Aftermarket gauges back to factory gauges questions.

[Jayschevy]

When I got my truck the PO was using aftermarket volt, water and oil gauges instead of the factory gauges in the instrument cluster. I'm not sure if the old cluster worked or not but since buying the truck I bought another cluster but the water and volt gauges still do not work. My question is:
1. On my trucks factory volt gauge in my cluster can I just unhook the 2 wires connected on my aftermarket gauge and just hook them up to the two connection terminals on my factory gauge to get it to work?

2. Just hook up the fitting on my aftermarket oil pressure gauge to the factory oil pressure gauge to get it to work.

3. How do I get my factory water temperature gauge to work? My factory water temperature gauge only has electrical connections in the back. My aftermarket water temperature gauge has some type of probe going to it. So how do I remove this to get my factory gauge to work?

Any help would be appreciated.

[WIDESIDE72]

The oil pressure gauge is the easiest to return to stock as long as you have the original type line, just swap it like you said, but i dont think the aftermarket connecting line works with the original gauge. Brothers sells a line kit for around $20 or so if needed.

As for the temp and volt gauge, those are both electrical, not mechanical like the aftermarket temp gauge. For the temp gauge youll need to remove the aftermarket probe and replace with a new sender from your local parts store. The wiring for both original gaiges is part of your trucks engine wiring harness. The coolant temp wire is green. Look for it taped up somewhere on the driver side of the engine compartment. Hopefully the p.o. Took care in it not getting burned up on the manifold.

As for the volt gauge and how it ties in, it is part of the printed circuit and there are no additional connections.

Do a search on this site for a wiring diagram to get it straigt if needed.
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[VetteVet]

Yes the oil gauge should just be a swap since it has no wires only a pressure line.

If your wiring is intact and good you should just be able to plug the connector plug into the cluster gauge and every thing should work. We all know how this goes LOL. Make sure the cluster is grounded to the dash well and the cab has to be grounded too. Most likely the cab is grounded but the cluster may not be.

You probably had an aftermarket voltmeter but your cluster has a different animal . It is called a battery gauge or ammeter. The voltmeter uses positive and negative feeds but the ammeter only uses positive inputs and wiring a negative or ground to it will create a short and most likely burn up the gauge.

If you look at the cluster plug you should see a small set of black wires on the end. One of them will have a stripe on it. These are the feed wires for the ammeter and they are located on the pins 1 and 12 on the cluster plug. These are the two wires that go to the ammeter. If you have a multimeter you can check for 12 volts on each of these wires with the key on or off. One of the wires goes to a junction of the alternator and the regulator and a wire from the battery positive called a SHUNT, and the other goes to the junction of the battery fusible link and the other end of the SHUNT. This junction is nothing more than an insulated bolt mounted on the right fender well just to the right of the battery.

There are two small 4 amp fuses on each of these wires that protect the gauge from high current, and are the most probable cause for the ammeter not to work, IF the truck is stock. These fuses are hard to find and are usually located in the harness that goes over the radiator and down by the horn. They are contained in small rubber covers that look like footballs.

When the wiring is altered by a PO or somebody wants to convert alternators or install a One-wire alternator and they reroute the alternator output, they can defeat the purpose of the SHUNT which is there to allow the ammeter to read the voltage difference between the battery state of charge and the alternator output. These two diagrams will show what I have stated about how the ammeter works and the wiring to it.

Here is the picture of the stock wiring with the SHUNT and the fuses circled.



This shows how the alternator and the battery must be wired for the ammeter to work. Notice each of the ammeter wires goes to the opposite end of the SHUNT.



Here is the cluster plug for the gauges with the wiring shown. The ammeter wires are on the 1 and 12 pins. Notice also that the green temperature wire mentioned by Wideside is on pin 6 at the opposite end of the ammeter wires.




The temperature gauge wire and the sender can be found in the center of the second diagram where it runs from the sender in the engine block cylinder head, through the firewall connector to the gauge plug. If you ground this wire to the block the gauge will go to full hot and if you do not touch it to anything the gauge will not read or it will go to cold. If you get this reading then your sender is most likely the problem. Make sure the key is on. This is a grounding wire so touching it to the block will not cause a short.

Here is a better picture showing the temperature gauge wire.




You really need to make a signature and tell some details about your truck especially the year. I had to search your posts to find out it is a 71. It really keeps the guessing games down.

[SS Tim]

Might be a good idea to check your SPID for Z53 gauges or U16 tachometer as original equipment for a start.

[Jayschevy]

Yes it's a 71 basic truck. It only has speedo and fuel gauge no tach alone with the amp, volt and water gauges.
Looking at the wires under the hood it looks like I may have to get a new engine wiring harness if I want the factory gauges to work. The PO cut a lot of the factory wires.