Hello all I wanted to share with you how to update your gauges in your car to work with the stock sending units and to make them work properly. I might get long winded but If You have questions please ask and I will do my best to answer them. As you can see in the photos below for the main dash pod I retained the standard idiot lights. I did not take photos on how I did this but will explain. Please not this is in an 85GT so I had to add the wiring to the center councel as mine had none there. THe best way to start is to take out the gauge pod fully and daisy chain the main wires that you will need like switched power, Illumination, and Ground.
Illumination tap into the green and there is a strip wire on it at the dimmer. Its the bottom wire. This will supply a controlled amount of light. You will need to daisy chain 5 splices or how many gauges you are putting in. for me it was 5 to the right and three to the left. Make the runs to they will reach each gauge and run the next to the next gauge and so on.
Ground Do the same as above you can chain it to Pin #11 witch is the ground behind the instrument cluster. This is on your 18 pin connector on the back of the cluster There are three connectors. The one on the right witch is 18 pins. The one on the left witch is 12 pins and the one on the bottom that plugs into the speedo.
Switched Power I tapped in but don't remember what pin.
Please note these are all electronic gauges.
Lets start with water, Fuel and volts.
For Water I chose Eqquis gauges for these three as the ohms numbers match up to what the gauge takes 1400 - 55 ohms 1400 is cold and 55 is hot. So you want to connect pin 11 from the small connector to the gauge and that is it.
Fuel is 0-90 ohms and the Eqquis gauge is a match to this as well. This will connect to pin 7 of the big connector on the right side. Splice into it and connect to your gauge and you are done.
Volts takes care of its self. you have the ground ILL and switched power there so you need no extra. you turn on the car and it tuns on.
Here are the main gauges installed with the idiot lights. what you do here is take the cluster apartall the way down to the the whit shell and circuit board on the back. take all the lights out but the ones in the middle for the idiot lights. you will need a hot glue gun and super glue to get the idiot lights to stay in the cluster. first you want to apply super glue to the see through pieces and line them up and glue them to the white stands they are on. Now the white stands will just fall out if you try to super glue them in so you will need to load it up with hot glue around the out side and when it drys then you have your idiot lights. now there is two layers that go in front of this to complete the cluster. there is a metal frame and a clear plastic overlay. Toss them to the side as they are no longer needed. and you will end up with the photo below. add some material to the inside if the front bezel and super glue it in to close off the empty wholes and end up with this.
Now for the speedo to work there is a little trick to it.you are going to splice into the yellow connector on the speedo harness that is at the bottom of the dash. This is the third plug. Now our speedos work on pulses per second. For our cars it is 4000 pulses per mile. Now the strange thing is that our speedos are digital while the obd2 gauges are analog. so there needs to be a buffer to make it work. Most gauges are digital at this time so its kind of backwards for our car. There is a real easy solution for this. On the 85gt speedo circuit board there is a buffer on it already to convert it. So to make this work tap into the yellow and put that on your in on the speedo. here comes the easy / hard part. Get your old speedo and take the 4 bolts off the back and remove the speedo from the circuit board. get yourself some electrical tape and wrap up the board so it will not short out and then plug it back into the harness and hide it in your dash. This will create the buffer that is needed and now your speedo will now work. Tuck the board into your dash and that is set. Follow you manufactures recommendation to get your pulses correct. I went with autometer pro comp gauges for this.
For the tach it runs on voltage not ohms. I again chose an autometer pro comp gauge for this. The car puts out 1-6 volts. 1 should be idol and 6 is read line.So you want to splice into Pin 18 on the large connector and thats it. Now most tachs that I have used in the past will have a switch on the back that says 4 6 8 and you have to just switch it to the correct number of cylinders that your car has and it will adjust to what you need. The pro comp does this automaticly so there is nothing to do. That is it for that. Test as you put them on.
Now I have two more gauges in the car that I dont have a photo of. the third is a clock so nothing big there. The other two are Oil pressure and fuel to air
Oil Pressure you connect to pin 17 on the big connector. Off is 0 ohms and running its 10-90 ohm this is the OK rainge for your car. The Eqquis gauge is a perfect match going 0 to 90 ohms. You splice in there and you will have your pressure.
Fuel to Air Gauge. Now I like to run a hardline right to about an inch above the gauge I have always been to you will get a better reading so you will have to run your own wire to your O2 sensor and plug it in on the back and you are all set there.
I hope this helps any future installs.
Tom
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1985 Fiero GT 4speed 1986 Fiero GT
1994 BMW 530 V8 1997 BMW 328 85 300ZX
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