I honestly don't know which thread it came from. I saved it to a word doc 5/16/06 it used 110/50 ohm resistors which I bought two sets of last year, here is that doc:
Remove the gauge from the cluster. first the cluster splits in two, the gauges and a white backing are one half, the "glass" and black mask in the other. There are clips around the perimeter lift each one in turn by hand and the two halves will split, after the glass is off be careful not to set the cluster on its face, the cards and needles are kind of fragile. Try not to not touch the face cards of any of the gauges, fingerprints leave marks, there are 4 screws (see pic) back these screws out partially and then press them with moderate finger pressure. the gauge will seam stuck at first but then will pop up a little bit, if is fells wrong or partially attached stop and give it a good looking over, completely remove the screws and then work the gauge out, it had some slight interference with the tack card but it can be worked out of there. Be careful the tach needle does not receive any load.
Modify the gauge
If you do not know how to work with solder give these a read
http://www.circuittechctr.com/guides/7-1-1.shtml
http://www.epemag.wimborne.co.uk/solderfaq.htm
First need to secure the gauge so that you will have two free hands but the gauge is not resting on the needles, there is an area of the PCB that can be clamped in a vice at a corner, when you need to apply even light force to the PCB also support it with your hand, do not bend the PCB.
More secure clamping method provided by Rookie2
https://forum.ih8mud.com/showpost.php...4&postcount=58
The two components we are interested in are a 75 ohm resistor and a Zener diode (see pic) both of these have two connections each for a total of 4 connections, the resistor looks somewhat like a peanut and is just over ¼” long on the back of the PCB it is marked with a zig-zag line , the zener diode is a tiny red bead it is marked on the PCB by a rectangle with a stripe at one end.
First we need to remove both of these components, de-solder these 4 connections straighten out the wires and push them through, if you have any troubles with them hanging up on solidified solder use the tip of your soldering iron. Using the soldering iron as a tool is handy as it will keep the solder flowing wile you move stuff around. Then remove any excess solder as necessary to have the holes open to allow insertion of the new components, a small amount of solder left on the pad of the PCB is acceptable and actually desirable.
The 110 Ohm resistor will replace the 75 ohm resistor; first bend the leads of the resistor to until they are parallel to each other and perpendicular to the resistor. You do not want to bend them tight right as it comes out of the resistor, this may form cracks in the wire that could cause the lead to break with vibration rendering the gauge useless. Set a ~1/8” drill bit against the resistor touching both the resistor and the lead, bend the lead 90* over the bit this will form a radius. You want the two legs spaced as close as possible to the width of the two holes in the PCB, trim the two leads just enough to get between the PCB and the face card of the gauge, This resistor can get hot in use so we want air flow around it, we also want to keep it away from the clear plastic light guide and the needle motor, I let it naturally hang with gravity and put it closer to the PCB (but not to close) than the face card and it seamed about right (see pic) solder it in place then trim the excess lead.
The zener diode is replaced with the 50 ohm resistor. The holes for the zener diode were smaller than the leads of the resistor, chuck up a very small drill bit (same size as the lead of the resistor) in a drill and turn the chuck by hand to enlarge the holes. These holes are closer together than the width of the resistor so you will need to bend one of the legs into a joggle, make a180° bend at the end of the resistor then a 90°bend at about the middle of the resistor, bend the other one 90* at a location that will achieve proper spacing, trim the leads so that more than enough will go through the hole to support the resistor. this resistor does not get hot and due to its location is easier to install this one on the bottom of the PCB opposite of the other resistor. There is clearance in the cluster to do so just keep it tight against the PCB (see pic)
If you have a meter check the connections. the resistance of the joints should no be more than 1 ohm higher than the resistance you get with your probes touched together, Check the resistance from the sense post (top post in the pictures) to the two close legs of the two resistors, the other leg of the 110 ohm resistor is checked to the + post (lower left in the pictures) , the other leg of the 50 ohm resistor is checked to the nut marked “U”, there is a thin coating on the nut you need to pierce to make a connection
Results
You now have a gauge that will move with all temperature changes within its sensitive range.
Full sweep peg to peg is 94°
Pegged hot 244°
Top of red is 227°
Bottom of red 217°
Center is approximately 189°
Cold line is 160°
Pegged cold 150°
Notes
“Center” is pretty much horizontal. It is the middle between the bottom of red and the cold line, witch is not the same as center of the full range of the gauge. Some describe “center” as the just below the middle, also the needle sits high above the face card with the markings making it quite susceptible to parallax error, at any rate after warm up wherever your needle sat before mod is the “center” point for our purposes.
Please give feedback on how this goes for you. And what changes can be made in the directions to make it clearer. If you find any tips or tricks along the way please post 'um up
93-94 trucks Thanks to the effort of Semlin a mod is in the works.
Edit 3-15-05, the same mod also works for 93-94 trucks within a few degrees, accessing the gauge may be a little diffrent as the dash is diffrent on the 93-94 trucks, if anybody does one of these would you mind taking notes on accessing the guage.
not dangerous but not right. the normal op temp according to my FSM is up to 203.
