68/69 Rally gauge swap from standard gauges

[69customS]

Ok, so if your like me you like the rally gauges much better than the idiot lights. When I got my 69 custom S I had the rally gauges installed already but NONE of them worked...including the Tach. So I started inspecting the wiring and the gauges themselves. I did a lot of reading and talked to a bunch of people. I finally figured out quite a lot of information and now have gauges that work!

2 types of gauges (Standard & Rally)

Lets start with the easy one... The TACH. If you look at the back of your tach and there is only 1 wire... you most likely have a POINTS only tach. If you are trying to use this on an electronic ignition... it will NOT work. You will have to get it updated. There are several option out there and I am not here to tell you who to use. It will most likely cost around $300 to get it upgraded. They will have to swap out the circuit board inside and add a post on the back for 12v power. Or you can get a different tach with the  2 prongs on the back. I chose to get a repop... and it works great. 

1 pin (points only tach) 2 pin (electric ignition)

Now the much harder one... the main cluster. If your like me and you plugged everything in and nothing worked... dont fret. It can work. The wiring pinout on the plug that goes into the back of the cluster is different from the standard gauges to the rally gauges. Its only 2 of the wires... but with those two switched, your fuel gauge will not work. Swap the wires and look out.... IT WORKS!!!!!! (ill post pics for you to see what Im talking about.) The OIL gauge and TEMP gauges have a little bit more to do. Most likely you will have the sensors that go with the standard gauges (just an idiot light) so those sensors will not be sending the correct signal to the actual gauges on the rally gauges. So you will need to swap out the oil pressure switch and the water temp switch. Dont worry... you can get both ACDELCO from rockauto for about $35. Swap out the sensors and all should be good now... as long as your gauges are working correctly. If your gauges are not working at this point I would have them inspected or follow the wires and make sure they are in the correct place. 

***UPDATE*** I just got an email from PETE about the temp switch. He said that some of the newer temp switches will give you an incorrect measurement. After installing yours, you might want to check the temp with a thermometer in the actual radiator to verify if the gauge is correct. He said some of them can be 25-30 degrees off.  

Cluster PLUG

Standard gauge circuit 

Rally gauge circuit

Standard gauge pinout

Rally gauge pinout

Pin callout for connector

I have tried my best to be clear on how to swap this over but if you have any questions... please shoot me a message. 

Edited May 7, 2019 by 69customS

[Ant]

Thanks for the write up, if anyone needs to have gauges fixed the best guy out there is Peter Siero of Precision Pontiac. We've had him do a bunch of sets over the last 20 years. He did my main cluster in my 68 and several sets for 65s for us. I had bought an aftermarket set for the 68 and since you have to use your speedo they looked  like junk the colors didn't match at all. So I dug through my old files and found Peter's number and he did an original set for me and they came out great!!

Ant

[69customS]

haha.... too funny. I actually spoke with Pete on the phone and he is the one that got me thinking about the setup of the gauges. He told me about the wiring being different... which lead me to finding the correct wiring after following the circuit on each of the printed boards. Great dude... and full of knowledge. He even went into detail about how the gauge needles are able to move because of the glycerin that acts as a lubricant and how the gauges almost always work unless that drys out. I thought my gauges were broken... but after talking to him I did more research and found which wires were in the wrong spots... and which sensors to swap. Without talking to him i'd still be in the mindset that the gauges themselves were broken.