new cheap Korean-made tachs that are designed to look like factory ones". He hasn't posted in over a year so I quess I won't find out.