Floating gages
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Posting Guru
Joined: Jul 2010
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From: Marysville, WA
Put my spare orig IVR in, start the truck and warm it up to where the gages sit, mark em, swap to the new IVR and adjust it to make the gages read the marks. Then go fill the truck and make sure full is full and fine tune from there.
Unless someone has a better idea.....
Unless someone has a better idea.....
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Joined: Jul 2010
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From: Northeast, OK
That would work for fuel, but to get them all back would require pulling and reinstalling all three pins. I think I'd do what Don is planning - turn one pot and fix everything in one go.
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From: Denver Metro Area, CO
The electrically-heated gauges - those run by sending units on the vehicle (fuel level/oil press/water temp) - all look like so:
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From: Virginia
Reminds me of Dad's '72 Mustang Grande. Borrowed it when one of ours was down and drove it home thinking "that gauge is basically on empty, so I'll have to fill up tomorrow". It didn't start the next morning. Later he told me that it runs out when the needle touches the empty line. 
Personally, I wouldn't want the gauge to read that way as other vehicles don't work that way and no one will expect it. Like I didn't.
Personally, I wouldn't want the gauge to read that way as other vehicles don't work that way and no one will expect it. Like I didn't.
If you look at the sending units on most vehicles, the float arm will go down and hit a stop when the fuel level is low, and the pickup sock is always a couple of inches below where the float stops.
So the tip as it was told to me is to keep an eye on the needle as you get near empty and you stop and go around turns, the needle will rise a fall slightly because the fuel is sloshing around bouncing the float up and down. As the fuel gets even lower, you will find the needle will settle down and just sit there. That means the fuel is below the float level where it rests on the stop, and you usually have about 3 gallons more less depending on the vehicle and the fuel tank design. So if the needle is sitting there dead on empty, you had better find a station somewhere.
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Joined: Jul 2010
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From: Northeast, OK
Sorry I am creating another rabbit trail in this thread, but here's a tip someone told me that seems to work when you don't know where the vehicle runs out:
If you look at the sending units on most vehicles, the float arm will go down and hit a stop when the fuel level is low, and the pickup sock is always a couple of inches below where the float stops.
So the tip as it was told to me is to keep an eye on the needle as you get near empty and you stop and go around turns, the needle will rise a fall slightly because the fuel is sloshing around bouncing the float up and down. As the fuel gets even lower, you will find the needle will settle down and just sit there. That means the fuel is below the float level where it rests on the stop, and you usually have about 3 gallons more less depending on the vehicle and the fuel tank design. So if the needle is sitting there dead on empty, you had better find a station somewhere.
If you look at the sending units on most vehicles, the float arm will go down and hit a stop when the fuel level is low, and the pickup sock is always a couple of inches below where the float stops.
So the tip as it was told to me is to keep an eye on the needle as you get near empty and you stop and go around turns, the needle will rise a fall slightly because the fuel is sloshing around bouncing the float up and down. As the fuel gets even lower, you will find the needle will settle down and just sit there. That means the fuel is below the float level where it rests on the stop, and you usually have about 3 gallons more less depending on the vehicle and the fuel tank design. So if the needle is sitting there dead on empty, you had better find a station somewhere.
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From: Marysville, WA
And here we have the second attempt:
And here we have power:
The potentiometer is very sensitive, so I may try some other resistors to get it less sensitive and better tuneability. I have enough parts for 10 tries.....
If it stops raining, I may go put it in.
And here we have power:
The potentiometer is very sensitive, so I may try some other resistors to get it less sensitive and better tuneability. I have enough parts for 10 tries.....
If it stops raining, I may go put it in.
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From: Northeast, OK
But, if you can figure out what voltage you need, closely, then you can pull the pot and/or resistor and put in a pot that has little range so it is easy to tune.
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From: Marysville, WA
Parallel or series? I used a 1k pot in this one. Being a wiper style pot, it works but not very accurate/precise. Which is irrelevant when I don't even know what voltage I need.
I am guessing the gages need 5.2v or so. Maybe up to 5.5v. I found a chart that gives resistor values to get specific voltage outputs with the LM338T, but without knowing the needed voltage...
I could put this one in, adjust it to where the gages match the stock IVR, measure the voltage and build another with fixed value resistors....
And the more I think about it, the more inclined I am to swap out all the gages for Autometers. That or just put the stock IVR back in and live with it.
I am guessing the gages need 5.2v or so. Maybe up to 5.5v. I found a chart that gives resistor values to get specific voltage outputs with the LM338T, but without knowing the needed voltage...
I could put this one in, adjust it to where the gages match the stock IVR, measure the voltage and build another with fixed value resistors....
And the more I think about it, the more inclined I am to swap out all the gages for Autometers. That or just put the stock IVR back in and live with it.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Parallel or series? I used a 1k pot in this one. Being a wiper style pot, it works but not very accurate/precise. Which is irrelevant when I don't even know what voltage I need.
I am guessing the gages need 5.2v or so. Maybe up to 5.5v. I found a chart that gives resistor values to get specific voltage outputs with the LM338T, but without knowing the needed voltage...
I could put this one in, adjust it to where the gages match the stock IVR, measure the voltage and build another with fixed value resistors....
And the more I think about it, the more inclined I am to swap out all the gages for Autometers. That or just put the stock IVR back in and live with it.
I am guessing the gages need 5.2v or so. Maybe up to 5.5v. I found a chart that gives resistor values to get specific voltage outputs with the LM338T, but without knowing the needed voltage...
I could put this one in, adjust it to where the gages match the stock IVR, measure the voltage and build another with fixed value resistors....
And the more I think about it, the more inclined I am to swap out all the gages for Autometers. That or just put the stock IVR back in and live with it.
But, the idea of using fixed resistors, or using fixed resistors with a pot of very small value is a good one. Don't give up now, you are too close to quit. If not for you then for the rest of us.
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From: Marysville, WA
The reason I am questioning this is...
Drive the truck to the local Radio Shack for the last resistors, note the gages just before parking, come out and start her up and they sit different. Hmm. Driving to work all this last week the gages read consistent. All checks before were on dry days. Today it was raining. Don't know if that was the difference as the change was not much, only half a letter lower, but noticeable to me.
Might be the grounds. Could the wet change it? Do I need to seriously clean all my grounds before going any farther? Could the harness be getting wet?
Drive the truck to the local Radio Shack for the last resistors, note the gages just before parking, come out and start her up and they sit different. Hmm. Driving to work all this last week the gages read consistent. All checks before were on dry days. Today it was raining. Don't know if that was the difference as the change was not much, only half a letter lower, but noticeable to me.
Might be the grounds. Could the wet change it? Do I need to seriously clean all my grounds before going any farther? Could the harness be getting wet?
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Joined: Jul 2010
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From: Northeast, OK
If the engine/cab ground is bad it could make a difference when it gets wet. But, did you check the gauges after driving a bit? Did they go back up? I'm wondering if they cool off a bit while parked and take a while to get back to that point. Also, many gauges seem to have a bit of resistance in them and will come up a bit when rapped or shaken, so maybe driving with the vibration causes them to read higher?