Fuel Gauge - Reads Full

[ymelnic1]

Hello all! I have gone through a few threads regarding the faulty fuel gauge, but have not seemed to resolved my issue and am wondering if someone can help.

My fuel gauge is pegged at Full. I have a new sending unit and new IVR on the cluster. The + wire to the IVR reads 15.5 volts. The ground wire to the negative post of the gauge is properly connected. I have even bypassed the original orange wire from the pigtail at the sender unit with a new wire going from the sender unit post directly to the cluster fuel gage. I have cleaned the ground wire at the sender and made sure the wire is properly connected.

Something else to note when I turn the key to the OFF position, the gage goes down but has a very slight tick or "spike" around 3/4 full tank and then continues to go down past E.

I have just hooked up the Multimeter to see the reading at the post per previous threads, and the unit reads 1.6 ohms at the "200" ohm setting on the multimeter. The tank is full. Per the earlier threads, it should read somewhere around 16 ohms.... am I doing something wrong here?

Thanks and Happy Easter!

 

[Broncobowsher]

Unplug the wire of the sending unit, do nothing else. Does the gauge still peg?
The voltage reading on the IVR, is it steady or does it blink on and off like a turn signal?
15.5V is a bit on the high side. What is the battery voltage while running? What alternator are you running (stock or some upgraded)?

 

[ymelnic1]

In the ACC key position -

The peg does not occur once the wires are disconnected at the sender. The reading falls to below E.

I have an aftermarket IVR with two posts for the 12V (15.22v in my case) wire. With the hot wire connected to one post, and taking a reading a the other post and the ground terminal at the IVR, I get a steady 15.22 +/- reading

The 17.6v at the battery while running. Aftermarket alternator (specified stock not upgraded).

I have it plugged to a battery charger while in garage.

 

[Broncobowsher]

The 17.6 running indicates another problem, you are overcharging the battery. The voltage regulator is bad.

The IVR also sounds bad. It may have been fried from the bad (charging system) voltage regulator. also the aftermarket IVRs are also will known for poor quality so it may just have been a bad part.

At this point don't run the engine on the truck anymore. You are destroying the battery with the overcharging. Work on that problem first. While at it leave the sending unit wire off at the tank. No need to accidently burn up the gauge until you get a chance to work on that. Once you have the charging system on the truck working right, now go back and work on the IVR.

The voltage regulator (charging system) is sensitive to bad grounds. If it isn't well grounded it doesn't have a baseline for what the voltage in the charging system is. Like sticking a volt meter on a battery terminal without the ground on anything. It doesn't see voltage, so it spikes it. That spiking still burns up the regulator.

 

[ymelnic1]

I'm going to re-ground the regulator tomorrow with a proper location to see if it helps or I need to replace it all-together. As of right now it's grounded to the firewall?? I've also ordered a new IVR from Tom's. like you said I won't mess with the IVR until I fix the Regulator.

an you advise on what readings I should be getting at the hot wire going into the IVR and at the battery terminals while the truck is running?

Thanks for your help!

 

[oleguy74]

with everything right,13.5volts with engine running.so that is what you should see at ivr.here are some specs:all wires removed from gauge 10-14 ohms across gauge.gauge range is 10 ohms full,73 ohms empty.also to test ivr,leave power connected,connect a test lite to ivr output.if lite flashes like a turn signal,ivr should be ok.if no load is connected to ivr output it wont puls.

 

[figo40]

Output on that voltage regulator should be lower than charging voltage. 3.5 to 6 volts should cause the guage to function properly.

 

[Broncobowsher]

13.5 to 14.2 or so is a good range while running. You can get deep into theory and battery types if you really want to. There really isn't a black and white answer on the exact correct charging voltage. 12s is too low, 16+ is too high. 15s are sometimes desired but generally not long term.

IVR comes in two versions. The old "blinks" the power to average about 5V. There is some temperature compensating built in so when it is hot you may only average 4V and in the dead of winter at first start up you might average 7V. There is a solid state version (an LM7805 if you ever want to try and build your own) that is a steady 5V output. Gauges may be a bit off in very hot or cold conditions, but you will get some form of gauge that is generally just fine for a hobby car.

 

[ymelnic1]

I put in a new voltage regulator today. Got one at Auto Zone. I have discovered that my alternator was grounded via 14ga wire with the screw to the firewall that attaches the VR to the fire wall. I have drilled a brand new 3/16" hole in the frame and sanded down the surround area to get a good contact. I have re-ran the ground wire for the alternator to the frame. I have also added a bypass wire from the voltage regulator box to the same location on the frame to help ground the voltage regulator.

This was all a fail and I still read 17.33 volts with the engine running.

Here is a link to the photo of the voltage regulator.

https://drive.google.com/open?id=0B14A3iwhYKHbUlRmWlpZNnJhVW8


A few questions:

1.0 - what is that thing big metal fuse looking thing?
2.0 - does the voltage regulator ground by contacting the voltage regulator metal box to fire wall?
3.0 - there is no wire going into the "I" pin? Am I missing a wire?

What else could I be missing?

 

[ymelnic1]

I checked the alternator and I don't have the red wire shown in the painless harness going from the battery to the solenoid as shown in the pic? Could this be an issue?

https://drive.google.com/open?id=0B14A3iwhYKHbT0xLTzNYN0VBdWc

 

[ymelnic1]

OK reconnected the ground wire from the alternator back to the regulator (was the correct setup) and ran another ground wire from the regulator metal case to the frame as an additional ground and got down to 14.9 volts while running. Better. I'm waiting on the new IVR for the cluster. Hopefully my issues are solved. Did not realize I was riding on a ticking time bomb. Thanks guys!

 

[DirtDonk]

I have discovered that my alternator was grounded via 14ga wire with the screw to the firewall that attaches the VR to the fire wall.

As you found, this is correct and similar to how the factory did it. Good catch by the way.

1.0 - what is that thing big metal fuse looking thing?

You mean the blasting cap?;D Just kidding. It's an original radio noise suppressor. Basically a condenser like in a points type distributor. Also called a capacitor when used in different applications, it's just there to reduce radio noise. As the name suggests.

2.0 - does the voltage regulator ground by contacting the voltage regulator metal box to fire wall?

Yep. Exactly.
And as you discovered, the typical method of creating the circumstances for proper charging, is to also run a ground wire (the factory is like 18-22 gauge, very small) directly from the alternator's case to the screw holding the regulator. This is, as I understand it, to make sure that both components carry the same ground potential. This lets everything talk to everything else so they know what's going on and how much charging current is needed all the time.
Probably was a good thing, given the Bronco's tendency to have poor grounding everywhere else.

3.0 - there is no wire going into the "I" pin? Am I missing a wire?

Nope. Ford had two distinct wiring schemes for the voltage regulators. All vehicles that ran with a charge indicator lamp on the dash used all four terminals of the regulator. And if I remember they were even swapped around, so that only the Orange "F" (for field) wire stayed on the same terminal.
All vehicles with ammeters (amp gauges) got the wiring that you're seeing on your Bronco.
F is Orange to the F terminal on the alternator.
S is Green w/red and gets 12v only when the key is in RUN. I believe this stands for "STATOR" on lamp-equipped vehicles, but I prefer to use the S for "switched" on our trucks with ammeters.
A is Yellow and has 12v all the time. This is the main sensing wire to tell the regulator how much voltage is in the system. A stands for Armature, but in our case I prefer to think of it as "always" because it's always-on.

Lots of mechanics wire Broncos and pickups with ammeters incorrectly because they only know how the cars and trucks with lamps were wired. This was by far the more common way, but back in our vintage there were still quite a few vehicles that used ammeters instead. So it's good to know both ways.

I checked the alternator and I don't have the red wire shown in the painless harness going from the battery to the solenoid as shown in the pic? Could this be an issue?

It depends. Do you have a Painless harness? Or is your wiring original?
And is your alternator a stock type, or upgraded more powerful alternator?

Paul

 

[DirtDonk]

OK reconnected the ground wire from the alternator back to the regulator (was the correct setup) and ran another ground wire from the regulator metal case to the frame as an additional ground and got down to 14.9 volts while running...

Great news! Glad it's down to earth a little more.
Still higher than most, but .4 volts is not that bad. And it could be just the variation in meters as well. Not enough to worry about at this point.
But now you know too that if you ever see a voltage reading on a Bronco that's more than 15.5 volts, it's time to start looking for the issue.
Some modern vehicles will put out as high as 16v under normal conditions. But most, if not all vintage vehicles like ours will be expecting no more than about 14.5 or so under normal conditions.

If you're using your ammeter still, they work well (when they work) and you should see a high "+" reading right after firing up the engine as the alternator tries to charge the battery back up. Then it will gradually come down from it's high point to a level just above zero.
If you turn things on without the engine running, or if your charging system is not doing it's job when the engine is running, your amp reading will go to negative "-" by varying amounts. Depends on the load.
You can see this just by turning on the key. The needle should flicker slightly to the negative, then go deeper still as you turn on things like headlights and heater blowers.

It's a cool gauge to have I think, but using a voltmeter along with it would be the ultimate.

Paul

 

[oleguy74]

I put in a new voltage regulator today. Got one at Auto Zone. I have discovered that my alternator was grounded via 14ga wire with the screw to the firewall that attaches the VR to the fire wall. I have drilled a brand new 3/16" hole in the frame and sanded down the surround area to get a good contact. I have re-ran the ground wire for the alternator to the frame. I have also added a bypass wire from the voltage regulator box to the same location on the frame to help ground the voltage regulator.

This was all a fail and I still read 17.33 volts with the engine running.

Here is a link to the photo of the voltage regulator.

https://drive.google.com/open?id=0B14A3iwhYKHbUlRmWlpZNnJhVW8


A few questions:

1.0 - what is that thing big metal fuse looking thing?
2.0 - does the voltage regulator ground by contacting the voltage regulator metal box to fire wall?
3.0 - there is no wire going into the "I" pin? Am I missing a wire?

What else could I be missing?

1.0 noise suppresser capacitor.
2.0 regulator grounds with a wire from alt(stock)
3.0 is for charge lite (alt lite)you don't need it.

 

[ymelnic1]

So I decided to run brand new 14 gauge ground wires (one from alternator one from frame) with new connectors to make sure to seal everything up properly once and for good. Aaaaaand I'm back to 17.6 vols. I even ran a ground wire from the metal case directly to the battery (-) to make sure it was properly grounded. Nothing... The only thing different that I can think of is that the wire from the alternator to the regulator is a heavier gauge than the stock...

I really don't get this thing.

 

[BoulderMike22]

I know it might not be the best thing to hear because it requires dropping the tank, but I recently had a similar issue (although mine would only move to just above empty with power on). I chased everything electrical on this list plus some. I also had a new sending unit and what it ended up being was the float on the sending unit had come off the post. It only clips in by a plastic clip. Yours could have come loose while the tank was full and so the ohms constantly read full now. Once I pulled the tank and recovered the float, I shaved a little off the plastic piece to get a better fit and I haven't had an issue since...


Sent from my iPhone using Tapatalk

 

[ymelnic1]

I have now tried to run the engine for a few minutes to see if there is a voltage drop. There is. After a few minutes, I watched the multimeter drop to 15.3. I decided to drain the battery overnight and try to start from a "reset". I'm thinking if the battery already was overcharged at 15.5 volts, maybe the regulator is trying to keep up with it? Again, I'm not at all an expert and may be over my head here, but I think it's worth a shot.

 

[DirtDonk]

Don't worry about the larger gauge wire in this case. The alternator is only supposed to put out as much as is required of it for the purpose of running the electrical component(s) and keeping the battery charged.
If your 130 amp alternator is only called on to produce 17 amps, then that's all it's going to put out.

At least that's the theory on how they're supposed to work.
At any time did you unbolt the regulator from the body while the battery was still connected and the regulator was still plugged in? If so, you may simply have burned up the new regulator.
I'm not sure if modern electronic VR's are susceptible to the same problems that the old ones were (probably are) but that's one of the things you're not supposed to do. You can plug in and unplug the connector even while the engine is running, but you're not supposed to have 12v to the regulator (supplied constantly through the Yellow wire) without the unit being grounded.

And just out of curiosity, why did you opt to redo things when it was working earlier? Were you just trying to clean things up? Or were the other wires just temporary?
We have a saying around here. "It's just temporary. Unless it works!";D

Good luck.

Paul

 

[ymelnic1]

Started her up this morning and the voltage at the battery is 14.20 volts. Also go the new IVR from Tom's. Put it in and my fuel gauge is spot on! Thank you guys for the help and support. This is why this forum is the best!

 

[garberz]

Started her up this morning and the voltage at the battery is 14.20 volts. Also go the new IVR from Tom's. Put it in and my fuel gauge is spot on! Thank you guys for the help and support. This is why this forum is the best!

Good news! Now you can move on to the next issue on the list.

Mark