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Discussion Starter #21
As for that jumper I attached a female spade connector on one end and a male on the other. Jumper is about 3 inches long and the ends are crimped on good. With it hooked up like that I was able to touch the male spade on the gauge with my meter probe when I had the jumper on it and it shows 12v.

Next I removed both wires from the sending unit and attached my ohmmeter. Red to sending terminal and black to ground post. Shows 25 ohms. Tank should be full. I filled it until it wanted to come back out on me. Then drove only 5 miles home. I might be getting 25 ohms instead of 30 because back end is jacked up pretty high so I can get under there??

I also noticed that I was not getting a good ohms reading when I touched the black probe to the frame. It's all been thoroughly cleaned and undercoated. I was able to get a good reading at some places such as the little bracket that holds the union of the brake lines. So I made a short jumper with 3/8 inch circle connectors and ran that from the brake bracket to the screw that attaches the ground wire to the gas tank bracket. Then I got back under the dash and connected ohmmeter to brown wire and to ground and it shows 25 ohms so I'm confident I'm getting a good connection from gauge to sending unit to ground.

I suppose I could siphon out 4 gallons to see if ohms drops to 18 or 19??

I guess I'll pull the gauge out next and clean it like suggested.
 

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Discussion Starter #22
6. Disconnect the parts, very carefully, clean with copper brush. Clean very sensitive parts with only a small amount of spray cleaner. (I used electrical spray cleaner)
Where do I buy a copper brush and electrical spray cleaner?
 

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Discussion Starter #24
And now for a question on removing the gauge. The shop manual says loosen and lower the mast jacket from dash panel (See Steering, section 9, for complete procedure for lowering the mast). Do I have to do all that section 9 lists to remove the mast? All I really need to do is remove the clamp holding to the dash panel and let it swing down a little, right?
 

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Discussion Starter #25
Found out I was wrong about having filled the tank completely. I put in about 3 more gallons from a small can. It is definitely full now. Ohms reads 30.9 so 25 ohms with 13 gallons was right. I also took volt reading on the sending wire post and it shows .5 volts. I assume that's about right?

I got the gauge out. Here are some pics. Also a pic of brushes and electrical cleaner I bought. How do I go about cleaning it?
Gauge (1).JPG
Gauge (2).JPG
Gauge (3).JPG
Gauge (4).JPG
Cleaning stuff.JPG
 

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That is exactly what mine looks like.
  1. My approach was anything that looks breakable - I sprayed just enough (yeah, what is 'just enough' - till it looks cleaner i guess)
  2. I gently moved the needle mechanism and sprayed.
  3. I removed the backplate and wire brushed contacts, nuts posts on both sides most till the copper was clear or no old residue remained.
  4. Good Luck!
here is a picture!
FuelGuage.JPG
 

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Winch said: "Found out I was wrong about having filled the tank completely. I put in about 3 more gallons from a small can. It is definitely full now. Ohms reads 30.9 so 25 ohms with 13 gallons was right. I also took volt reading on the sending wire post and it shows .5 volts. I assume that's about right?"

Where did you measure the 30.9 Ohms? At the Fuel Sender across/between the Fuel Tank's Sender wire and ground wires? If so, yes. You're Sender is good.

How did you measure the .5Vdc at the gauge? Between which two points? And what was setting on your Voltmenter? Should have been "Volts DC" and "20" Volts range. (Always set your meter to a range value above what you expect to see). If not, try again using those settings. Doesn't matter which colour meter wire goes where.
Where I've never measured the value of the Sender lead, we'd need Custom Jim to jump in here to validate your method and reading.

Like Mburnette6 says.....go REAL EASY on that gauge with those brushes where any wires are located but lay into the spade connectors to get 'em good.
 

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Discussion Starter #28
Where did you measure the 30.9 Ohms? At the Fuel Sender across/between the Fuel Tank's Sender wire and ground wires? If so, yes. You're Sender is good.

How did you measure the .5Vdc at the gauge? Between which two points? And what was setting on your Voltmenter?
I stuck the ohmmeter red probe into the brown wire plug removed from the gauge and then touched black probe against metal of dash underneath. Yesterday I also tested ohms by touching probes directly to posts on the sender but I got the exact same readings as testing under the dash. By testing at the gauge I think it confirms a good circuit all the way back and a good ground return.

I measured voltage coming out of gauge by touching sender wire spade with red probe and touching a ground under dash. I did have voltmeter set to 20 on DCV. I just did that to see what it shows. I thought if zero then maybe that would indicate a problem inside the gauge.
 

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Discussion Starter #29
Well no luck. I cleaned it as good as I could following your instructions. It just doesn't respond at all.

Does anybody repair these things? I'm not going to spend what I see for a repro ($250 - $400)! I think I'll get back to making a 68 console with a 4 gauge pod work. I was going to plug the 4th hole with a clock but now I'll put a matching Autometer Phantom fuel gauge in there.
 

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Sorry to hear that. But, now you know how to do it. If you ask Dave at [email protected] he might have a used fuel gauge. I bought a bunch of $hit from him. Or you might have to buy the cluster. I don't know, but there is also no guaranteeing the one bought will work either.
 

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Discussion Starter #33
I would like to do a bench test so I need resistors in 7.5, 15, 22.5 and 30 ohms. I can order online from Allied Electronics and Automation. But I'm not sure of what to buy. Here is a description of some. Is this what I need?

CW005 Series Axial Wirewound Resistor 7.5Ohms +/-5% 6.5W +/-50ppm/degC

Resistor, Metal Film,15 Ohms,0.125 W,+/-1%,350 V,Axial,100 ppm/C,450 VAC,1.50"

Resistor; Wirewound; Res 22 Ohms; Pwr-Rtg 5 W; Tol 5%; Axial; Bulk

Resistor; Wirewound; Res 30 Ohms; Pwr-Rtg 3 W; Tol 5%; Axial; Bulk
 

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Discussion Starter #34
I would like to do a bench test so I need resistors in 7.5, 15, 22.5 and 30 ohms. I can order online from Allied Electronics and Automation. But I'm not sure of what to buy. Here is a description of some. Is this what I need?

CW005 Series Axial Wirewound Resistor 7.5Ohms +/-5% 6.5W +/-50ppm/degC

Resistor, Metal Film,15 Ohms,0.125 W,+/-1%,350 V,Axial,100 ppm/C,450 VAC,1.50"

Resistor; Wirewound; Res 22 Ohms; Pwr-Rtg 5 W; Tol 5%; Axial; Bulk

Resistor; Wirewound; Res 30 Ohms; Pwr-Rtg 3 W; Tol 5%; Axial; Bulk
 

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Discussion Starter #35
I'm holding off placing an order for those resistors until I hear from one of you guys who would know if they are what I need. I'd appreciate the feedback.
 

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Well, I only know a little but in an effort to bump this along for you......
I'm not familiar with the 'wire wound' type of resistors except for the old ballast type used on Dodges in the late 60's early 70's. But for a test-only application as you're doing, they should work. Expensive though, I would think.

I'm surprised you're not finding the 'ceramic' style resistors. They're pennies a bushel relatively speaking.
I take it there's no electronic component supply stores near you?
 

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Discussion Starter #37
Radio Shack is gone. An internet search didn't come up with any. I think I saw ceramic type resistors. I just didn't know what I was looking for. I'll replace the wire wound ones with ceramic.
 

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You just need the real basic low wattage resistors.

In my video showing how to test the fuel gauge system on my 68:


Pause the video at 3:29 and you will see the resistor in my meter down below with the yellow arrow pointing at it. The resistor is that round tubular thing with the Gold ring, Black ring, Blue ring, and the Brown ring. These rings starting in the opposite manner are a code that allows you to know what the value of the resistor is and the last band (gold in this case) refers to the tolerance which depending on the color ring can be plus or minus 5% or plus or minus 10%.

Test Resistor (1).jpg


You DO NOT need the higher wattage white clay type of resistors.

I normally don't buy resistors as I have them at work but they are not that expensive. The clay ones and the ones that can handle high wattage ARE expensive.

Jim
 

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Here is a shot of my meter when I was checking a particular value of a resistor. I've never committed the resistor code to memory and it's easier for me just to measure it with a meter. Just for the picture I took off the test leads on the meter and had the resistor going into the proper two holes to take the measurement.
IMG_8894.JPG


IMG_8895.JPG


When I was testing my 68 gauge which is a 0-90 ohm system, I unplugged the sending unit wire connector in the trunk and on the side going forward towards the gauge clipped the one end of the red alligator clip test wire to that terminal in the plug and the other end to one end of my test resistor. On the other end of the test resistor I clipped on the yellow test wire and the other end clipped to the trunk lid catch for a ground.

IMG_8896 Identified Parts.jpg



Jim
 

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Discussion Starter #40
That would be a good way to test a gauge still in the dash. I have a used one coming so I will rig up a test platform similar so that I can test it before putting the cluster back in the dash.

Just curious, how exact are the resistors? If you measure a 15.7 do you actually get 15.7?
 
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