B&M Transmission Temperature Gauge in a Cherokee
	Category:	Electronics
	Author:	MachineMan
	Date:	March 4th, 2005

This write up explains how to install an automatic transmission temp gauge using an electrical sending unit mounted inline with the cooler lines. This write up is based off a 1990 Jeep Cherokee 4.0L 4x4 with AW4 tranny. Other years may vary slightly.

Parts
I opted to use a tranny Gauge from B&M (part# 80212) which came with gauge, electric sender with wire, and compression fittings. I ordered mine from Summit Racing which was about $46. You can use a different gauge kit but this one came with everything and fits where I wanted to mount it. www.summitracing.com Search "gauge electric"

Gauge Kit bmm-80212


Dash Mounting (2hours)

1. I dash mounted mine in that useless space below the clock. By doing this you will not be able to use the clock anymore. My clock didn’t work and my radio has one anyway. If you plan to mount the gauge using the supplied bracket than skip this section.
   
2. Remove dash bezel by taking out the four screws and carefully pry it out of the retainer clips.
   
3. Unscrew the clock panel mount (3 screws) and unplug.
   
   
   Dash taken apart
   
4. Remove the clock panel and grind the 4 black nubs off the back that hold the black faceplate. Separate the black face and clock case. Note that different years have different clock assemblies. There’s some pics of different models at “Go Jeep” http://www.go.jeep-xj.info/HowtoDashClock.htm
   
   
   Stock clock wiring and PCB
   
5. Unscrew the clock PCB off and separate the lamp leads. You should be able to completely disassemble it with out breaking anything. Also note that the clock buttons and LCD display will fall out.
   
6. Mark the center of the recessed black panel. Measure it carefully because the 2- 1/16” gauge barely fits.
   
7. Put the black face back on the clock case and drill a pilot hole through both sides. Then drill a 2-1/16” hole through both. I could only find a 2” hole bit so I used a file to open it up a bit more. Use whatever temp gauge you purchased to see if it slides in. Make sure to stay centered and not crack the plastic pieces. When you’re done it should look like this.
   
   
   Drilled 2+ inch hole
   
   
8. Now glue the LCD assembly (not the PCB board) into the face to cover up the clock hole. You won’t be using the PCB anymore.
   
9. Put the black face and clock case pieces back together and slip the gauge in.
   
10. Trim the sides off the gauge retainer and tighten the gauge up. This will also secure the black face and clock case together.
    
    
    The gauge in the clock panel
    

Wiring (1hour)

1. The gauge is easy to wire. The B&M gauge needs; Ignition power, neg. Ground, Lamp power, and the sender wire. The usable wires from the clock panel connector are ignition power and ground. It does not have a switching lamp power because the clock lamp turns on with the ignition regardless of the lights being on. The best thing to do is use a multi-meter at the dash connector to check which ones are ground and which have 12V only when the ignition is on. Other brand gauges will be wired similar to this one and if you mount it somewhere else it will be the same jut not using the clock connector.
   
2. Cut the plug with leads off of the clock PCB and wire up the ignition power and ground to the gauge. I removed the pins that I don’t need from the plug. Use the schematic that came with the gauge to determine which lugs to use. The lamp power and sender unit will be wired separately.
   
   
   The gauge installed into the clock panel
   
3. Now plug it into the dash clock plug. The lamp power will have to be spliced into an existing wire. I used the orange/black wire which runs nearby to the cig. Lighter lamp. Feed the sending unit wire through a grommet in the engine firewall.
   
   
   Dash wiring
   
   
4. Put the dash back together and see how sweet it looks!
   
   
   Finished dash mount
   

Sending Unit Installation (1hour)

1. This is where you can cripple your vehicle if you don’t do it correctly. Locate the auto transmission pressure line to the cooler. On my tranny it is the one coming out at the front of the transmission.
   
2. Assemble the sending unit into the compression tee. I put some Silicon sealant on the sending unit threads. The B&M gauge comes with all the required fittings and for the Jeep it uses a 3/8” compression fitting.
   
3. Clean the area where you are going to cut the tube. Use a small pipe cutter to cut the line. You can use a hack saw but be careful about metal burs getting into the lines. Then cut it again removing about a ¾” piece so you can put in the 3/8” dia tee compression fitting. Some tranny fluid will come out but not a whole lot.
   
4. Tighten it all up and hook up the sending unit wire with the supplied ring lug
   
   
   Sender fitting
   
5. Start up the vehicle and check for leaks. Also check your tranny fluid level just in case you spilled too much. Drive it around and test out your gauge!!
   

Tom K. Feb. 2005