Did the 12 volt light attached to neg. battery post and the other to the disconnected ground cable. The light is bright white so I got a pretty good short that showed up out of nowhere. Pulled fuses and determined the short is in the guages. Pull the fuse or disconnect the power to the guages and light goes completely out.

Also, if I just disconnect the Fuel sending unit the light dims to the point of almost being off. This would the resistance from the volt meter that should be there?

Before I go out and plop down $50+ on a instrument cluster voltage regulator and pray it is the answer, is there something else I need to check? Can the fuel sending unit be shorted? How do you test this? Any tricks I can use?etc. etc.

Thanks in advance for any suggestions.

 

What light are you talking about...headlight, instrument light, idiot light? Maybe one of your instrument panel lights has popped out and is sitting on your fuel gauge. What kind of truck? Year?

J!

 

OK, let me see if I have this right;
You made a 12V test light, disconnected your negative battery cable and hooked the light up in series between the cable and the battery right?
I'm guessing your battery has been going dead so you ar checking for a draw or drain on the battery.

Now by pulling fuses you have narrowed it down to the guage circuits. Can you give us a bit more info? What year truck? what kind of mods - stock or aftermarket gauges, etc.
I'm not quite sure how the cluster is wired but you mention the cluster voltage regulator so I'm guessing the cluster has one of 12V to 6V doo-dads on it, have you tried disconnecting that and see what happens?

Bobby

 

The truck is a 1950 F-1 mostly stock but with a 12 volt negative ground and a one wire altenator which appears to be working fine, new wiring, etc. I had the guages (Temp., Oil, Fuel and Volts) restored by United Speedometer in 02. All of the electrical worked fine for 5 years and then all of a sudden I have this drain and the battery has been going dead.

The hot guage wire goes from the fuse block to one prong of an instrument cluster voltage regulator (Napa Part IR-1, about $50). A wire from the second prong on the ICVR goes to all of the guages, presumably carrying 6 volts.

When I remove the Guage fuse or disconnect the gauge wire from the ICVR the test light (connected between the negative post on the battery to the disconnected negative ground cable) goes completely out, so I know the short is in the guage apperatus or something connected to it, like the sending units.

A clue might be that when I have the guages hooked up and just disconnect the fuel guage from the fuel sending unit the light goes from bright white to a very dull light.

So, could it be the fuel sending unit and is there a way to test this? Also, is the residual dim light a normal result of having a volt meter?

 

Another clue. I hooked up the battery and turned on the ignition. The fuel guage went to full (which is correct) but the guage itself got real hot!

 

Ahhh much clearer picture now.

Ok, so you are running a 12 volt neg ground and using a Vol-ta-drop type of reducer to power the gauges at their original 6 volts.

And because when you hook the test lamp up withthe ignition off it lights indication power flow. I fyo udon't have a radio with a clock on it (or some other constant power item) youhave a short to a Hot source. for the sake of clarity, lets use the words "HOT" for items that have power on them all the time (like the headlight switch and brake lights - things that only draw power when you turn on another switch) and "SWITCHED" for items that only come on when the ignition switch is turned on (like gauges that the ignition switch powers and use power as long as they are activated) It sounds like you have a cross circuit short - switched item now getting power from a hot source as well as it's switched source. But no matter. Let try something different to test.

Since, as I mentioned, you shouldn't have any power flow to the gauges with the ignition turned off, chances are that you have a wire or connection somewhere on your instrument cluster, that is touching a another wire or connection that has power that is HOT all the time. For example, the wire going from your gas gauge to your sending unit is touching a hot contact on the back of the ignition switch. After 5 years of vibration it has worn a hole in the insolation and is now shorted allowing power to flow from the hot source to the gauge and to ground all the time (what makes the battery go dead)

First, if your ICVR was bad, it would effect all the gauges not just one. So I think it's ok (unless you have the type that has one little ones on the back of each gauge and if that's the case, the gauge wouldn't do anything if it was bad).

But nonetheless, here is what I would do. Try isolating the area where the short may be in.

First hook your battery and all your wiring back up like it would normally be.
Turn the ignition switch OFF.
Hook one end of your test light to a good ground.
Then if you can, go behind your inst. panel and touch all the gauge posts. You shouldn't get any light-up. If you do, then that's the gauge that is shorted.
Remove both wires from that gauge and test each one individually for a light up. If you get it, trace that wire to the short.

The gauge gets hot because it has double the power flowing to it - one from its bona fide source and one from the short (at 12 volts). It gets dim when you disconnect the sending unit because you have elliminated the primary ground to the shorted gauge (and it sounds like its somewhere in th efuel gauge system).

Try this and if you can't find the short, or if something weird happens, come back and let us know what has happened and we can try to wittle it down from there!

Good luck,
Julie

PS One more thought! How is your AMP gauge hooked up? Is it just an induction loop type or does it have dedicated hook ups for wires to connect. And how are you running that wire? I also have a one wire alternator and I ran the single wire through the induction loop, the out tothe battery lug of the starter solenoid. I doubt that wire from your alternator is shorted considering the amp it's carrying - you'd have a lot more goin gon in that truck that just a light if it was shorted. But I'm wondering about other wires touching it or the connections if you have them. Just food for thought.

 

I think I've entered the Twilight Zone. I've been working on this [ptj1g84g03948t3 problem for so many hours I'm going crazy!!!!!

Hooked everything back together, ign. switch off. FYI, as I stated, the Gauge HOT wire comes directly from the fuse panel with a 15 amp breaker. It does not go through the ignition switch, never has and it worked fine for 5 years.

I got power to the IN prong on the ICVR as expected. Put the test light to the OUT prong on the ICVR and it blinks on and off, about every second or so. Same results when I touch the powered side of the fuel, temp and oil guage (as I would expect as it is series connection from the ICVR OUT). The power side of the VOLT meter (I don't have an amp meter) is constant hot as it is hooked up to the IN prong on the ICVR.

The sender side of the fuel guage blinks very weakly, the sender side of the temp and oil guage blink just like the power side does. The back panel or the back of the instruments do not seem to being carrying any power, at least for now.

I did turn on the ignition. Same results except the fuel gauge gave me a reading and the guage did not appear to get warm this time.

It's like chasing a gremlin and I'm just about exhausted.

 

Thanks for the additional info.
I'm guessing that the gauge fuse in your fuse block is powered by an ignition feed otherwise the gauges would be powered up with the key off.

I think the regular constant blinking of the test light when hooked to the ICVR is probably normal. My guess is that is how the ICVR works. To cut from 12V down to 6V for the gauges my guess is that its opening and closing the circuit through a bimetallic strip to "chop" the voltage from 12V to 6V, basically making and breking the circuit to give you an average 6 volts.

A typical fuel gauge and sending circuit get power through the gauge and out to the sending unit to ground. The sending unit is a variable resistor, the gauge reacts to the diffference. If you disconnect the sender (open circuit) the guage should either read completely at empty or full. If you short the wire from the gauge to the sender to ground then the guage ought to read in the opposite direction. (Off hand I can't remember if an open circuit is full or empty or vice versa but you should get a difference between the two).

Depending on your test light and what kind of accessories you have in your truck it may be normal for the light to stay on very dim even with no draw. As Julie said, any modern accesory that has any kind of memory will draw a constant bit of juice. Most cars built after roughly 1980 or so have this constant draw which can be up to 50 milliamps, plenty enough to dimly light a test light. Right now I wouldn't worry about the test light lighting dim. The bright light is your draw.

With everything hooked up normally and your test light in place you might try disconnecting the fuel sending unit and then the power input to the fuel gauge and wee what kind of results you get.

Good luck
Bobby

 

The Gauge wire from the fuse block is HOT with or without the ignition switch being on. I too have a concern about this setup but it worked just fine for 5 years and over 3k miles.

I like the idea that my ignition switch SHOULD control the fuse block Gauge circuit but maybe it isn't, thus causing the gremlins. But how would this have changed over time? Any idea how to test this?

I've tried everything, including disconnecting the fuel gauge sending unit and power feed. The test light is dimmer but fairly bright and the gauges no longer blink. Thus the twilight zone reference.

I'm telling you, I didn't have this much trouble redoing the entire electrical system when I did the frame off restoration!!!

Could it be the ICVR? Would it be worth rolling the dice and spending $50 to find out? If $50 would for sure fix everything I'd buy a new ICVR in a heartbeat. I've spent over 8 solid hours chasing this gremlin.

 

LOL...chasing gremlins is a pain

The gauge fuse SHOULD be controlled by the ignition switch. It would be easy enough to test. Turn the ignition off and check the fuse with your test light.
Perhaps it has always had the draw and your battery has been good enough where you never noticed it. Now, 5 years later, the battery has finally had enough. How often do you drive the truck normally? if you used to start it every day or two and now you only start it once a month or so, then maybe thats why you finally noticed it.

I thought you could buy those ICVR's at the local NAPA store for around $30. I think Ford used them on trucks up through the mid 60's so if they don't list one for your truck try a later model truck.

It seems to me that if the ICVR is giving you the pulsing light then its probably working (I'm kinda guessing here....in my last post I said that I wasn't sure how the ICVR worked and that I was guessing about it "chopping" the voltage by pulsing on and off).

Bobby

 

The Gauge wire from the fuse block is HOT with or without the ignition switch being on. I too have a concern about this setup but it worked just fine for 5 years and over 3k miles.

Ok well thats wrong right off the bat whether it worked for five years or not. What that means, if true is your gas gauge is working all the time and yes the battery will eventually go dead. All of your gauges need to be switched - turned off with the ignition when th ekey is turned off. How you do that, whether you power your gauges right off the ignition switch through the ICVR, or power it off the fuse block which is shut off with the ignition switch is really six of one half a dozen of another. Basically what youare tellin gus is that your gas gauge has been "ON" for five straight years. If that's the case then I'm surprised it took this long for something to cook.

I like the idea that my ignition switch SHOULD control the fuse block Gauge circuit but maybe it isn't, thus causing the gremlins. But how would this have changed over time? Any idea how to test this?

Just like computers, there's no gremlins. This circuitry is doing exactly what it's creator has told it to do. The only dynamic is th epossibility that a wire somewhere has finally chaffed to the point where its shorted out, or some part has burned up. You really need to have two fuse blocks or distribution points. One that is hot wired from either the battery lug on the starter solenoid or the battery post on the ignition switch (which comes from the battery lug on the starter solenoid). The second fus block needs to be run from the Ignition or Accessory post on the ignition switch so the things on it get turned off when the switch is turned off.

The fuse block that is hot should distribute power to: headlights, brake lights, courtesy lights, glove box light, cigarette lighter, horn, etc. Here is a diagram of my trucks hot bus, or fuse block set up:



The fuse block that turns on with the ignition switch, or switched [distribution] bus should carry things like gauges, ignition, heater, wipers, signal lights, radio, etc. here is a diagram of my switched bus, or fuse block set up.



I've tried everything, including disconnecting the fuel gauge sending unit and power feed. The test light is dimmer but fairly bright and the gauges no longer blink. Thus the twilight zone reference.

Ok so, forget about the test light for a minute. What you are telling us is that every thing worked the way it should today, right? The gas gauge turned on and didn't get hot, right?

I'm telling you, I didn't have this much trouble redoing the entire electrical system when I did the frame off restoration!!!

OK well......your guages are hot for five straight years if what you are telling us is correct

Could it be the ICVR? Would it be worth rolling the dice and spending $50 to find out? If $50 would for sure fix everything I'd buy a new ICVR in a heartbeat. I've spent over 8 solid hours chasing this gremlin.

It could be. But it could also be that your gauge has soldered itself into a blob of solid metal, or the gas gauge sending unit has done the same. It could be 20 things. But, the chances are still best that you have a bare wire in that gas gauge circuit, OR...or, a wire from another accessory that is shorting into the gas gauge circuit - because your problem is intermittent. So, you need to wire your gauges correctly then check for shorts with a meter with the ignition on and off.

J!

 

A little something I found on the net.......


IC voltage regulators are three-terminal devices that provide a constant DC output voltage that is independent of the input voltage, output load current, and temperature. There are three types of IC voltage regulators: IC linear voltage regulators, IC switching voltage regulators, and DC/DC converter chips. IC linear voltage regulators use an active pass element to reduce the input voltage to a regulated output voltage. By contrast, IC switching voltage regulators store energy in an inductor, transformer, or capacitor and then use this storage device to transfer energy from the input to the output in discrete packets over a low-resistance switch. DC/DC converter chips, a third type of IC voltage regulators, also provide a regulated DC voltage output from a different, unregulated input voltage. In addition, DC/DC converters are provide noise isolation regulate power buses. For each type of IC voltage regulator, the output voltage can be fixed or adjusted to a value within a specified range.

Performance specifications for IC voltage regulators include regulated output voltage, output current, dropout voltage, quiescent current, and operating temperature. The regulated output voltage (Volt) represents minimum and maximum amounts in continuous mode (DC). The output current (IOUT) is measured under specified conditions. Dropout voltage (VD) is the minimum voltage drop across the regulator that maintains output voltage regulation. IC voltage regulators that operate with small dropout voltages dissipate less internal power, but have relatively high efficiencies. Measured in amperes (A) during the idling state, the quiescent current never makes it to the load. Instead, it flows from the battery to power the regulator itself. The operating temperature is a full-required range.

I was just wondering if the blinking of the test light you were seeing had something to do with the dropout voltage. Don't let me complicate things, just stick with Julie and bobbytnm. They will get you fixed up.

 

Cool info. I'm not sure it applies here though. What might be confusing is the way we've been tlalking about the ICVR. I believe that we are using the acronym ICVR to stand for Instrument Cluster Voltage Regulator and not Integrated Circuit Voltage Regulator.

The original equipment gauge cluster voltage regulator is a relatively small item attached to the edge of the cluster, approx 1' long x 1/2" wide x approx 1/2" deep and I would be very suprised if it had an integrated circuit in it (remember these were used in the trucks from the lae 40's through the mid 60's)

Bobby

 

LOL! Well I WAS wondering about that! But I thought maybe you guys had added some cool modern stuff to the instrument cluster! I have yet to get to that part of the restore on my truck! OK, Never mind! LOL

 

LOL...don't worry about it, you supplied good info.

I tracked down this old thread on the Ford voltage regulators (including the NAPA Auto part number). It looks like they used them up into the 70's...wow

https://www.ford-trucks.com/forums/5...e-reducer.html

I'd go dig up the old cluster from my 49 and tear it open to see how it worked except that the last known whereabouts of my cluster was on the way to Australia...lol

Bobby