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73IH810

Bad oil press. gauge in a scout?

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Last weekend, I decided to tear into the gauges on my '73 Scout to see if I couldn't get them working better. I had issues with the ammeter being off in the discharge, the fuel gauge never going past 7/8 full, and the oil pressure gauge was giving weird readings. I removed the gauge clusters and found good wiring on the plugs going to the backs of them, as well as no loose pins on the back of the pods which I read is rare. The first picture gives you an idea of what I started with. I them cleaned up the circuits/contact points on the boards with an eraser as well as replaced the old nuts with brass washers, lock nuts, and nuts. The second picture is the back of the ammeter/fuel level gauges. On the oil press./coolant temp. gauges, I got a new voltage regulator from a Scout supplier and installed it in place of the original unit. The third picture is of this gauge cluster done. Before I install the gauges back into the truck, I install a new oil pressure sending unit into the block, this was a unit for a Scout so it should be the correct ohms. Re-installed everything today and started the truck. Fuel gauge finally went to full, ammeter was reading correctly, and temperature gauge was working as it had. The oil pressure came up to the halfway point upon start-up and stayed there for about 3 mins, which made me feel pretty good at that point. Then it dropped down to low... I know the oil pressure was at a constant 50PSI this entire time thanks to a mechanical gauge I have under the dash. The wire to the oil pressure sending unit did not look bad, and had a good connector on it. Is this a bad oil press. gauge? Thanks for any input.

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Do you mean the voltage regulator for the gauges. Been a real long time but seems they should regulate a pulsing voltage at about 5 volts. Don't quote me on the voltage but I know those gauge voltage regulators were always a pain and gave you all kind of weird readings on IH pickups and trucks.

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Pete, I meant to say the voltage regulator for the gauges. When I first hooked it up, I checked and had 5V coming out of the brown wire going to the one terminal on the right in the third picture. I have heard plenty of others say they just don't read right, which is why I installed a mechanical pressure gauge years back. It just seems odd that it worked and then dropped down to "low" like it lost its ground from the pressure switch. Might be time for me to redo the bulkhead connectors on this thing...

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I would plug in the original pressure sensor as a first item, just to know?

I would suspect a loose connection. <_<

You might try shorting the pressure wire to ground to see if the meter pegs. I would suggest a resistor but can't recommend a size. Those sensors are usually in the 50 to 500 ohm range I think? A 50 will likely do it, or just short it to gnd. By design they should tolerate it. Ifn ya don't already know it the sensors go lower resistance as the reading goes up. (More current to the meter.) For testing a cheap 1K potentiometer from Radio Shack etc (in place of the sender) will likely drive it anywhere you would want.

Does anybody have the actual spec on that regulator? My 75 S1700 has one and I'd like to know. That whole pulsing thing is kinda weird.

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Before I replaced the sender unit and updated the gauges, the oil press. gauge would give me give me a "low" reading at higher RPM's and then sometimes a "high" reading at idle. Which almost seems the opposite of how it should function. I am going to double check the wire/connector going to the sending unit and give grounding out that wire a try and see if the gauge reacts. Thanks for the info.

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Don't worry about it. Most Scouts show oil pressure like that. It states in the factory service manual that 10-15 psi is okay at high idle. ( I know I had a hard time believing that also.) Eason

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I was able to find the instrument voltage regulator information in the motor truck service manual. It says a pulsating constant voltage of 5 volts regardless of input voltage up to but no exceeding 16 volts on 12 volt systems. Also, there are two different types of regulators. Some gauges have a internal regulator and those gauges will have three terminals. Other gauges that use the external regulator (little rectangular box) will only have two terminal. Also, the regulator is normally grounded through one of the gauge or panel mounting screws. It has to be grounded to work properly.

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The new solid state voltage regulator I installed had a ground wire that I grounded to the dash. I would have figured that if it wasn't grounded, then none of the gauges would have worked. I'm starting to wonder if the new sending unit, that was probably made in China may have just ruptured its internal bladder after a few minutes at 50PSI.

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73 ohms equals empty on a known good gauge , 10 ohms equals full, instead of grounding sender wire

use a bulb style test light clip ground to sender wire and the point to ground it should read somewhere around 1/2

on gauge , I will expand on testing a little later when I am done in the shop :) I have a pretty neat decade resistance box to test

gauges and such, Gauges are adjustable on the round body trucks but have to be disassembled

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I decided to inspect the connection at the sending unit, found it to be a forked connector. Removed it, cut back some new conductor from the wire and installed a ringed connector. Reinstalled wire to sending unit and fired up the engine. No movement at gauge needle. Got underneath it again and saw some oil around the back of the sending unit where the housing is crimped, which sure wasn't there before. Pulled unit and going to get a replacement, pretty sure this one is a dud. I will update ya once I get a new one. Hopefully closer to fully functioning gauges. Thanks for the info on the ohms. If the new sending unit does not correct the issue, then I will be focusing on the gauge itself.

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This info pertains to the IH trucks that are either 6 volt or 12 volt having external constant voltage regulators or the regulator built into one of the gauges

, The regulator puts out various voltages ranging from 2-3 volts up to 9-10 volts , the voltage averages 5 volts and is temperature compensated

The input voltage to the regulator can be 6 volts up to 14 volts

To test the voltage regulator you need a known good gauge (fuel ,oil pressure, temperature, ) if they are electric gauges they are all internally the same

just differently marked face plates, and a handful of resistors 2 -10ohm 1- 50 ohm 1-3ohm and some jumper wires

If you take your dash loose be sure and keep the assembly grounded to the chassis with a jumper

Take the sender wire off of good gauge and replace with a jumper wire with a 10 ohm resistor in series to ground ,,turn key on, Gauge should go right

up to the highest marking on the gauge, Start the truck up rev the engine enough to get the charging system operating ,the gauge should stay steady on

the high mark (+- needle width) , If it checks out your regulator is good

Now that you have proved that your regulator is okay you can test your other gauges by replacing the sender wire with a jumper and 10 ohm resistor for highest

reading ,then add in series resistors to equal 73 ohms and your gauge will read on the lowest end of the scale ,

The sending units can be tested , with an ohm meter , to accurately test them they have to be removed , the fuel tank being the easiest just move the arm while testing,

the oil pressure sender can be hooked to regulated air pressure , the water temp sender can be submersed in a hot kettle ,etc, If all else fails check the green wire :ph34r:

They make a gauge tester which I believe is something similar to this device i acquired which is called a decade resistance box

Essentially a box with variable load piles in it and you just dial up the resistance you require , I picked up a spare voltage regulator

to power up the gauges and just click the settings from 10-73 ohms while testing :)

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I am finding a number of these old gauges not reading correctly ,but they still work , the older enclosed round gauges can be taken apart (not easy )

and recalibrated with their built in adjustments ,and also made into whatever gauge you need with different faceplates

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Do bad ones tend to read low?

For bad meters the movement spring probably isn't spry anymore, but you may also find the various resistors have aged out of spec.

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MD yes they seem to read low ,they also seem to get jumpy and stuck , part of the problems they have is age (of course)

and the dirt and dust buildup that somehow gets inside of them

Taking the round gauges apart is not super difficult just kinda ___itchy bending the rim back neatly enough to take apart and reassemble

I am trying some new tools etc , to help out , Any ideas on this would be mucho appreciated !!

After experiencing the prices $$$ of good used gauges with decent needles,bezels, faceplates etc, Figured I might as well learn how to fix em

and make whatever gauge I might need oil,fuel,or temperature out of spare pieces and parts

Hows your ignition replacement "modules " coming along??

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Testing now. Had some power supply noise stuff that had to be worked out.

Tried on couple of tractors and a Ford pickup. Perfect results so far. The truck idled better. Tractors work fine but they were 12v already so not a lot of difference. Other than points should last about forever.

Been testing with 6 v coils and no resistor. Makes great spark (25kv) but the Cub coil was running hotter than I would like. Too much dwell time with stock points timing. Was hoping to say could reuse the 6v coils but that may be a stretch.

I never liked opening those gauges <_< Fun the first couple of times. Could maybe make a can opener like device to slowly peel the lip.

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Well after installing a 2nd BWD "made in Mexico" sending unit and having intermittent loss of gauge while driving, I finally order a US made Standard Ignition unit online. Installed it and now have all gauges functioning. Thanks for all the gauge information guys, I will be using it on my next project vehicle.

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