30 ohm or 90 ohm gas gauge - The 1947 - Present Chevrolet & GMC Truck Message Board Network

erock805 · 11-28-2010, 10:21 AM

Can you test this? Trying to sort out my gas gauge issue. I have from what i can tell a square (74 to 87) sub tank. (looked at pictures at the part store) A big one. struggling on getting them working together.

I have two gauges that I tried both read all full when hooked up. yes its heavily grounded.

msgross · 11-28-2010, 10:24 AM

I "think" 67 and newer are 90 ohm... 30 ohm for older trucks...

'63GENIII · 11-28-2010, 11:28 AM

Not sure if you have the sender out, but if you do you can put an ohmeter on it and run it through it's full range. At one end of the cycle, you will see either 30 or 90 ohms. Pretty easy to convert to 30 from 90 if needed.

erock805 · 11-29-2010, 08:37 AM

Like msgross said it seems to be a different ohm rating. I found one guy that put in the older resister on his new tank and that worked.

erock805 · 02-20-2011, 09:42 AM

found some info on adding a 50ohm potentiometer inline...headed to Radio shack when the open...would love for my gas gauge to actually work!

jimmillac · 02-22-2011, 03:58 PM

If you are trying to use an old guage that is looking for a 30 ohm sender, and have a tank with a 90 ohm sender, you will want to connect a 50 ohm resistor in parallel with the 90 ohm sender. That is, one end of the resistor will go to the same terminal as your gas guage wire, and the other end of the resistor will go to ground. You will want to get a 50 ohm resistor with a wattage rating of 3 watts or bigger. I would also recommend you mount it away from the fuel tank because it is going to get warm.

**TR65** · 02-22-2011, 09:53 PM

Check out this thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=413579

I run the resistor fix on my truck. Works OK. Just non linear as shown on the graph in the thread.

TR

11-28-2010, 10:21 AM	#1
erock805 Registered User Join Date: Apr 2007 Location: gilbert, az Posts: 392	30 ohm or 90 ohm gas gauge Can you test this? Trying to sort out my gas gauge issue. I have from what i can tell a square (74 to 87) sub tank. (looked at pictures at the part store) A big one. struggling on getting them working together. I have two gauges that I tried both read all full when hooked up. yes its heavily grounded. __________________ "Do what you want to the girl, but leave me alone!"

11-28-2010, 10:24 AM	#2
msgross Registered User Join Date: Jul 2006 Location: Central PA Posts: 12,201	Re: 30 ohm or 90 ohm gas gauge I "think" 67 and newer are 90 ohm... 30 ohm for older trucks... __________________ The Garage: 1968 K-10 SWB - "Project Money Pit" 1996 Z-71 - "huntin rig" 1969 C-10 LWB (SOLD) "Project flip that truck or else" 1993 Passport, F@rd 1-ton (SOLD)"Project Cousin Eddie" My Garage Build "The 1,000 footer"

11-28-2010, 11:28 AM	#3
'63GENIII Registered User Join Date: Sep 2008 Location: San Carlos, Ca. Posts: 3,048	Re: 30 ohm or 90 ohm gas gauge Not sure if you have the sender out, but if you do you can put an ohmeter on it and run it through it's full range. At one end of the cycle, you will see either 30 or 90 ohms. Pretty easy to convert to 30 from 90 if needed. __________________ Chris '63 k15 long step Vortec 7.4 - L29 Blackbear tune, Five 0 Motorsports injectors, Chris Straub Cam, NV4500, divorced 205 52" front and 63" rear spring swap D44 / 14bff - disc axles Milemarker 9K and 10.5K hydraulic winches 63" & B52 Spring Install http://67-72chevytrucks.com/vboard/s...ng+swap+thread NV4500 Reverse Build Thread http://67-72chevytrucks.com/vboard/s...=reverse+build L29 - 7.4 Vortec Build http://67-72chevytrucks.com/vboard/s...&highlight=L29

11-29-2010, 08:37 AM	#4
erock805 Registered User Join Date: Apr 2007 Location: gilbert, az Posts: 392	Re: 30 ohm or 90 ohm gas gauge Like msgross said it seems to be a different ohm rating. I found one guy that put in the older resister on his new tank and that worked. __________________ "Do what you want to the girl, but leave me alone!"

02-20-2011, 09:42 AM	#5
erock805 Registered User Join Date: Apr 2007 Location: gilbert, az Posts: 392	Re: 30 ohm or 90 ohm gas gauge found some info on adding a 50ohm potentiometer inline...headed to Radio shack when the open...would love for my gas gauge to actually work! __________________ "Do what you want to the girl, but leave me alone!"

02-22-2011, 03:58 PM	#6
jimmillac Registered User Join Date: Jan 2011 Location: Cheyenne Wyoming Posts: 16	Re: 30 ohm or 90 ohm gas gauge If you are trying to use an old guage that is looking for a 30 ohm sender, and have a tank with a 90 ohm sender, you will want to connect a 50 ohm resistor in parallel with the 90 ohm sender. That is, one end of the resistor will go to the same terminal as your gas guage wire, and the other end of the resistor will go to ground. You will want to get a 50 ohm resistor with a wattage rating of 3 watts or bigger. I would also recommend you mount it away from the fuel tank because it is going to get warm.

02-22-2011, 09:53 PM	#7
TR65 Senior Member Join Date: Nov 2007 Location: Greenville, SC Posts: 873	Re: 30 ohm or 90 ohm gas gauge Check out this thread. http://67-72chevytrucks.com/vboard/s...d.php?t=413579 I run the resistor fix on my truck. Works OK. Just non linear as shown on the graph in the thread. TR __________________ 1965 C10 SWB Fleet Two owner LS2 Swap Thread http://67-72chevytrucks.com/vboard/s...d.php?t=413880



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.