Hello all I wanted to make a post on how to add aftermarket gauges to your 85GT as there are a few tricks that you can do. There will be no photos as I did not think of adding them till now and I dont want to take the car apart. The main thing here is that the speedo is a one of a kind deal where they had an 85 MPH speedo in the car and not a 120 like the 86 and up GT. The wire colors are not the same for this and there is a trick that you have to do. Now I like the Equus line of gauges and also the Auto Meter Pro Comp light gauges. for this install I have chosen the Auto meters for the speedo and tach and the Equus for the rest other then the air fuel gauge. I might as I can afford them put all pro comp gauges in but they are very expensive to own. The Equess look cloe to them and work great. This is the second car I have used them in. So lets Begin. One thing that is important is the use electronic gauges and not manual this will save you a bunch of time. The Equus series is the 8000 that you should use.
To Begin you will need a few things Wire and terminal connectors. Remove the dash gauges so all that's there is the connectors and since I had no rally gauges I had to install a new set then run wires to them as well. The first thing is that you know you will need a ground a switched 12 volt and dimmer lights. So this is the best first step to take. Run these wires in a chane in and out from one gauge spot to the next. This will only leave the signals from the senders to get. In the ground wire as you daisy chain them you can also connect the grounds for the lights as well. This will be half the battle. Now I went straight of the dimmer witch is a green with white stripe for the lights. All connections for this project can be done at the front harness other then the fuel air gauge.
Volt Gauge. This is straight up install you run one of your switched in and ground the other side and connect the dimmer. Done that easy.
Fuel Gauge. Connect as listed above and then splice into connector #7 on the connector closest to the passanger side. Now the rating is from 0-90 ohms from the stock sender. the higher the ohms the more gas you have. The Equus gauge reads from 0-90 Ohms so there is no sender to have to change you just tap into the factory harness. turn your key on and you will see the gauge go up to where its supposed to be. You are all done now.
Temp Gauge. This is just a splice in as well. The connector on the drivers side is #11. Cold is sits at 0-1400 OHMS and Hot the car is at 55 OHMS. The gauge reads the same way so you just have to tape into the sender and the gauge will run as your stock one. The Equus gauge reads just like your stock one as well so its just a tap in.
This will give you three gauges in the place where the rally gauges go. Now I wanted to keep my idiot lights so I removed all the gauges and bulbs from the casing other then the idiot lights. Super glue will not hold the idiot lights seporator in place so you will have to hot glue them down so they stick. then remove the idiot light gauge covers and super glue them over the bulbs so you will have these lights. Remove all the gauges from the pod ass they are no good to us now looking at our dash we now have to install the speedo and the tach.
Tach. this is very easy to wire. since we daisy chained our wires together we should have all this set to go. connect you 12 volt switched ground and dimmer to the gauge. Now since I am also putting an MSD box into the car auto meter recommends getting the signal from the coil as with the MSD box it it will blow the tach so if you are not putting in an MSD box then you want to connect to #18 on the connector close to the passenger side. This is a 1-6 volt signal. there is no calibration that you need to do on the auto meter gauges so you just plug in and you are set. This Gauge will set itself up and run as needed.
Speedo. This is the hard one to do on an 85GT but now that I know the solution its an easy install. Our cars send out 4000 PPM (pulses per minute) to the speedo to work. 4000 pulses is one mile. Now if you take the old speedo out and tap into the lines you will get nothing zip zero nada. So here is what you do for an 85GT. You need the circuit board from the back for the speedo so remove the old speedo from the board and go out and get some gorilla electrical tape as it is thick and molds itself to what it is covering as you are going to need the board. Splice your In for the speedo to the yellow wire and plug the board back in. Cover the board with the tape so it will not short out and you will be set. Here is the thing. There is a speed buffer on the board and it is needed to send the PPM to the new speedo. Now on most speedo's there is an out on them as well that will goto the cruse and the ecm. You do not have to worry about this as the circuit board still is functioning to do these steps for you. The speedo is now done.
At this point you can be done or you can add a gauge pillar pod to your car witch I have done. So lets fill that up.
Air Fuel gauge There is only three wires to this gauge Switched power Ground and signal. so since we have our three daisy chained wires already there we have two of the three already there to go. Put your switched on and your ground. The purple wire goes to the purple coming off your O2 sensor. I ran this one all the way to the back and taped into the O2 in the rear of the car to get the best signal. And you are done.
Oil Pressure. This will Hook into #17 closest to the passenger side this also read's 0-90 ohms. 0ohms and there is an issue with low oil. 10-90 ohms and you are good to go. Splice the gauge into #17 and you are all set. The equus gauge reads like this as well. so you can splice right in and you are all set.
If you have a three gauge pillar pod then a nice clock at the top. boost if you have that one and or what ever. I am going with a clock as I do not have anything else to tap into till I get some NOS in that car then I will put a bottle pressure gauge in.
I hope this help anybody in the future that is in need of this info.
Thank You
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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