Water temp and fuel gauge problems
-
Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.To dismiss this noticeclick the top right X.
Water temp and fuel gauge problems
- Thread starter PDR
- Start date
Sasquach
Crazy Sr. Respected Jeeper
- Posts
- 4,054
- Media
- 35
- Thanks
- 2
- Location
- Santa Ynez, Ca.
- Vehicle(s)
- 1978 CJ5, 258 w/4.0head, Mopar MPI, P.S., P.B.,Tilt wheel, No stereo, t-18, t-20, amc 20, dana-30 w/tru-trac, Warn full float w/locking hubs & Detroit locker in the AMC.
1964 CJ3B, 4-134
1952 M100 trailer
how are the connections on the back of the guages? loose wires/no ground that sort a thing.
BusaDave9
Always Off-Roading Jeeper
- Posts
- 8,248
- Media
- 360
- Resources
- 2
- Thanks
- 88
- Location
- Durango, Crawlarado
- Vehicle(s)
- 1979 Jeep CJ5 with 304 V8, T18 Transmission, Dana 20 Transfer case with TeraLow 3:1 gears, 4.88 axle gears, Detroit Locker up front and Ox Locker in back with 1 piece axle shafts, 36" SuperSwamper SX Tires, Shackle reversal, MileMarker Hydraulic winch, MSD 6A ignition.
The water temp gauge and the fuel gauge both use the same +12 volt line. I am willing to bet dimes to donuts that is where your problem is. There is a red wire going to the assembly that should have at least 12 volts when your ignition is on.
Edit: now if you don't have 12 volts on that red wire you need to track down where you are loosing it. That same 12 volts should drive the brake light on the dash. Put on your parking brake. If that light comes on then the problem is in the dash. If it doesn't then the problem is most likely the big connector on the drivers side where the wires go through the firewall.
Worse case if you can't find out where the wiring is going bad you can route a new wire to the water temp gauge and the fuel gauge assembly. You will want to make sure it is switched 12 volts that only comes on when the ignition is on. The 12 volts to the radio would work out good.
Edit: now if you don't have 12 volts on that red wire you need to track down where you are loosing it. That same 12 volts should drive the brake light on the dash. Put on your parking brake. If that light comes on then the problem is in the dash. If it doesn't then the problem is most likely the big connector on the drivers side where the wires go through the firewall.
Worse case if you can't find out where the wiring is going bad you can route a new wire to the water temp gauge and the fuel gauge assembly. You will want to make sure it is switched 12 volts that only comes on when the ignition is on. The 12 volts to the radio would work out good.
Last edited:
PDR
Jeeper
Ok, After determining that the brake light comes on. I located the large red wire coming into the gauges. It show 12 volts with the ign on. I guess there is a ground problem in the dash. Would running a new grnd wire to the gauge cluster work. Thanks again.
BusaDave9
Always Off-Roading Jeeper
- Posts
- 8,248
- Media
- 360
- Resources
- 2
- Thanks
- 88
- Location
- Durango, Crawlarado
- Vehicle(s)
- 1979 Jeep CJ5 with 304 V8, T18 Transmission, Dana 20 Transfer case with TeraLow 3:1 gears, 4.88 axle gears, Detroit Locker up front and Ox Locker in back with 1 piece axle shafts, 36" SuperSwamper SX Tires, Shackle reversal, MileMarker Hydraulic winch, MSD 6A ignition.
No, the sending units are grounded not the gauges. In other words here's how the circuit works: 12 volts is supplied to the gauges. Current flows through the gauge to the temp sensor (or fuel sending unit) and this sending unit supplies the ground.
I still think the problem is the 12 volts at the gauges. If I am wrong there are 2 problems (2 bad gauges or 2 bad wires to the sensors)
If I remember right there is a metal piece that connects both gauges together. Then this metal piece has the connector for the 12 volt wire. I assume you disconnected the wire to read the voltage. I know it is hard working under the dash but would it be possible to read the voltage on the gauge when everything is put together?
I think there are possibilities: either this 12 volts is shorted to ground or there is an bad connection at the gauges.
If there is a short you blew that fuse you already replaced. Check it again.
I think it is very possible that we have a bad connection between that 12 volt wire and the gauges. Look over how 12 volts goes into those gauges. Take it apart and put it back together again if necessary.
CJ
Admin
- Posts
- 22,327
- Media
- 762
- Resources
- 193
- Solutions
- 36
- Thanks
- 734
- Location
- Central FL
- Vehicle(s)
- '72 CJ5, 401, T18, D20, D44, D30
'82 CJ8, 258, D300, AMC20, D30
Check out the 2nd and 3rd section of this post for some great gauge trouble shooting info...
http://www.jeep-cj.com/forums/f49/useful-info-thought-id-share-665/
PDR
Jeeper
I tested the red wire disconnected from the gauge with a test light (bright). I also tested the (I) teminal of the gauge with the test light, also bright. I will put the volt meter on now and make sure I am getting 12 volts. At the gauge. As you mentioned the (A) terminals of each gauge are joined with a metal strap. I wonder if a bad ground has damaged both gauges?
BusaDave9
Always Off-Roading Jeeper
- Posts
- 8,248
- Media
- 360
- Resources
- 2
- Thanks
- 88
- Location
- Durango, Crawlarado
- Vehicle(s)
- 1979 Jeep CJ5 with 304 V8, T18 Transmission, Dana 20 Transfer case with TeraLow 3:1 gears, 4.88 axle gears, Detroit Locker up front and Ox Locker in back with 1 piece axle shafts, 36" SuperSwamper SX Tires, Shackle reversal, MileMarker Hydraulic winch, MSD 6A ignition.
A light is usually good enough.
Did you check the A terminals? That is where the 2 gauges are tied together. That should be 5 volts and light the light although not as bright as the 12 volt test. If you don't have voltage at the A terminal your fuel gauge may be bad. The fuel gauge steps the 12 volts down to 5 volts before sending it on to the temp gauge. For that reason a bad fuel gauge may make both gauges not work.
If the A terminals check okay you can also check the resistance going back to the 2 sending units. CJ and BrockGrimes had some excellent links. Go to the bottom of this link Troubleshooting Jeep CJ Gauges and Senders to see what resistance you can expect.
Did you check the A terminals? That is where the 2 gauges are tied together. That should be 5 volts and light the light although not as bright as the 12 volt test. If you don't have voltage at the A terminal your fuel gauge may be bad. The fuel gauge steps the 12 volts down to 5 volts before sending it on to the temp gauge. For that reason a bad fuel gauge may make both gauges not work.
If the A terminals check okay you can also check the resistance going back to the 2 sending units. CJ and BrockGrimes had some excellent links. Go to the bottom of this link Troubleshooting Jeep CJ Gauges and Senders to see what resistance you can expect.
fitzp20102
Jeeper
- Posts
- 43
- Media
- 6
- Thanks
- 0
- Location
- Burtonsville, MD
- Vehicle(s)
- 83' CJ-7 258 with MOPAR FI kit 44 rear from Scout-locked F&R 36" Swampers-trail ride only, 78 CJ-7 258 stock all around street ride, '42-2A work in progress
That's a great article from John Foutz. Invaluable in troubleshooting I would say. Let me ask this on a related subject. While doing the same troubleshooting we are discussing here, I noticed that my 4WD light says "Emer. Drive". Anyone else got that? Its a 78' CJ7 . Also, looking at the replacement gauge clusters shown in all the catalogs, it looks like mine is reversed. My "Brake" light is on the left and my "Emer. Drive" light is on the right. The catalogs show it the other way around. Thoughts?
fitzp20102
Jeeper
- Posts
- 43
- Media
- 6
- Thanks
- 0
- Location
- Burtonsville, MD
- Vehicle(s)
- 83' CJ-7 258 with MOPAR FI kit 44 rear from Scout-locked F&R 36" Swampers-trail ride only, 78 CJ-7 258 stock all around street ride, '42-2A work in progress
My Gauges...
BusaDave9
Always Off-Roading Jeeper
- Posts
- 8,248
- Media
- 360
- Resources
- 2
- Thanks
- 88
- Location
- Durango, Crawlarado
- Vehicle(s)
- 1979 Jeep CJ5 with 304 V8, T18 Transmission, Dana 20 Transfer case with TeraLow 3:1 gears, 4.88 axle gears, Detroit Locker up front and Ox Locker in back with 1 piece axle shafts, 36" SuperSwamper SX Tires, Shackle reversal, MileMarker Hydraulic winch, MSD 6A ignition.
fitzp20102
Jeeper
- Posts
- 43
- Media
- 6
- Thanks
- 0
- Location
- Burtonsville, MD
- Vehicle(s)
- 83' CJ-7 258 with MOPAR FI kit 44 rear from Scout-locked F&R 36" Swampers-trail ride only, 78 CJ-7 258 stock all around street ride, '42-2A work in progress
Yes. True. Dana 20 has no 4WD switch to illuminate a light. Which is why it is even more odd that I have this instrument cluster. But I'm pretty sure you could get QuadraTrac in 78'. A friend of mine who is a venerable Jeep God here in Maryland says that in those days they virtually threw in any one of many gauge variations they had.
Rescue Diver
Full Time Jeeper
- Posts
- 1,779
- Thanks
- 0
- Location
- Kansas City
- Vehicle(s)
- 1979 CJ-7 with a fiberglass body and 1982 wide track axles, 258 I-6 with a 1995 4.0 head, HEI distributor, Motorcraft 2100 Carb, T-18 wide ratio tranny, Super Lift Springs and 33s, a 1997 BMW 328i, and a 2010 REDLINE CONQUEST TEAM Cyclocross Bike. :)
Older CJ's have the emr drv light on the right instead of the 4wd light on the left. They only work with a QuadraTrac in those years. When jeep went to the Dana 300 they switched the brake and emer drv lights from one side to the other, changed it to 4wd and put a switch in the Dana 300 Transfer Case .
Back to the gauges not working. You need a really clean ground where the fuel gauge contacts the speedo housing. There are bumps in the housing that contact the back of the fuel gauge. If the fuel gauge isn't well grounded, it will burn out the regulator inside the fuel gauge within a couple seconds and cause both the fuel and temp gauges to stop working. They all recommend that if you replace one gauge you should replace both as a matches set.
Moral to this story is, if you replace these gauges, make sure you have a really good ground or you'll be replacing them again right away. I learned this lesson the hard way. I hope this post helps keep others from doing the same.
MN CJ7
Senior Jeeper
- Posts
- 636
- Thanks
- 0
- Location
- MN
- Vehicle(s)
- 1978 CJ7
Silver paint with black hard top on 33" radials & eagle alumium rims. Good looking ride and have done lots of work to make it look and run great.
Stock equipment is 258 carb, power brakes, power steering, hard top & hard doors (per vehicle gross weight) tilt steering wheel, big brake package with large rotars & drums, T18 Trans with low 6.4 granny gear, Dana 20 transfer, Dana 30 front axle, Dana 44HD rear axle with 3.73 gears. True Trac ft & rear.
I was around jeeps in the 70's and drove a 1973 Jeep Truck. My family had 4 jeeps at the time. We also joined a jeep club back then too. So about 6 years ago looked for a Jeep CJ and found the vehicle above.
Hi,
Was helping another TEMP Gauge Sender thread and saw yours at the bottom of the page...
If you did not get your temp gauge settled this may help you. Mine did not work right so I went looking... This is a very good solution.
I ran into the same problem on my 1978 CJ7 the temp gauge read but barely reached the green when at temp. When I looked at the TEMP sensor range in the Jeep FSM it did not match the sensors installed, mine looked fairly new, and did not match what I purchased at Napa...... So I went looking and this will solve your problem if you want to use the stock stuff...
I wrote this a few years ago...
TEMP SENDERS are also a issue. I purched 3-4 inexpensive units and the temp/reistance range was not correct. I ordered Napa's premium unit, ,Elchin? Brand, double the price, and boiled it in water prior to install to test, can also be returned as new if does not pass test, and the boil waster is 212 Deg F or very close and will have a resistance value about 35 ohms. Take it out of boiling water FAST put on paper towel, something that is not a heat sink, and measure the resistance with a multimeter. This needs to be done FAST you will see the resistance change in seconds. Thought I would throw this into the conversation about CJ gauge solutions.
My Temp gauge was bairly reading with PO set up. That temp sender and 3-4 more all failed till I tried the Napa Elchin premium version for the CJ Temp Sender. That one measured correctly.
I have seen the pressure and temp issues dozens of times.
Hope that helps.
the Oil Pressure Gauge and Sender has a similar issue. I have a write up for that also...
Jeepeagle
Jeeper
I've got an aftermarket water temp gauge, non electric, and it works fine, but I can't get my fuel gauge to stop reading "full". If it was some voodoo magic, and my Jeep got the world's best gas mileage I'd be happy, but I know that's not the case.
At first I tried fuses, checked ground, all the things suggested, and have determined that the gauge is fried. It reads full when the vehicle is off, and all wires are disconnected.
As a temporary solution, I bought a Sunpro fuel gauge from AdavnceAuto, and it reads full, but only when the Jeep is turned on or running. I know the ground is good, I've got it wired directly to batterie's negative terminal, and I know it's getting 12v.
Could the sending unit be stuck, or busted? If so, is that a DIY job?
Thanks.
At first I tried fuses, checked ground, all the things suggested, and have determined that the gauge is fried. It reads full when the vehicle is off, and all wires are disconnected.
As a temporary solution, I bought a Sunpro fuel gauge from AdavnceAuto, and it reads full, but only when the Jeep is turned on or running. I know the ground is good, I've got it wired directly to batterie's negative terminal, and I know it's getting 12v.
Could the sending unit be stuck, or busted? If so, is that a DIY job?
Thanks.