S-100 gauges

My S-100 has been converted over to 12v by the previous owner, so I'm not sure if my gauges are stock. The gauges that are in it are green with the bull's eye in the center (first two attachments). I know on my R-series, the gauges are white with a red IH in the center (third attachment). I know that we have had a few grain trucks, a 68 and 74 I think, that had the 12v green bull's eye gauges. Did IH make the green gauges in 6v or are the ones in my truck already 12v? Also, if they are 6v, would it be easier to get 12v green gauges out of a newer truck since I'll probably redo the wiring harness anyways?

coakes00,
Yes, the guages with the green bullseye and two idiot lights did come in a 6V version. That's what my '56 S120 has in it and it's 6V positive ground. Some of the larger trucks that came from the factory with 12V had a power supply behind the guages to step the voltage down.

Here is a link to a thread about that- viewtopic.php?f=8&t=35&p=19278&hilit=guages#p19278

Dean

The early Loadstars had gauges that looked exactly like the ones in my S160. The S series has 6 volt gauges and the Loadstars are 12 volt. I thought an early Loadstar might be a good source for updating an older truck to 12 volt gauges. Or maybe just get the voltage limiter off the newer 12 volt gauges?

I spent a few hours in a salvage yard last week looking at nothing but IHC gauges. Yes, the green bullseye gauges were on the S series but also the Loadstars and, I think, some Cargostars and Transtars. What I did notice though is somewhere there was a change in the gauge set up. For the older gauge head you had 4 actual gauges. For the newer ones you had gauges for fuel and temp, but idiot lights for oil and generator. Although I didn't pull any of the newer gauge heads, all the ones with 4 actual gauges had the mechanical voltage reducer. The problem I ran into is none of the reducers worked, I think due to time and weather, so just going with a newer gauge head might still be hit and miss.

We've had a lot of discussion about pulsing senders and pulsing reducers, so I guess I might as well add my 2 cents worth. I've seen actual IH literature that says in the earlier KS gauges that used the heated bimetal strip they ran off of 5 volts. And I agree that with that kind of system you would have 5 volts and 0 volts (off and on, early digital). What varied was the distance between contacts on the bimetal strip of the sender. The closer the contacts were (contacts were closed longer), the closer the average voltage was to 5 volts, which gave you a higher deflection of the gauge. The further the contacts were (contacts were closed shorter) the closer the average voltage was to 0 volts.

However, I think the later KS gauges are designed completely differently using variable sender resistance to control gauge deflection. My thoughts are althought these gauges are designed for 6 volts and running off 12 volts, they really don't care what kind of step down device is used. They don't need a pulse, they just need the voltage in the range the gauge can handle. Prior to solid state that device was a mechanical bimetal step down as was seen on all the green bullseye gauges I looked at, but today it could just as easily be a constant voltage regulator. The question still in my mind is what was the step down voltage, 5, 6 or 7 volts (my bet was 6 volts)? I was going to test out my theory and add hard evidence to the OldIHC body of knowledge by making CVRs of each voltage and using with both systems and end the back and forth on what's our best solution. But unfortunately I couldn't find a functioning bimetal strip fuel sender, so my 15 minutes of fame and contribution down the drain. Possibly someone else with the working components and curiosity can perform the experiment.

Sorry, I hope I didn't hijack the thread.

Dilton

A fully-charged 6V battery should be capable of providing 6.9 volts, or 2.3 volts per cell x 3 cells. A fully charged 12V battery should also be capable of providing 2.3 volts per cell, or 13.8 volts.

Why do I bring this up?

Well, with those nominally 6V gauges, with a fully-charged new battery they'll be seeing almost 7 volts. I also know that not everyone back in the day kept their electrical system up to snuff, so a lot of those gauges probably saw a lot of days of 5V, and possibly less. So the knowledge of what voltage a 12V system "should" be stepped down to, in order to use the 6V gauges, eludes me. [Now, I also know that when it comes to modern computer-controlled engines, the standard for the throttle position sensor is 5 volts. But that means little to this discussion.]

Other than the ammeter, I don't think ANY of the L-R-S gauges actually had any numbers on them...so at best, they were, as Pappy once told me, "a fair guessing stick." So what level of accuracy SHOULD we expect from a gauge with no numbers? Your guess is likely as good as mine.

I am going with New Vintage Gauges.

John