Tachometer Hookup Help - New Cluster!

[1972BlueC20]

Originally Posted by ray_mcavoy

Yes, the dark blue (oil light) and brown (generator light) wires are no longer used with the gauge cluster so you can save those terminals and re-use them for the #1 & #12 ammeter wires.

When it comes to re-using the terminals, I have in the past tried prying open the crimps and re-crimping them onto new wires but that is rather difficult to do without damaging the terminals. A better approach would be to simply leave a couple inches or so of wire attached to the terminals when you cut them off the dark blue & brown wires. That should give you enough length to splice them to the new wires.

Also be aware that the other end of the brown wire will still be connected to the alternator / voltage regulator. So insulate the cut end with some electrical tape or heat shrink tubing so it can't touch anything under the dash and create a short circuit.

Pewww....I'm so happy to hear this. This is exactly what I did. I took a chance and did this while waiting for a response from someone lol. Thx so much for all your help!!

Only thing left to do is to remove my old oil sending unit, and install the copper oil line in its place. Then hook it up on the gauge side as well.

I replaced my old dash pad while I was in there what a PITA !! Thankfully someone had left off the middle bolts near the radio. It was an original pad. A small quality control paper fell out dated 1971 when I pulled the old pad off.

Should have everything buttoned up today. Really hoping everything works as it should.

Also noticed recently a burning wire smell in the engine compartment before I started this cluster conversion. The fuse able link near the battery seems to be eminating this smell. What does this mean? I don't have any special non factory accessories. Just a custom auto sound head unit but not hooked to an amp. Recently replaced my alternator with the same one that had been in there for years.

What happens if my fuse able link goes out???

[ray_mcavoy]

Originally Posted by 1972BlueC20

Pewww....I'm so happy to hear this. This is exactly what I did. I took a chance and did this while waiting for a response from someone lol. Thx so much for all your help!!

You're welcome!

Originally Posted by 1972BlueC20

Also noticed recently a burning wire smell in the engine compartment before I started this cluster conversion. The fuse able link near the battery seems to be eminating this smell. What does this mean? I don't have any special non factory accessories. Just a custom auto sound head unit but not hooked to an amp. Recently replaced my alternator with the same one that had been in there for years.

That fusible link near the battery protects the main feed wire from burning up in the event of a short circuit or major overload. The fact that it's getting hot enough to give off a burning wire smell could be an indication of an overloaded main feed wire. But that's not very likely given that a Custom Autosound head unit is the only non-factory accessory in your truck.

A more likely cause would be a weak or corroded connection that is adding extra resistance to the circuit and causing the wire to heat up. So I'd recommend checking the junction block where the fusible link attaches to make sure it's free of corrosion, the ring terminal on the fusible link is in good condition and still crimped securely, and that the junction block nut is tight. The other end of the fusible link (where it attaches to the main feed wire) is usually pretty well insulated/sealed at the factory, but could still be subject to corrosion (especially since it is near the battery). Unfortunately, you'd have to cut away the factory plastic insulation cylinder to inspect that end. And it's possible that the fusible link wire itself has some internal corrosion that can't be seen due to it's insulation. If that is the case, you'd have to replace the fusible link. Use one that is the same size and close to the same length as the original.

Originally Posted by 1972BlueC20

What happens if my fuse able link goes out???

If it burns out, you will lose all battery power to the truck. If the engine happens to be running at the time, it will likely stay running off the alternator (provided the fusible link didn't blow due to a short circuit in the main feed wire). But if it's not running, you won't be able to start the engine if that fusible link is blown.

Also, with the addition of the gauge cluster, the main feed wire becomes a shunt for the ammeter (battery gauge). A blown fusible link leaves the shunt open circuit which has the potential to pass a damaging amount of current through the meter movement and it's wiring (the wires you are adding to the #1 & #12 spots). That is one of the reasons it is important to have the 4 amp inline fuses in those wires. They'll blow before enough current flows to damage the meter or wiring.

[1972BlueC20]

Originally Posted by ray_mcavoy

You're welcome!



That fusible link near the battery protects the main feed wire from burning up in the event of a short circuit or major overload. The fact that it's getting hot enough to give off a burning wire smell could be an indication of an overloaded main feed wire. But that's not very likely given that a Custom Autosound head unit is the only non-factory accessory in your truck.

A more likely cause would be a weak or corroded connection that is adding extra resistance to the circuit and causing the wire to heat up. So I'd recommend checking the junction block where the fusible link attaches to make sure it's free of corrosion, the ring terminal on the fusible link is in good condition and still crimped securely, and that the junction block nut is tight. The other end of the fusible link (where it attaches to the main feed wire) is usually pretty well insulated/sealed at the factory, but could still be subject to corrosion (especially since it is near the battery). Unfortunately, you'd have to cut away the factory plastic insulation cylinder to inspect that end. And it's possible that the fusible link wire itself has some internal corrosion that can't be seen due to it's insulation. If that is the case, you'd have to replace the fusible link. Use one that is the same size and close to the same length as the original.



If it burns out, you will lose all battery power to the truck. If the engine happens to be running at the time, it will likely stay running off the alternator (provided the fusible link didn't blow due to a short circuit in the main feed wire). But if it's not running, you won't be able to start the engine if that fusible link is blown.

Also, with the addition of the gauge cluster, the main feed wire becomes a shunt for the ammeter (battery gauge). A blown fusible link leaves the shunt open circuit which has the potential to pass a damaging amount of current through the meter movement and it's wiring (the wires you are adding to the #1 & #12 spots). That is one of the reasons it is important to have the 4 amp inline fuses in those wires. They'll blow before enough current flows to damage the meter or wiring.

Thx so much for all your help!

Got everything finished today and everything seems to be working fine so far.

This was one of the hardest most stressful projects I've done so far to my truck. But I have a sense of accomplishment now and my cluster looks great. Will be driving it at night this evening. Hoping all the cluster lights look good.

A few things I'm not sure about since I've never had gauges before.

The oil pressure is closer to the H (high) all the time. I have a crate engine. 330 HP - 350 with vortec heads. Is this normal for the pressure to be on the high side?

Also the battery gauge reads closer to the C rather than in the middle. Battery and alternator are both new. Is that normal ?

Tach acted funny (dropping off or jumping) a few times but then stopped. Now it seems to be acting normal. I installed a tach filter.

When I do anything electrical such as turning on the headlights to tach needle jumps a tiny bit. Normal ?

Again, thanks so much for all your help. I couldn't have done this without you, vettevet and TBONE.

Love this site!!!

[1972BlueC20]

Oh and my junction block post and nut are very corroded. I have a new one ordered and on the way. Hopefully if corrosion is the problem that will take care of it.