For those like me who have simple indicator light gauge clusters, and want a tach & oil pressure gauge





Understand that your wiring harness is different than that from a truck with full gauges. Therefore it has a different connector. Also, your instrument cluster is physically different, to accomodate the RPM gauge.



1. you need to bring from the junkyard a instrument cluster with full gauges
+ you must also bring the connector from the harness WITH wires still sticking out of it (AKA cut the harness 4 inches from the instrument cluster connector and bring the connector with wires sticking out home
Note: you need to make sure the truck is the same year as yours, this is important because you will need to match wire colors between this connector and the one in your truck when you repin the connector
+ you will need to bring the connector under the hood for the tach. It is a fairly large brown connector with either 1 (for 6cyl) or 2 (for 8cyl) wires going in. This connector is located near the duraspark box, on LH side inner fender.


2. you will need to install the battery indicator light from your cluster in the gauges cluster
- this roughly involves carefully cutting out the white plastic light blocking shield from your old cluster, glueing it into your new gauges cluster, etc (this part took me 2 hours, its straightforward)



3. cut out a hole in the printed circuit for the BAT light to pop into, and also install the large resistor in the proper place (SIMPLY, you must verify that the BAT indicator light is hooked up exactly as it is on your original cluster)



4. You will need install the new larger instrument cluster connector in your truck. This means you will need to repin connectors. Wire colors remain the same EXCEPT for 4 wires -> Your indicator lights connector has 2 less wires than the one you brought from the junkyard, and 2 other wires that will NOT match colors. The rest of the wires are the same color, in both harnesses.
Looking at your new connector with wires still attached, and your new gauge cluster circuitboard, you will figure out which 2 wires are for the RPM gauge, and which 2 are for the BATTERY gauge.

The 2 that you are missing, those go to the TACH. You will need to run these wires from the connector thru your firewall and into the connector on the LH inner fender well near the duraspark box

If you have a 6cylinder, you will NOT be needing the wire that goes to the "8" terminal on the back of the tach. If you take the tach gauge out from the cluster, you will see markings near each terminal. I believe they are B C G and 8. terminal 8 is ONLY used if you have a 8 cylinder truck, do not even bother running the wire if you have a 6 cylinder.

The other 2 that are the wrong color, are for the BAT gauge. You are not installing a bat gauge, so you will just substitute your wires and essentially MAKE SURE THE BAT LIGHT IS HOOKED UP SAME AS IT WAS.

If you repin the connector carefully by making sure the wire colors go into the proper places in the new connector, you will not fck anything up.



5. Solder the wire(s) you ran through the firewall to the pigtails on the brown connector that goes in the engine bay, on the LH inner fender. Then, connect to the secondary wiring harness @ engine. (There should be an unused connector there, just plug into it. Mine was like this - I'm hoping all the trucks are)


6. You will need to install a oil pressure sending unit on your engine, instead of your oil light unit which you have now.


I have a 1980 6 cyl 300 truck. I only had to run 1 wire from the connector thru the firewall, everything else remained the same.

Sorry for the scatter brained tutorial, its dec 31 and you have no idea how much I didnt feel like writing this haha. I have this fully functioning in my truck, it works wonderful and it looks custom.

Its a lot of reading, its NOT A LOT OF WORK, its a weekend job at most and you get to keep your wiring harness.

Enjoy, happy newyear

 

Your ideal of putting the batt warning light in place of the almost useless amp gauge is a good one! As my 84 F250 already has full gauge and tach, but not functional amp gauge, I may do this to my cluster.

 

Excellent post. Thank you. Can't wit to try this on my '81 F-100 4.9. It has the plain ole idiot lights and just wiring in a factory tach won't do because on mine the tach goes right where the harness plugs in.

I made a PDF of this thread to save.

 

thank u for posting......

that answers my dilemma about he charging system: light or gauge