The Stovebolt Site Forums The Shop Area The Electrical Bay FUEL GAGE/SENDER COMPATABILITY

I HAVE INSTALLED A 76 BLAZER GAS TANK IN MY 57 CHEVY STEPSIDE AND NEED TO KNOW IF THERE IS A WAY TO ADAPT MY EXISTING GAGE (30 OHM) WITH THE 76 SENDER(90 OHM)BY ADDING A RESISTOR OR ???.
ANY HELP WILL BE APPRECIATED AS I WOULD LIKE TO KEEP THE EXISTING GAGES.

Hey, welcome to the 'bolt!! Interesting question. I don't see how that could be done but what about adapting a 30 ohm sender to the new tank?

I would try the resistor. A 1/8th watt or a 1/4 watt should. The bands would be blue, black, brown. The 4th band is not too important thought a gold fourth band is 5% tolerance. Radio Shack sells some with 1% tolerance which is best. Other wise an aftermarket may work instead of the stock one. H. Started fixing cars and such over 40 years ago and I'm also an electronic tech. I hope this helps you out.

Henry; Please refresh my ol' memory here. Is that a 200 ohm resistor or (?), and where would he put it in the circuit?

600 ohm! Will this setup work when the circuit it is installed in is varying in resistance itself?

Stuart

Well, we're talking fuel guages here not temp. guages but I'm still wondering how this would work (using a 600 ohm resistor somewhere to compensate the difference between a 90 ohm sender and the original 30 ohm sender) I'd love for someone to explain this to me. Not trying to be a smarta$$ here, just want to learn.

Me too....I'll be hiding in the corner!


Stuart

GREAT THANKS GUYS!

IF ANYONE ELSE HAS AN IDEA I'M STILL OPEN.

I'LL DO THE TRIAL AND ERROR SYSTEM AS SOON AS THE SNOW MELTS AND I CAN GET TO MY OLD GAS TANK AND SENDER.
RICH 57

I don't visit this section of the forum very often but with little to do, I took a peek. I noticed some guys having a problem with this little formula question. For "Rich57" there is some good news and bad news...
The GOOD...
R1 x R2 90 x 45 4050
Rt= over Rt= over Rt=over Rt=30ohms
R1 + R2 90 + 45 135

so:Rt is the valve you need the sensor to be.
:R1 is the value the sensor is now.
:R2 is the value (45 ohm)you need to put in PARALLEL with the sensor.

The BAD...
"Waldo53" is right, A new sensor is the right way to go if you want it to read correctly all the time.
Your gauge linearity is out the window. It will only be correct for two readings, empty and full. For an example...1/2 a tank would be 45 ohms on your 90 ohm sensor. If you plug that number in above you get 22.5 ohms or about 1/3 tank showing.
A couple of other things...45 ohms is not a standard resistor but 47 ohms is and that will be ok. On temp. sensors the game is a little different in my option. The only linear portion of the temp. curve I worry about is 180 to 220 degrees. So you can "pad" an electric sensor to be linear in this portion of it temp. curve. I don't worry if the water temp. is a 125 degrees and the gauge is showing 140. I only worry about the range noted above.
Hope this helps.

The UGLY...

The forumla in my other post didn't get through. I guess this forum doesn't support that sort of thing so here it is again in a different way.
Rt= R1 x R2 divided by R1 + R2.
The valves for the different R's are in my other post. Sorry for the possible confusion

Or you can use the reciprocal of the sums of the reciprocals of all resistance values in the parallel circuit.

I'm going to be like Atomarc listening to others(hiding in the corner) hoping to learn something.

My first problem is I don't understand electronics lingo, so I hope there is a layman's explanation for me.

Like RICH 57, my gauage and sender are different. Only in reverse. I'm told Old sender is 30 ohm and Brand New gauge is 90 ohm.

Just wanted you guys to know your knowledge is important to other "listeners".

"Baldy" is correct also, the reciprocal method is also a way to solve for Rt. I find the above method easier than the reciprocal method when soloving for just two rersistors in parallel But the problem is, we were not solving for Rt. We are solving for Rx. I left that out thinking solving for an unknown (Rx) with algerba for guys who don't use it everyday would be trying. Maybe I should have pointed them in the direction of a "parallel resistance nomograph".

Thanx for the info. I installed new Dolphin gauges in my truck, but the fuel gauge didn't work. Finally changed the sending unit out with the one that came with the gauges and it worked fine. Now I know why!

beltfed; That's the way I saw it too. The guage would only be accurate at empty or full, anything in between would be way off. I still think the best solution is adapting a 30 ohm sender to the new tank. Good thread!

THANKS A BUNCH GUYS, I'M DISAPOINTED BUT AT LEAST I WON'T SPEND DAYS TRYING TO FIGURE OUT WHY THE GAGE DOESN'T READ RIGHT.

RICH 57