Fuel and Temp gauge wiring questions

Pete

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Sep 17, 2009
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Hailey, Idaho
First Name
Pete
Willys Model
  1. Wagon
Willys Year:
  1. 1960
I'm working on troubleshooting my temp and fuel gauges, neither of them work. It looks like the temp gauge gets it's power from the fuel gauge, so the non-working fuel gauge may have something to do with the temp gauge not working.

The wiring diagrams I have show a fuel gauge with two terminals, one for power and one for the sender. My gauge cluster is newer, and the fuel gauge has three terminals. I did some digging on the web, and found this wiring diagram on a CJ5 site, does this look right?

gaugewiring.jpg


The way my fuel gauge is wired now, is with the sender on #3 as above, but with the hot wire on #2 and nothing on #1. If this diagram looks right, I'm going to move the hot wire over to the #1 position and see what happens. I'm hoping that the guy who wired this didn't already let the smoke out of the gauge... Clearly he should have stuck to spray painting stuff, something he was adept at... :roll:

The #11 terminal on the temp gauge is supposed to go to the temp sender on the block. The guy that had wired mine had the #10 wire for the generator bulb running to the #11 terminal. When the light for the generator came on, the bulb would complete the circuit and send the gauge to "hot". The wire that runs out of the harness to the temp sender turned out to be hot, so I think I fried the sender when I hooked it up.

Seems to me that the temp gauge would work even if the fuel gauge hot wire was on the #2 terminal, which leads me to believe I burned out the sender . Is there any way to test the sender?

Thanks for any insight...

Pete
 
Did some more reading- Looks like the fuel gauge regulates the power to the temp gauge at less than 12v? Connecting the 12v hot lead to the #2 fuel terminal would send 12v directly to the temp gauge through the jumper bar.... Maybe both gauges are toasted... :|

Pete
 
Pete,that's a bit strange,the 3 wire fuel gauge.I'm familar with GM and older Willys with 2 terminals.Interesting theory about "regulated" voltage from one gauge to the other.Some 12 volt vehicles,maybe Ford,use a small "voltage stabilizer" to feed the fuel and or temp gauges.But it's still a 2 terminal gauge I believe.Are you sure the unused terminal isn't a ground? Might be time to pop out the gauge cluster and have a closer look?
 
Here's the info I found on another site. According to this info, my new gauges are likely burned out because the PO wired them incorrectly. I'm going to pull them out tonight and try to determine if they are any good with a tester. Hoping to luck out and maybe when wire correctly they will work.

Fuel and Temperature Gauges
Back of speedometer
Back of speedometer, fuel, and temp gauge

From the passenger side which is left to right in the picture:

* Fuel Gauge S Terminal - pink wire (from fuel sender)
* Fuel Gauge A Terminal - 12v side of jumper strap to temperature gauge
* Fuel Gauge I Terminal - red wire (ignition-on hot 12v)
* Temperature Gauge A Terminal - jumper from fuel gauge A terminal (jumper strap to regulated voltage)
* Temperature Gauge S Terminal - Purple wire (from temperature sender)

SpeedoPic.jpg


Some manuals and gauges have the S and A terminals reversed on the temperature gauge. You can see the letters stamped in the insulation material around the posts. Either way, there is only one circuit loop inside the temperature gauge. The resistance test outlined below is still valid. A fine wire wraps around a bi-metallic strip and the heat caused by the resistance causes deflection of the strip and the connected meter. Like a light bulb, it will work no matter which way the current flows.

The jumper strap goes to a regulator that is inside the fuel gauge. A volt meter applied to the A terminal on the temperature gauge should fluctuate (plus and minus) near 5 volts. A reading of 12 volts on the temperature side indicates a bad regulator. 12 volts applied to the temperature gauge's A terminal will cook the gauge.

The fuel and temperature gauges can be bench tested by connecting a good ground to the gauge cluster and connecting positive 12v to the I terminal of the fuel gauge using a 3 amp fuse. The temperature gauge gets it power from the regulated output of the fuel gauge so the jumper strap connecting the A terminals of the fuel and temperature gauges must be left intact. The gauge needles shouldn't have moved from the off position until you take a resister from the S terminal to ground.

Fuel Gauge

The fuel gauge should have the following resistance ...

* S to Ground 68-72 ohms
* S to I 19-21 ohms
* S to A 19-21 ohms
* I to A Zero
* I to Ground 49-51 ohms
* A to Ground 49-51 ohms

The fuel sending unit wires are located on top of the gas tank where they are hard to get to without dropping the tank. The fuel sending unit should have a pink wire with voltage on the isolated center post. The other black wire on the sending unit with a tab style connector is a ground to the frame. Make sure it has good contact.

To be sure the problem is not the gauge, you can momentarily short the pink wire on the output of the sender to ground, and this should show up as FULL on your gauge. DO NOT hold it for very long in this position, just touch and release the wire. If the gauge does not move from EMPTY either the wiring has an open circuit (no voltage, or no connection to ground) or he gauge is bad. If it does move, the sending unit is bad.

The sending unit can be checked with an ohmmeter to measure the resistance between the round sender post (pink wire) and ground. It should be:

Resistance Reading
73 ohms Empty
23 ohms 1/2 tank
10 ohms Full

If the resistance falls in this ballpark (depending on how much gas you have in the tank), then the sending unit is fine. If it shows infinitely HIGH resistance, then the sending unit could be bad OR the wire from the tank to the gauge could be open.

The gauge can be tested with the resistance listed above. Run an appropriate resistor to the S terminal of the fuel gauge and to ground and check the readings.
Inside fuel gauge
Inside of fuel gauge showing mechanical voltage regulator

There is a mechanical voltage regulator inside the fuel gauge to reduce the voltage to 5 volts for both the fuel and temperature meters. When voltage is applied, the current flowing though the coil generates the heat necessary for the bi-metallic arm to react and open the contact which stops the current. The coil then cools down and the contact closes again. This process repeats itself over and over again.

FuelGaugeInside.jpg


This regulation process reduces the voltage directly to the fuel gauge meter and to the temperature gauge via the jumper strap. A volt meter applied to the A terminal of the fuel or temperature gauge should fluctuate (due to the breaking contact) near 5 volts. There have been reports of this regulated voltage being as high as 7-9 volts with no loss of gauge function. If 12 Volts is applied to the temperature gauge's A terminal, it will cook the temp gauge! (That notorious "puff of smoke").

A 12 volt reading at the A terminal indicates a non-functioning regulator due to the thin coil wire burning out or the contact has welded together giving continuous contact and sending 12 volts directly to both meters, often destroying them. A "0" volt reading at the A terminal can indicate a badly pitted contact which will prevent a voltage going through at all. Both gauges usually need to be replaced at the same time in either case.

Temperature Gauge

The temp gauge has the following resistance ...

* S to A 19-21 ohms

A volt meter can be used to measure the voltage between the A terminal of the temperature gauge and ground. It should be pulsing and averaging about 5 volts. If it reads 12 volts the jumper strip/regulator is bad. If it reads 0 volts, it has been burnt out.

The sending unit can be checked with the following resistance between the post and ground...
Totally Cold High Resistance
Slightly Warm 73 ohms
Beginning of Band 36 ohms
End of Band 13 ohms
Hot 9 ohms

If an appropriate resistor is connected to the S terminal of the temperature gauge and to ground, the above resistance can be used to check the gauge. Use a resistor close to the specifications above to simulate the sending unit.

The temperature sender on 232 and 258 I6 engine is located at the top rear of the engine head. It is near the last head bolt and next to the valve cover on the manifold side of the engine right near the firewall. It is upright and cylindrical with one wire attached to its center post. The sensor's probe extends into the head's water jacket.
 
Yes, i'm in the middle of the same thing with my 61' wagon w/226 engine. Replaced the temp guage and sender first....nothing. talked to Walks....ordered a new fuel guage and talked to the mechanics to be very careful with the install.....i.e. disconnect the battery, etc....stopped by today....still nothing works. The only thing i haven't replaced yet is the fuel tank float, sending unit. Mr. walks said that if you put a test light on the drivers' side of the fuel guage.....that's the terminal that goes to the gas tank sending unit.....it should 'pulsate'. I tried that myself, and it wasn't 'pulsating. it was just 'on'. So my friendly mechanics at the garage are scratching their heads. and so am i.
It's pretty disheartening that something 49 years old, should be this much trouble with a couple of guages.!! At this moment....we're all at a loss, as to what to try next.
 
Spent a few minutes troubleshooting my gauges yesterday. Using the above info, I found that my fuel tank sender is working, and that it is about 3/4 full.

I removed the power feed from the A terminal on the fuel gauge and put it on to the I terminal per the diagram above, hoping for the best. But, as luck would have it, when the previous owner put the power feed on to the A terminal, he unknowingly sent 12v into the internal regulator of the fuel gauge and into the temp gauge through the jumper strap. According the test outlined above, if there is 12v coming out of the fuel gauge terminal A, the internal regulator is fried, and if 12v has gone into the temp gauge, it too has been fried. There should be 5v coming out of terminal A, and it should pulsate as the bi-metalic strip heats up and cools down, cycling on and off. Damn...

These gauges were brand new too, never used. Since it looks like I am now in the market for new gauges, I gave up on this for now and took on getting the heater working. Found all the parts and got them hooked up, and now have some heat...

Pete
 
Pete, sorry about your mishap with the guages :eek: , I'll have to be looking at mine. I got the speedo guage combo from Harry Sheets for around $50 plus shipping.
 
kramwit said:
Pete, sorry about your mishap with the guages :eek: , I'll have to be looking at mine. I got the speedo guage combo from Harry Sheets for around $50 plus shipping.
Who is Harry Sheets? Do you have contact info?

Pete
 
I need to connect my fuel guage too (aftermarket). I know the guages take 5~6 volts, so I was planning on running mine from resistor that feeds the distibutor. It's a '50 that has been converted to 12v. Distributors gets 12v on start and about 6v on run, so just figured I would feed off of that.
Any problems with that?
If not, then Pete could still use his "fried" guages (wont' need his internal resistor).
 
50 dump said:
I need to connect my fuel guage too (aftermarket). I know the guages take 5~6 volts, so I was planning on running mine from resistor that feeds the distibutor. It's a '50 that has been converted to 12v. Distributors gets 12v on start and about 6v on run, so just figured I would feed off of that.
Any problems with that?
If not, then Pete could still use his "fried" guages (wont' need his internal resistor).

I would buy a $19 "Runtz" voltage reducer from Speedway Motors. I used on my my Plymouth and it worked great. It is an electronic voltage reducer, and will prevent voltage spikes.

Pete
 

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Re: Let's go for a ride!

Pete....on my 61' woody, i've been fooling around with my temp. guage and also fuel guage, to get them both working. The fuel guage on these, has some kind of internal regulator, that's supposed to 'pulse'...and cut the voltage down to 3 or 4 volts, and then send that lower voltage over to the temp guage. I took my fuel gauge to the bench....and put 12 volts to it, and grounded the body. Then I put a test light on the terminal that goes to the temp guage, and the test light was 'blinking' on and off, on and off....just like it's supposed to. Then I took a meter, and put it on that same terminal, and it showed 3 to 4 volts coming out. Just like it's supposed to. That lower voltage actuates the temp guage to work properly.
Anyway, perhaps this info will help you with your guages. I'm still in the middle of this area, as I need to replace the fuel tank sending unit...and if I do that, I might go ahead and replace the tank itself with a new plastic tank. so i'm on hold with that project until after the holidays.
I think this is correct information....but if one of the other guys says something different....i've been wrong in the past...(at least once??)
Hope this helps...
Mike
 
Re: Let's go for a ride!

mringg said:
Pete....on my 61' woody, i've been fooling around with my temp. guage and also fuel guage, to get them both working. The fuel guage on these, has some kind of internal regulator, that's supposed to 'pulse'...and cut the voltage down to 3 or 4 volts, and then send that lower voltage over to the temp guage. I took my fuel gauge to the bench....and put 12 volts to it, and grounded the body. Then I put a test light on the terminal that goes to the temp guage, and the test light was 'blinking' on and off, on and off....just like it's supposed to. Then I took a meter, and put it on that same terminal, and it showed 3 to 4 volts coming out. Just like it's supposed to. That lower voltage actuates the temp guage to work properly.
Anyway, perhaps this info will help you with your guages. I'm still in the middle of this area, as I need to replace the fuel tank sending unit...and if I do that, I might go ahead and replace the tank itself with a new plastic tank. so i'm on hold with that project until after the holidays.
I think this is correct information....but if one of the other guys says something different....i've been wrong in the past...(at least once??)
Hope this helps...
Mike

Mike-

I moved your post to this thread that I started a while back about the temp and fuel gauge wiring. As I understand it, you are right about the internal regulator on the fuel gauge. The problem with mine is that the PO wired it backwards, burning out the regulator, and in turn, sent 12v to the temp gauge, burning it out too. These gauges were brand new too...

Pete
 
Thanks to all for this thread and a bump for others to read.

Still testing out my orig gauges, but now at least I understand the voltage reducer in the gauges. Options are new gauges from walcks at about $30 each or apply that to a whole new round panel at about $120.
 
Thanks to all for this thread and a bump for others to read.

Still testing out my orig gauges, but now at least I understand the voltage reducer in the gauges. Options are new gauges from walcks at about $30 each or apply that to a whole new round panel at about $120.
 
Working hard to get the new 60 wagon to Moab. Ran in to a burned up fuel and temp gauge. With reported temps in the 90's for Moab probably not a good idea not to have a temp gauge. I have access to a 1976 CJ speedo cluster. My question is, does any one know if the sending units will work with the later gauges? I assume looking at the back of the cluster the hot lead could go the either side. Dan
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I would imagine it should work. I think the replacement speedometers that Walck's sells are out of a CJ, and they sell them for the pickups/wagons.
 
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