Gas gauge help

[chevyboy55]

I'm sure this has been posted a gazillion times BUT, I got way too many returns when I searched gas gauge,So lets go for a gazillion & one. The gas gauge reads 3/4 full when it's full(better that way than the other way)How can I fix it? It's an aftermarket blazer tank.

[byrd]

easiest and cheapest thing to do would be to replace the resistor on the back of the fuel gauge.

[manimal]

If the resistor doesnt do it then take the sending unit out and clean the contacts on the reostat.You can use a FINE fingernail file to clean off the gunk that may have formed,then reassemble and try it out.Make sure that you spray off the contacts with carb cleaner or better yet use electrical contact cleaner.If thats not it then it could be that the arm that holds the float is bent.

[72armyswbtruck]

Float Arm is the culpret!!!!!!
Without breaking it, try and bend it until you get the correct reading

[Longhorn Man]

Originally Posted by 72armyswbtruck

Float Arm is the culpret!!!!!!
Without breaking it, try and bend it until you get the correct reading

This should read Float Arm MIGHT BE the culpret!!!!!!

[chevyboy55]

I thought I read something about ohms & what they should be or something like that.As far as gunk that's not it it's a brand new tank & float.Kinda hate to just start bending the arm & that not be it.

[byrd]

Originally Posted by chevyboy55

I thought I read something about ohms & what they should be or something like that.As far as gunk that's not it it's a brand new tank & float.Kinda hate to just start bending the arm & that not be it.

That is why I said to change the resistor on the gauge itself. I onl know of two sending units for the repop blazer tanks and they are rated at 30 ohm 63-66 and 90 ohm 67-72. You can use an ohmeter at the tank and try to see what the sending unit is putting out, but if it were mine I would try the resistor. I have a bunch of them here if you want a known good one for $8 shipped I would be more than happy to help you out on this. I would need a couple of dasy to get one tested and verified as I have been very ill this week.LMK...Randy

[crm318]

i had the same thing happen. it turned out to be the resistor. i went to fix-a-guage.com and i bought one of their resistors and installed real easy. it was only like 17 dollars with shipping.

[67ChevyRedneck]

I have the exact same problem (I JUST figured this out yesterday, it's the first time I've put a full tank in the truck) It went just a hair past 3/4 full, exactly as you stated your's does. I have an aftermarket blazer tank in a C-10. Without dropping the tank or removing the bed, I can not get to the sending unit, what does the resistor on the back of the gage look like? I might have to take mine apart this weekend!

When the gage is on E, the tank is empty! So that part is working correctly as I have run out of gas a couple times running the truck around the yard before it was completed. That leads me to believe this resistor is the culprit.

SO byrd, which resistor SHOULD go with a blazer tank? When I take mine apart, if it's different, I can assume that's what is wrong? I'm sure my tank is a 69-72 blazer.

[crm318]

the resistor looks like a little white rectangular piece. the fix-a-gauge piece is universal and works on all applications. i would look into that before you get into the tank.

[cdowns]

the first place to check is the range of motion of the float arm if it doesn't move thru the whole range of motion it's saupposed to a resistor will do you no good except giving you a false reading

[bad72c10]

I have a bunch of them here if you want a known good one for $8 shipped I would be more than happy to help you out on this.

Do you have enough to send one my way? If it's only $8 It's worth a shot on my '72, it's a stock tank, but won't give me a good reading. If you do, I'll probably send you a PM with my address and get yours to send you a check. Thanks, Justin

[byrd]

Originally Posted by bad72c10

Do you have enough to send one my way? If it's only $8 It's worth a shot on my '72, it's a stock tank, but won't give me a good reading. If you do, I'll probably send you a PM with my address and get yours to send you a check. Thanks, Justin

Sure just send me a PM to remind me

[byrd]

Originally Posted by 67ChevyRedneck

I have the exact same problem (I JUST figured this out yesterday, it's the first time I've put a full tank in the truck) It went just a hair past 3/4 full, exactly as you stated your's does. I have an aftermarket blazer tank in a C-10. Without dropping the tank or removing the bed, I can not get to the sending unit, what does the resistor on the back of the gage look like? I might have to take mine apart this weekend!

When the gage is on E, the tank is empty! So that part is working correctly as I have run out of gas a couple times running the truck around the yard before it was completed. That leads me to believe this resistor is the culprit.

SO byrd, which resistor SHOULD go with a blazer tank? When I take mine apart, if it's different, I can assume that's what is wrong? I'm sure my tank is a 69-72 blazer.

The resistor is the same for the 67-72 truck fuel gauges. The only difference is the repop blazer tank has two optional sending units (that I know of maybe more??)30 ohm and 90 ohm. Now I am positive that you have the right sending unit as you would not get past 1/3 tank or so if you had the wrong sending unit.You could have a dirty/bad connection across the resistor, you can easily just visually check that. If you have an ohmmeter here is a way to check the gauge and resistor using this guide I have posted and that should tell you where you should look. This should done with the ignition off to protect your meter,you do not want to apply power to your meter when it is in the ohms function as you run the risk of damaging it or blowing a fuse in the meter.

[67ChevyRedneck]

Shoot, so it's probably not the resistor then? At least it's not the wrong one...

Now that I think about it, I remember testing the float on the blazer tank and I could have sworn that it went to E and F when hooked to the gage.... so what the crap is going on?

[byrd]

Originally Posted by 67ChevyRedneck

Shoot, so it's probably not the resistor then? At least it's not the wrong one...

Now that I think about it, I remember testing the float on the blazer tank and I could have sworn that it went to E and F when hooked to the gage.... so what the crap is going on?

There is no difference in the resistors, just the sending units.
I would really lean more on it being the resistor as you have stated you tried out the sending unit and it worked fine then. I was just trying to suggest the easiest thing to trouble shoot first, as dropping the tank is quite a bit of work and guess I'm a little lazy. I would make sure it is electrically sound before moving onto the mechanical aspect of it. Just my .02.

Randy

[72GMCburban]

The truckandcarshop.com has the resistor new for $10, but u have to pay shipping. Take your multitester to the gas station and plug it into the brown wire and start filling up. If the sending unit is working then you should read 90 ohms full.

My question is what do u do when the unit is sending the right ohms and you have replaced the resistor and it still doesn't work? That is where I am now!
---Mike

[chevyboy55]

Originally Posted by 72GMCburban

The truckandcarshop.com has the resistor new for $10, but u have to pay shipping. Take your multitester to the gas station and plug it into the brown wire and start filling up. If the sending unit is working then you should read 90 ohms full.

My question is what do u do when the unit is sending the right ohms and you have replaced the resistor and it still doesn't work? That is where I am now!
---Mike

So let me make sure I understand this correctly.It will read 90 ohms when full.Will it have a different ohm reading if it's not full?The bed is off right now & I want to rule out a sending unit while it's still off.

[72GMCburban]

Yeah, it should be lower, plug in the red to the brown wire and the black to a good ground and you can watch it fill up by the ohms. I shouted"cool, i don't need to drop my tank" as strangers looked at me strangley.
This is unbelievable!! I just found info posted here in 2003. All these guys were having trouble with their guage pegged f or empty...the fix? It was the fuse! purple band was blocking the break. Unreal, it fixed mine!
---Mike