Troubles with my gauge cluster

275hptbirdsc

Registered User
When I bought my 1990 SC last August the owner let me know that the gauges dont light up when I turn the headlights on. After I bought the car he gave me some gauge faces that light up to solve the problem. When I installed them I had no idea what I was doing with the needles so I just carelessly pulled each one off and put the faces on them. I put the needles back on trying to get them to go to their normal places. After 3 hours of struggling I put the cluster back together to test the faces out. The faces worked but my enigine temp,oil temp,gas and boost gauges were off some more than others. My gas gauge was the worst it was completly off. The needle was past F and somtimes even went so far down you couldnt see the tip of the needle.

Fast forward to today I bought a cluster on these forums and I went and put the cluster in my sc that is being stored for the winter. I made sure everything was perfect. I started the car and to my amazment the gas gauge was still off!!!! And to top it off the night lights dont come on either!Heres a picture of the gas gauge im guessing it has just a little bit more the a quarter in there because on my old cluster F usually ment E http://img.photobucket.com/albums/v668/Arbiter1/0226091232.jpg
Now for the lights is there a fuse/wire I should be looking for? My interior lights come on fine if that has anything to do with it. Please I need help.
 
IMHO - The dash lights are controled by way of a rheostat that sits right next to the headlight switch. Replace that and you should be good to go. I bet the interior light doesnt work with the rheostat either.
 
I am wondering - do the lights on the heater controls and radio come on with the headlights?
 
OK, sorry. If they come on and adjust with the headlight knob, there is a wiper and rheostat coil on the switch shaft. To get the knob off the shaft, take a small thin common screwdriver and insert it in the slot at the back of the knob. Pulling the screwdriver toward yourself will release the knob from the shaft. (its been a while since I have been in a 90). Once the knoob is off,the dash trim can be moved out of the way so you can get to the light switch. The rheostat can be removed when the shaft is out of the way. The FLM dealer will have a replacment.
 
I am wondering - do the lights on the heater controls and radio come on with the headlights?

Well the radio I have is not the original one and I havent been in the car for months but I will go out when its dark and see if they come on.


OK, sorry. If they come on and adjust with the headlight knob, there is a wiper and rheostat coil on the switch shaft. To get the knob off the shaft, take a small thin common screwdriver and insert it in the slot at the back of the knob. Pulling the screwdriver toward yourself will release the knob from the shaft. (its been a while since I have been in a 90). Once the knoob is off,the dash trim can be moved out of the way so you can get to the light switch. The rheostat can be removed when the shaft is out of the way. The FLM dealer will have a replacment.

As the car sits right now the thing that goes around the dash is already off and so is the headlight knob so are you talking about the thing the knob is attatched to?
 
The sending unit for the fuel gauge is in the gas tank controlled by the float in the tank----if your gauge is inaccurate but works it may be that the needle on the gauge has just been put on in the wrong place. Its a delicate operation but you may have the hold the gauge axle with a pair of hemostats or something while you move the needle to the correct position. If the gauge is just all goofed up it may be the sending unit in the tank---they do wear out sometimes.............Dan
 
The sending unit for the fuel gauge is in the gas tank controlled by the float in the tank----if your gauge is inaccurate but works it may be that the needle on the gauge has just been put on in the wrong place. Its a delicate operation but you may have the hold the gauge axle with a pair of hemostats or something while you move the needle to the correct position. If the gauge is just all goofed up it may be the sending unit in the tank---they do wear out sometimes.............Dan

Well now that you say that it could be the floater because the fuel gauge is messed up on two clusters and they both are in the same place.
 
Well now that you say that it could be the floater because the fuel gauge is messed up on two clusters and they both are in the same place.

You may or may not need to replace the sending unit. You can actually bend the float arm to compensate somewhat, but there is a limit. I would recommend that you check the resistance of the sending unit with a multimeter as you operate the float arm.

If you are going to open up the tank, you should replace the fuel pump. Dropping the tank is enough "fun" that you wouldn't want to do it again in 3 months.
 
There is a circuit board on the side of the cluster that controls the fuel gauge. Make sure it is seated firmly and that the contacts are clean.
 
I just drove the car tonite because my winter beater took a dump and no the heater controls do not light up when the lights are on.

Ok, then it sounds like you have a wiring problem, as you suspected before. I don't have my wiring diagrams with me, but I could look into it later. One initial thought is that maybe someone shorted the instrument illumination out when they installed the aftermarket radio.
 
Ok, then it sounds like you have a wiring problem, as you suspected before. I don't have my wiring diagrams with me, but I could look into it later. One initial thought is that maybe someone shorted the instrument illumination out when they installed the aftermarket radio.

OK thanks for all your help. I will be looking out on this thread the next couple days cause I have Wed and Thursday off and I am planning on getting my car back up to what it used to be before I stored it.
 
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