Calibrating gas gauge to sending unit 1967

[Ken A.]

Re: Calibrating gas gauge to sending unit 1967

Why get personal? My information comes from GM blueprints for the sender revision and the E-85 issue was addressed by GM years ago when they revised the fuel system specs to eliminate the wire round resistor.

[Jimmy G.]

Re: Calibrating gas gauge to sending unit 1967

Go to Radio Shack and buy a precision 90 ohm resistor and a 45 ohm also Attach the 90 ohm resistor to the wires at the sending unit and the gage should read empty (if memory serve me correctly) With the 45 ohm resistor it should read half a tank. Short the two wires and it should read full. I have a AC Delco gas gage calibration unit and that is exactly what it is in reality ie 2 resistors and a short. If the gage reads way off at that point then the sending unit needs calibration, and by calibration I mean bending the lever to make it read correctly

[Larry M.]

Re: Calibrating gas gauge to sending unit 1967

Go to Radio Shack and buy a precision 90 ohm resistor and a 45 ohm also Attach the 90 ohm resistor to the wires at the sending unit and the gage should read empty (if memory serve me correctly) With the 45 ohm resistor it should read half a tank. Short the two wires and it should read full. I have a AC Delco gas gage calibration unit and that is exactly what it is in reality ie 2 resistors and a short. If the gage reads way off at that point then the sending unit needs calibration, and by calibration I mean bending the lever to make it read correctly

Jimmy:

Excellent post and info. I didn't think these GM "calibration kits" even existed, although a number of old automotive articles (non-internet) have talked about using the resistors.

However, you may need to get a second set of resistors to comply with the latest GM standards.

Larry

[Wayne M.]

Re: Calibrating gas gauge to sending unit 1967

Sender should read 0 to 110 ohms for gas gauge to read properly on a C-2. If not replace sender.

This one is in my late '65 -- no reason to believe it isn't factory. You can see the "90 OHMS" stamped on the rheostat.



c

[Ken A.]

Re: Calibrating gas gauge to sending unit 1967

It was revised in 66 to 110 ohms, but covers were never changed. Your strainer looks pretty bad.

[Al R.]

Re: Calibrating gas gauge to sending unit 1967

Hey Donald and Jimmy, thanks for the info. I did contact the rebuilder today and he asked that I check the ohm readings. If less than 90, he asked that I call him back and let him know and he would make it right. I'm going to try to check it out this Sunday. Will post what I find. Jim D. , I don't think it would be fair to name the restorer until I've given him a fair chance to correct the issue if indeed it is his. It could be the gauge or ? I just don't think it would be right to name him and his work until proven it is his issue. I'm sure the vast majority of others feel this way. I'm just trying to isolate the problem at this time and then give either the sender rebuilder or the gauge restorer or me,(if I've overlooked something) the opportunity to correct the issue. Then at that time, I will name the person and tell either how he stood behind his work or does not stand behind it.

[Dan S.]

Re: Calibrating gas gauge to sending unit 1967

I'm glad to see this post as I'm having the same problem after installing a rebuilt instrument cluster and a new sending unit. I assumed from other posts that the float needed to be adjusted so I'll be interested to see if there is another fix.

[Al R.]

Re: Calibrating gas gauge to sending unit 1967

I was not able to check on the gas gauge/sending unit this weekend. I got into some type of poison ivory/oak or something that has jumped all over me. Got to the Dr today for treatment and medicine. Hopefully, I'll be able to get on it this up coming weekend and post the results. The Radio Shack near me has gone under. I called over to the next town and they gone out also. May not be able to locate the 45 and 90 ohm resisters and have to do it the shorting out of wires way.

[Jim D.]

Re: Calibrating gas gauge to sending unit 1967

Sorry to hear of your "itchy" situation. Good luck with Radio Shack. There is a store very close to me and what they carry is a joke unless you want a cell phone. Even their on-line ordering is a joke. I'm surprised the whole damn co. hasn't gone under yet. Fortunately, I have a large electrical supply co. close that carries pretty much everything.

[Steve G.]

Re: Calibrating gas gauge to sending unit 1967

Wouldn't it be simplest to start with using a coat hanger through the filler and lift the float to the top of it's travel and see what it reads and where the float is when you get that reading. If the float is coming in contact with the top of the tank before it hits the stop on the sending unit you know an adjustment in the float arm is what's required.

Push it to the bottom and see where it is relative to the stop in the empty position. This will tell you where it will be reading on that day you run out of fuel on the way to the service station.

Steve

[Steve G.]

Re: Calibrating gas gauge to sending unit 1967

Use a sealed (waterproof) flashlight when looking into the tank and not a trouble light. We want to hear back from you, not about you.

Steve

[Joe R.]

Re: Calibrating gas gauge to sending unit 1967

I was not able to check on the gas gauge/sending unit this weekend. I got into some type of poison ivory/oak or something that has jumped all over me. Got to the Dr today for treatment and medicine. Hopefully, I'll be able to get on it this up coming weekend and post the results. The Radio Shack near me has gone under. I called over to the next town and they gone out also. May not be able to locate the 45 and 90 ohm resisters and have to do it the shorting out of wires way.

Al,

I would bet that Radio Shack won't have 45 or 90 Ohm 5 Watt or more resistors anyway. I did a quick search, here's a 90 Ohm resistor you could order online:

http://www.mouser.com/ProductDetail/Vishay-Dale/RH02590R00FC02/?qs=sGAEpiMZZMtTURnxoZnJAFIabCjCpYdjjQSozi8%252bbxY%3d

Here's a 45 Ohm 25 Watter:

http://www.mouser.com/ProductDetail/Vishay-Dale/RH02545R00FE02/?qs=sGAEpiMZZMtbXrIkmrvidDNaDpN5VXc5XgHQZutgyUY%3d

Good luck!
Joe

[Steve G.]

Re: Calibrating gas gauge to sending unit 1967

In thinking about this a little more I'm pretty sure that the op's problem is at the 0 end of the range, not the 90 (or 110) end. Grounding the sending unit wire (0 ohms) should move the gauge to full if I remember correctly. His problem is the gauge not reading full at a full tank.

Ground the sending unit wire. If the dashboard gauge moves to full the problem is the sending unit., most likely not reaching the end of it's travel where it finds the end of the windings.

At 90 (or 110) ohms it should read empty.
Steve

[Ray G.]

Re: Calibrating gas gauge to sending unit 1967

This one is in my late '65 -- no reason to believe it isn't factory. You can see the "90 OHMS" stamped on the rheostat.



c

Great picture Wayne.

[Al R.]

Re: Calibrating gas gauge to sending unit 1967

I will probably try the shorting of the wires 1st, and then use an ohm meter connected to the sending unit to check it. I'm hopefully assuming that if the float is pulled to the uppermost height, then it will read 0 ohms and if pushed down as far as it will go then it should read 90 ohms. Is this correct? Also, do I risk the chance of bending the float arm by pushing it down to the bottom of the tank with approx. 1/2 tank of fuel in it ?