1970 Fury III Temp, Fuel, & Ammeter Gauges

[1970FuryConv]

Bench Test Gauges: FSM 8-84, after connecting the voltage regulator for the instrument cluster to a 12 V test battery and then grounding the cluster base to the battery, the factory shop manual states to use tester C – 3826 to simulate different input to the fuel and temperature gauges. I wanted to bench test my fuel, temperature, and ammeter gauges, but I have no such tester and the factory shop manual doesn’t give a way to bench test an ammeter. Since I have a spare set of gauges, I wanted to use the best of each. Does anybody know of a bench test for these 3 gauges that doesn’t require a specialized tester from Chrysler? Thanks

 

[Big_John]

To check the temperature and gas gauge, I bought a used decade box on eBay. Dial it to 10 ohms for full scale, mid is 23 and low is 74 ohms.

I think I paid $25 for mine. They pop up here and there and there's one that works for $10 plus shipping right now. Vintage Decade Resistance Box 1 to 10K Ohms –Tests Good - Made by Clarostat Mfg | eBay

You can duplicate it with resistors too.

 

[1970FuryConv]

Shoot! Bidding ended before I got a chance at it. If I find another, is it just a matter of adjusting the Tens knob to the correct ohm resistance?

 

[Big_John]

Shoot! Bidding ended before I got a chance at it. If I find another, is it just a matter of adjusting the Tens knob to the correct ohm resistance?

Yes, the one in my pic is set at 23 ohms.

 

[1970FuryConv]

Elenco K-37 Resistance Decade Box | eBay

Would something like this work?
Does a decade box provide power in addition to resistance? If not, would the Decade box need to be on the Ground side of a circuit with an auto battery and maybe an instrument panel voltage regulator on the positive side?

 

[Big_John]

One of these would work too.

https://smile.amazon.com/Elenco-RS-...9067436&sr=8-4&keywords=decade+resistance+box

It takes a little more math as you have to add up the resistance, but it works the same. Example: if you wanted 78 ohms, you would switch the 40,30,4,3,1 switches.

 

[Big_John]

Elenco K-37 Resistance Decade Box | eBay

Would something like this work?
Does a decade box provide power in addition to resistance? If not, would the Decade box need to be on the Ground side of a circuit with an auto battery and maybe an instrument panel voltage regulator on the positive side?

No power, just resistance. You would hook it to ground in place of the sender. Power to the voltage regulator or provide 5VDC some other way.

I think that one on eBay is a kit.

 

[1970FuryConv]

OK, that's what I expected. Thanks for the warning on the kit.

 

[1970FuryConv]

No power, just resistance. You would hook it to ground in place of the sender. Power to the voltage regulator or provide 5VDC some other way.

I think that one on eBay is a kit.

Hi Big John
I finally got my vintage Decade Box yesterday after ordering it on ebay
Below are the details on my tests of gages from my convertible, spare gages from a parted Sport Fury, (The > means Yielded. No equations involved.)
Thanks again for your help
Gage Test

· Old mustang battery, 6.11 volts. Pos to LS Inner spade of Inst Panel Voltage Limiter. Negative to black term of Decade Resistor box

· IP Voltage Limiter (IPVL): RS single spade is output to temp and gas gages. LS inner is ign input power. LS outer is connector to radio capacitor. Believe supposed to reduce input to 5 volts.

· Decade Resistor Box: tested with Fluke 78 ohmmeter @ 10, 23, & 74 ohms. Accurate to less than 1 ohm. Move Positive to ground terms of gas and temp gages as test each. Big John on FCBO: 10 ohms should correspond to full on gage, 23 ohms middle, 74 ohms low on gage

· Gas SF, 10 ohms > ¾ tank, 23 > 3/8, 74 > no reading, 50 ohms to move needle

· Temp SF, 10 ohms > 5/8 across gage dial, 23 > ¼, 74 ohms, needle barely moves from lowest point

· Conv Gas: 10 ohms > ¾ tank, 23 > over 3/8, 50 > 1/16, 74 > no movement

· Conv Temp: 10 ohms > less than half, 23 > ¼, 50 > slight movement, 74 > no movement
I'm going to use the temp gage from the Sport Fury and the Gas from the Convertible.

Works better with RS on 10 and LS on 0

Still need to hook up the yellow to IPVL input spade to get the gage to read

Forgot to take pic on gas gage reading, use temp