I've tried to ask about my situation in another thread, but was getting confusing between 6v systems, 12v conversions with stock gauges, and 12v systems with 12v aftermarket gauges. So thought I'd ask in a new thread.

I purchased the aftermarket 1953-55 fuel gauge and sender from MidFifty.
"Gauges have same modern technology as new aftermarket gauges but look and fit like original. Fuel gauge uses resistance range of 240-33 ohms."

Gas tank and wiring harness are from a 1994 Ranger. The instrument cluster is a 1954. My problem is that the new fuel gauge was always reading half full. I got another new gauge and this one is always reading quarter tank (even after I filled the tank). If I ground the sending terminal, both gauges peg to full (as indicated in the troubleshooting instructions). The sending unit in the tank was tested before going in and the ohm levels seemed to be in range.

I decided to do a bench test with the gauge, new 240-33 ohm sending unit, and a car battery. Hooked it all up and the gauge reads "full" until the sending unit lever is pushed all the way down (empty) and the gauge reads around "3/4". Since the bench test isn't working correctly either, I'm hoping someone on here could help identify the problem or give troubleshooting suggestions.

(On a side note, I used the matching battery gauge and it seems to be working fine.)

 

That float arm looks awful long. Could it be hanging up on an internal baffle? Does that arm pivot at the bottom?

 

lets take a few steps back

the sending unit is not concerned with the voltage of your system. All it dose is give a variable resistance of 240-33 ohms to ground. That being said its important that there is proper grounding for it to work properly this is easily accomplished by the mounting to the tank and the tank to the body or frame. Secondly the float needs to move freely to swing the sending unit through its "range". I would suspect this is where your problem lies.

The gauge end is in simple terms a meter reading the resistance from that sending unit, with the F 1/2 E readings pre calibrated by some electronic geniuses that know far more than you or I. They do care what the voltage is I've herd that ford still used 6V clusters well into the 90's so it would be prudent to know if at the heart of the original ranger cluster if it was 6 or 12v, maybe some research on your end to make sure its all jiving up.

It should be a simple install power to gauge (gauge grounds via mounting in cluster) and a single wire preferably with soldered ends straight to the gauge. My sending unit also has a condenser of capacitor going from the sending unit to a mounting bolt, i think this is to smooth our the needle reading to make it less jittery

 

Float arm is universal. You simply cut it to length. I cut mine to the same length as the one removed. I also tested that it didn't hit an internal baffle.

If I didn't have 2 of the same gauges and got different results, I'd think that the problem lies in the sending unit. However, one gauge always reads "half" and the other gauge always reads "quarter". (Nothing else has been changed when switching out gauges.)

As I explained, the third scenario was the bench test. I can not get it to operate properly out of the truck either.

 

I know something that is fairly simplistic shouldn't be this hard!
As far as I know, the circuit consists of the sending unit in the fuel tank (new); the gauge in the dash (new), and the tank wiring and dash wiring that connect them (1994 Ranger).

The new gauge has 3 push on terminals - Positive, Negative, Sending.

I didn't install the wiring harness and the instrument cluster is all 1954. Just read on a Ford Ranger site: "The gauge uses a 5 volt pulse supplied by the instrument cluster's voltage regulator." So if the voltage regulator is in the stock Ranger instrument cluster, my truck wouldn't have it. If it is regulated in the electronics/ computer, then maybe this is the culprit. I do have power at the positive terminal when I turn the ignition key, but I did not put a tester to test the voltage.

Ground: I would assume that there is ground because if it was grounding out, it would pegged at full, or not working at all. The gauge is additionally grounded by the instrument cluster/ dash. Are there other grounds I need to check? (I have previously checked/ added grounds from engine to frame, engine to body, box to frame.)

Resistance: Sending unit is 240-33 ohms; gauge is 240-33 ohms. I had a garage test the sending unit before it went in the tank. However, I haven't tested what the ohm reading is currently at the gauge. (I don't have a way to manually operate the sending unit inside the tank without taking the truck back apart.)

I don't think I have anything like this. I also don't have any resistors on the instrument cluster.

 

I don't think the mid-50 unit uses that Ranger's style of pulsed power.

When testing, either on the bench or in the truck, do you have a ground wire to the sending unit's body? The tank is "theoretically" grounded, but also mounted in rubber.

 

Hi
As was commented on this gauge would have to be 6v to that gauge same as the install I'm planning. On early fords there was a mechanical bimetallic switch but by 94 they changed to a module that accomplished this. I would bet that should straighten it out for you. There was also a anti slosh module.... just basically slows down the needle from bouncing if it was in a ranger I'd say that could be the problem but since your running your old wires I'm assuming you have removed that.... please keep us posted on what fixes it
I might be fighting with mine next. :-)
Zac

 

I will have to pull it apart and figure out how to test the voltage. I'm pretty sure it is 12v with ignition, but I could be wrong. When bench testing, I know it is direct from battery and the mid-fifty gauge is not acting correctly either.

Testing:
In the truck - there is a built in ground in the gas tank sending unit wiring harness.
Bench test - Yes, I ran a ground wire from the sending unit direct to negative terminal of the battery. Another ground wire from battery to gauge. Wire from positive terminal to gauge. Sending wire from sending unit to gauge.

 

Sorry after Ross post I reread your question and see you bought the gauge from mid fifty. I'd just give them a ring, find out for sure if it's ok straight 12v. Some gm like 7v, old Porsche 3??v Ford 5-6v. Better to hear right from them and if they say 12v and your ground is good I'd say your sender is bad. There is a tool that most shops have it's a little box that has an adjustable potentiometer.... you hook up your gauge go through the range and if it's good ....your then sure it's the sender.
Zac

 

Do you know where the anti slosh module be located? Willing to try anything at this point!

Do the new Midfifty gauges that are 12v still need the old style reducers? (The battery gauge didn't seem to need it.)

Thanks for the input everyone. One of those problems that has me stumped (and ticked off).

 

Thanks Zac. I have 2 calls into Midfity. They were supposed to look into it and haven't got a response yet. Figured someone on this board must have used these gauges before. I have two $95 complete fuel gauge kits, both read different (vary by 1/4 tank), and neither correct. Sender should be the easier test - variable resistance measured by the ohm output. Thought if I get it working out of the truck via bench test, I could replicate in the truck (running new power wire, ground, or sending wire if needed). But thus far, even the bench test has failed.

 

I have the same gauge and sending unit in my '53. When I first installed, it didn't work. I checked connections, check continuity, etc. ... nothing. Went thru the Midfifty Trouble shooting guide. Gauge check and sending unit seemed to work... finally took the whole thing out and bench checked, still incorrect readings. I was about ready to give up .. checked it one more time making sure I had good connections and Shazam it work just like it was supposed too.. I figured out that the sending unit arm was a slight bit loose and was not making good contact.
I tightened things up and reinstalled worked great ever since..YMMV

 

Thanks for the input! I was starting to think I was the only one to have an issue. I will certainly give that a try tomorrow. Just to double check - how did you bench test it?

 

I used 12v motorcycle battery, one jumper wire (+) terminals gauge to BAT, (-) terminals, I hooked the gauge and sending unit together then ran another jumper to the BAT, one more jumper sending unit to gauge.

The issue was the float was loose where it connect to the sending (the end you shorten) it was forcing the contacts on the graduated scale to loose some contact. I re-bent the float arm and make it was secure and all worked normal.

 

Hey BT, I noticed that you stated on another thread "gauge grounds thru housing" FYI this is not correct for the midfity gauge. The (-) terminal on the gauge MUST be grounded. I grounded all my gauges (-) terminal to a common bolt behind the dash.