Gauge testing
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Logistics Pro
Joined: Nov 2011
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From: Northville, MI
Gauge testing
I'm to the point of disassembling the dash and fixing wiring, switches, duct work, etc. I checked the Forum technical files but can't seem to find the answers that I need on how to test gauges and sending units. I have an ohm meter and actually have a box that you can dial in a particular resistance to simulate a sending unit but I need the sending unit ranges.
Also the ammeter is interesting as it looks like it just measures the magnetic current flow with no other connection to the system (see attached pictures). My question is does the wire from the main battery connection go through there and is there something else on the line that I am missing that goes in that holder? I would think that it would be the wire to the generator but I have converted to a modern one wire alternator.
Also the ammeter is interesting as it looks like it just measures the magnetic current flow with no other connection to the system (see attached pictures). My question is does the wire from the main battery connection go through there and is there something else on the line that I am missing that goes in that holder? I would think that it would be the wire to the generator but I have converted to a modern one wire alternator.
Fleet Owner
Joined: Jul 2004
Posts: 27,294
Likes: 1,055
From: NM
It isn't straight-forward testing the gauges, about all you can do is see if the coils inside are "open" circuits. They have bimetal strips with heater elements, just like the senders. They are adjustable tho. Look under the paper on the backs of the gauges. You'll see a small hole and a gear-looking wheel inside, that can be used to fine-tune the readings.
The ammeter is an inductive unit, no other connections. When using an alternator you want to have the alternator connection to the loads on one side of the loop on the ammeter, and the battery on the other. If you run the wire from the alternator thru the loop, you'll be seeing alternator output, not the "net" charge/discharge. That may actually be useful, because at least on mine, within a couple minutes of start-up it just reads Zero all the time (net).
Here's what an oil pressure sender looks like inside. Instead of being a variable resistor, the heating element causes the signal to pulse, so that the time-averaged voltage varies with oil pressure. Inside the gauges is somewhat similar.
The ammeter is an inductive unit, no other connections. When using an alternator you want to have the alternator connection to the loads on one side of the loop on the ammeter, and the battery on the other. If you run the wire from the alternator thru the loop, you'll be seeing alternator output, not the "net" charge/discharge. That may actually be useful, because at least on mine, within a couple minutes of start-up it just reads Zero all the time (net).
Here's what an oil pressure sender looks like inside. Instead of being a variable resistor, the heating element causes the signal to pulse, so that the time-averaged voltage varies with oil pressure. Inside the gauges is somewhat similar.
Junior User
Joined: Jan 2012
Posts: 80
Likes: 0
From: south carolina
Hi I need help have 1948f1 pu 6 4sp 6volt.Rebuilt starter generator new battery solinoid regulator.battery goes dead no matter how far you drive I noticed under dash 2 circuit breakers original would these be causing my trouble?How about ignition switch sometimes gauges dont move then shut off truck and restart gauges are fine,any help would be great thanks
Fleet Owner
Joined: Jul 2004
Posts: 27,294
Likes: 1,055
From: NM
Hi I need help have 1948f1 pu 6 4sp 6volt.Rebuilt starter generator new battery solinoid regulator.battery goes dead no matter how far you drive I noticed under dash 2 circuit breakers original would these be causing my trouble?How about ignition switch sometimes gauges dont move then shut off truck and restart gauges are fine,any help would be great thanks
Thread Starter
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Logistics Pro
Joined: Nov 2011
Posts: 4,685
Likes: 81
From: Northville, MI
It isn't straight-forward testing the gauges, about all you can do is see if the coils inside are "open" circuits. They have bimetal strips with heater elements, just like the senders. They are adjustable tho. Look under the paper on the backs of the gauges. You'll see a small hole and a gear-looking wheel inside, that can be used to fine-tune the readings.
The ammeter is an inductive unit, no other connections. When using an alternator you want to have the alternator connection to the loads on one side of the loop on the ammeter, and the battery on the other. If you run the wire from the alternator thru the loop, you'll be seeing alternator output, not the "net" charge/discharge. That may actually be useful, because at least on mine, within a couple minutes of start-up it just reads Zero all the time (net).
Here's what an oil pressure sender looks like inside. Instead of being a variable resistor, the heating element causes the signal to pulse, so that the time-averaged voltage varies with oil pressure. Inside the gauges is somewhat similar.
The ammeter is an inductive unit, no other connections. When using an alternator you want to have the alternator connection to the loads on one side of the loop on the ammeter, and the battery on the other. If you run the wire from the alternator thru the loop, you'll be seeing alternator output, not the "net" charge/discharge. That may actually be useful, because at least on mine, within a couple minutes of start-up it just reads Zero all the time (net).
Here's what an oil pressure sender looks like inside. Instead of being a variable resistor, the heating element causes the signal to pulse, so that the time-averaged voltage varies with oil pressure. Inside the gauges is somewhat similar.
On the ammeter should I loop the wire onetime around that hoop fastened to the back of the gauge? The attached picture is one I got here on this FTE and is very handy but it looks like the wire was cut so I can't tell if it was looped around or not. I have seen that on other applications.
Thanks
,
Fleet Owner
Joined: Jul 2004
Posts: 27,294
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From: NM
The ammeter wire just needs to pass thru the loop; I think if you wound it around it might cancel out the magnetic field? Or double it?
The fuel sender is the only one that is a pure resistance. Both the temp and oil senders are just like shown in the picture.
The fuel sender is the only one that is a pure resistance. Both the temp and oil senders are just like shown in the picture.
Junior User
Joined: Jan 2012
Posts: 80
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From: south carolina
gauge testing
THANKS FOR THE INFO.I WAS TOLD MY LITE SWITCH HAS A FUSE ON IT ITS A REPLACEMENT AND THEY SAID YOU CANT HAVE DOUBLE FUSES ON THE SAME CIRCUIT.IS THIS TRUE THIS 6V SYSTEM HAS A JUNCTION BOX AND WOULD THIS DRAIN MY BATTERY?ALSO I NOTICED MY POSITIVE CABLE IS GROUNDED TO THE HEAD .IM TOLD IT SHOULD BE GROUNDED TO CHASSIS BUT WHERE?CAN I GET A PICTURE OF ORIGINAL GROUND LOCATIONS FOR THIS VECHICLE THANKS
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Fleet Owner
Joined: Jul 2004
Posts: 27,294
Likes: 1,055
From: NM
THANKS FOR THE INFO.I WAS TOLD MY LITE SWITCH HAS A FUSE ON IT ITS A REPLACEMENT AND THEY SAID YOU CANT HAVE DOUBLE FUSES ON THE SAME CIRCUIT.IS THIS TRUE THIS 6V SYSTEM HAS A JUNCTION BOX AND WOULD THIS DRAIN MY BATTERY?ALSO I NOTICED MY POSITIVE CABLE IS GROUNDED TO THE HEAD .IM TOLD IT SHOULD BE GROUNDED TO CHASSIS BUT WHERE?CAN I GET A PICTURE OF ORIGINAL GROUND LOCATIONS FOR THIS VECHICLE THANKS
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Logistics Pro
Joined: Jun 2011
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From: u-rah-rah Wisconsin
THANKS FOR THE INFO.I WAS TOLD MY LITE SWITCH HAS A FUSE ON IT ITS A REPLACEMENT AND THEY SAID YOU CANT HAVE DOUBLE FUSES ON THE SAME CIRCUIT.IS THIS TRUE THIS 6V SYSTEM HAS A JUNCTION BOX AND WOULD THIS DRAIN MY BATTERY?ALSO I NOTICED MY POSITIVE CABLE IS GROUNDED TO THE HEAD .IM TOLD IT SHOULD BE GROUNDED TO CHASSIS BUT WHERE?CAN I GET A PICTURE OF ORIGINAL GROUND LOCATIONS FOR THIS VECHICLE THANKS
Oh, and the 6v positive ground was to the block from the factory.
If you don't have a '48-52 Shop Manual, it is invaluable and worth the 30 bucks.
DW
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Logistics Pro
Joined: Nov 2011
Posts: 4,685
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From: Northville, MI
I got the new gauge faces on yesterday. I painted the needles with fluorescent orange paint as they were badly faded. I found UV LEDs at PepBoys and they really made the needles pop at night. But as usual with most of their LEDs they are too fragile and I broke 2 of 3 of them trying to get their narrow 30 deg beam focused properly. I found some 90 deg flat LEDs at Oznium.com that mount with adhesive that should work better. Then I found on SuperBriteLED's website brighter, 180 deg LEDs to replace the #51 bulbs that were in the normal sockets. They were pretty cheap so I got some different colors (cool white, yellow and UV) to see which works best. They should be here later this week. I'll put up some night pictures when I get the IP done. Thanks to you the wiring should be much easier.
Thanks again,
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