Product review. Dorman 55818 fuel tank sending unit

[RockwoodMike]

I have both of my fuel tanks out and on one tank the sending unit is rusty dust..No rehab on it and the other is complete but the ohm reading on it is when it is full it will show a good reading but once it moves downward it goes to open..Replacement time for both..

The pictures show the product..Amazon..30 dollars delivered (I don't have Prime)..

It is universal and will fit just about any depth of tank..My tanks are 14 inches deep and that is what you use to set the new one up..2 lengths are adjusted..The body of the unit is set as shown in the instructions and then the length of the pivot float rod has a certain length..

Thus creating the full pivot action from bottom to top..

My dash instrument cluster is buried somewhere and I will get it out to hot wire it and see if it works properly before I install it..

Comes with a new rubber seal and screws..

[Eyez Open]

I will be watching this one, I've a 80 gallon tank and yet to find a tank sending unit that is calibrated to the tank and gauges.

[RockwoodMike]

yet to find a tank sending unit that is calibrated to the tank and gauges.

There is 2 parts of a calibrated fuel gauge system..The ohms on the sending unit read 35 at the full position..100 at mid level and 195 at empty..

The other part is the gauge itself..When 12 volts is applied to the cluster, there is a voltage limiter inside the fuel gauge that is suppose to cut the 12 volts down to about 7..and that limited 7 volts feed over to the water temp gauge and oil pressure gauge..

Volt meter to the 7 volt terminal is giving me a full 12 volts..Not suppose to do that!!

So I need to open the fuel gauge up and see what give with that..

Screen shots from the service manual shows the info needed to understand all of this..

[DaveVA78Chieftain]

Dodge fuel gauge specs
73-10 Ohm Fuel Sending Unit Ford and Mopar
Volts: 6-24 volts positive or negative ground.
73-Ohm = Empty Reading. 10-Ohm = Full Reading.

Summit Racing

Google

[RockwoodMike]

73-Ohm = Empty Reading. 10-Ohm = Full Reading

On my old sending unit, at full tank position, it reads 30 ohms..the problem with the unit is it goes to open circuit with the lowering of the float arm..

Just wondering where you got these numbers of yours

Oh never mind, it is from summit..

[DaveVA78Chieftain]

Its a standard that has been around for years

[DaveVA78Chieftain]

Also there is a troubleshooting article in the Members area

[RockwoodMike]

https://www.summitracing.com/parts/clp-vsu-f

Got to get this figured out..not putting the tank back in till it is right

[RockwoodMike]

Or here on Ebay

https://www.ebay.com/itm/253063320216?hash=item3aebbfd298:g:bnYAAOSwXUlgBu0A&amdata=enc%3AAQAIAAAA8CYNjmsaJ3%2BQTjkRf4SGQiT6Neq0Lw%2FqQgyHSzERsgDkXoJ2ds3KVKNcXJOrrZwubVhGG%2FTsNB6lir8T74igGCuhuvUBv%2F7a%2Bq4ym7OGEHPPbnaG3zB0OdzGRnbJgPqWMpDx6%2Fj0EjxwoL8fZRb2UTR576EYKiXL%2BJv9CsMbM46f8Sf0HoJg8zBz1UGgZMUEbiWKI078R3UQJ1W0QU3ZkKuGlCaOuBKr5y95SA220ZWNVvsDr4AtJohAwrbQE%2FUWpCfiFgZes%2FlL%2Fn2EhS74nqekabnpcyFRJTIT9SwlJEq7huGyK7GQkfmNe57cWl1UJQ%3D%3D%7Ctkp%3ABFBMquaVs7Ri

[RockwoodMike]

You try to figure out what the original owner did to all of this..The best I can figure, he was having troubles with the gauges and replaced the fuel sending unit with the wrong one and that made the gauge get messed up even more..So here I come along testing this sending unit, seeing 35 ohms at full..

Easy to find a sending unit and WRONG!!

So open wallet and throw more cash at this thing..The hole I am digging keeps getting deeper and the light at the top of the hole keeps getting dimmer..

I opened the dash and will look at the fuel gauge that has the volt drop in it and maybe I can fix it..

I just want to keep this as original as possible..Need to keep the speedo cluster..

But all of this can be replaced with programmable instruments..

[RockwoodMike]

I give up with this cluster..I will just start over and have modern gauges that are programmable..

https://www.ebay.com/itm/261697663603?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D20221115143056%26meid%3Dd8b58798cfa64a6ba7f7b5f40a41c707%26pid%3D101612%26rk%3D1%26rkt%3D1%26itm%3D261697663603%26pmt%3D1%26noa%3D1%26pg%3D4375194%26algv%3DRecentlyViewedItemsV2&_trksid=p4375194.c101612.m4236&_trkparms=parentrq%3Aa38ea32c1890a8cc463139aeffff17c6%7Cpageci%3A075bc106-2e57-11ee-94c1-b6c7687d164f%7Ciid%3A1%7Cvlpname%3Avlp_homepage

Here is a fuel gauge that is programmable and will work with the sending unit that I bought with the wrong ohm settings..

Just keep working on it..

This same seller has a oil pressure, volt gauge, water temp to go with the fuel gauge..Just make it all new..

[DaveVA78Chieftain]

Will pipe in a bit of info:

First, while not fuel gauge related, the Ammeter setup in that year model was a bad design.  The Alternator output is applied directly to the Ammeter which has a bad habit of burning out over time and leaving you stranded (MAD Ammeter Bypass). The original Ammeter had the "shunt" inside the Ammeter which is what burns out.  New style dash, RM and later series chassis with 3 round gauge clusters, changed the design such that a section of the alternator wire from alternator to starter relay actually functions as the shunt for the new style ammeter it reads as voltage drop (milliamps of current draw).  The MAD article eliminates the ammeter from the circuit and recommends adding voltmeter to monitor alternator output.  Note: Ammeters are actually voltmeters that are scaled to show amperage as a function of a voltage drop across a shunt.

As far as the instrument cluster voltage regulator.  The regulator itself is embedded inside the Fuel gauge and supplies reference voltage to both the Fuel gauge and Water Temp gauge.  On RM and later series chassis' the regulator is separate and mounted to the rear of the instrument panel. While 12VDC is applied to the fuel gauge (jumper strap from ammeter), the regulator reduces the voltage to around 7 volts. So, if the dark blue wire between the fuel gauge and Water temp gauge is 12vdc rather than approximately 7vdc then the the regulator is shorted out making both gauges work incorrectly.

[RockwoodMike]

Will pipe in a bit of info:

First, while not fuel gauge related, the Ammeter setup in that year model was a bad design.  The Alternator output is applied directly to the Ammeter which has a bad habit of burning out over time and leaving you stranded (MAD Ammeter Bypass). The original Ammeter had the "shunt" inside the Ammeter which is what burns out.  New style dash, RM and later series chassis with 3 round gauge clusters, changed the design such that a section of the alternator wire from alternator to starter relay actually functions as the shunt for the new style ammeter it reads as voltage drop (milliamps of current draw).  The MAD article eliminates the ammeter from the circuit and recommends adding voltmeter to monitor alternator output.  Note: Ammeters are actually voltmeters that are scaled to show amperage as a function of a voltage drop across a shunt.

As far as the instrument cluster voltage regulator.  The regulator itself is embedded inside the Fuel gauge and supplies reference voltage to both the Fuel gauge and Water Temp gauge.  On RM and later series chassis' the regulator is separate and mounted to the rear of the instrument panel. While 12VDC is applied to the fuel gauge (jumper strap from ammeter), the regulator reduces the voltage to around 7 volts. So, if the dark blue wire between the fuel gauge and Water temp gauge is 12vdc rather than approximately 7vdc then the the regulator is shorted out making both gauges work incorrectly.

Dave, you pretty much summed it all up..What was suppose to be 7 was 12 and what was suppose to be the ohms range was wrong..

So I put all the cluster parts in a box and I will create a new cluster using new gauges with a volt gauge to replace the amp gauge..

I tried to open the fuel gauge and it just is not serviceable..and it looked burnt inside..

What I like about the fuel gauge linked above, it can be used on a variety of ohm ranges..And the sending unit that I was trying to create a review on will be able to be used..No loss on that!!

[BigAlsVehicleEmporium]

I will be watching this one, I've a 80 gallon tank and yet to find a tank sending unit that is calibrated to the tank and gauges.

Eyez Open,

The ohms range on this Dorman unit is 240 ohms empty and 33 ohms full. That range is used mostly for after market gauge. If this is for your auxiliary tank and you have a separate gauge for it that isn't a Chevy gauge, it's definitely possible that this is the one you would need. If both tanks display on the same gauge and that gauge shows the level of whichever tank you are switched to, then you might need a 0 ohms empty, 90 ohms full sender like was used on most 1965 and up Chevys.

I like the universal units that Tanks Inc sells and you can buy them in any of the common ohms ranges. Their TAN-GML model might be the one you need. If you're not sure, you could buy a few resistors to check if your gauge uses the range you think before buying a sender. If you've got any questions about trying that out let me know!

I used there TAN-ORG model for my Dodge gauges and it worked out great!

[RockwoodMike]

The ohms range on this Dorman unit is 240 ohms empty and 33 ohms full. That range is used mostly for after market gauge

And this is where I screwed up trying to fix the original dash fuel gauge..The dash had a after market gauge cut into it..And the best I can figure, it was to replace the stock gauge that went bad after loosing the cut down voltage built into it..

So here I am trying to replace the sender found in the tank when I pulled it out..Was able to ohm read the full position at 30 ohms..
Bought this Dorman and tried to bench test the stock gauge..Wasn't working right..Got out the service manual and it stated the 7 volt that should be the reference voltage..

Then Dave comes to the thread and tells me the ohms were wrong on the Dorman..Never knew that there was so many different configurations..

What a learning curve..

I will create a new dash with new gauges and go from there..

[Eyez Open]

I will be watching this one, I've a 80 gallon tank and yet to find a tank sending unit that is calibrated to the tank and gauges.

Eyez Open,

The ohms range on this Dorman unit is 240 ohms empty and 33 ohms full. That range is used mostly for after market gauge. If this is for your auxiliary tank and you have a separate gauge for it that isn't a Chevy gauge, it's definitely possible that this is the one you would need. If both tanks display on the same gauge and that gauge shows the level of whichever tank you are switched to, then you might need a 0 ohms empty, 90 ohms full sender like was used on most 1965 and up Chevys.

I like the universal units that Tanks Inc sells and you can buy them in any of the common ohms ranges. Their TAN-GML model might be the one you need. If you're not sure, you could buy a few resistors to check if your gauge uses the range you think before buying a sender. If you've got any questions about trying that out let me know!

I used there TAN-ORG model for my Dodge gauges and it worked out great!

Great link I Thank you for the effort. Actually it is a very user friendly, 0/90 ohm sender seems to be correct. Perhaps the time has come, I finally have my new door in and curtains to boot. This week I think I will just breathe.