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Discussion Starter · #1 ·
was working fine until i pulled the dash a while back to do some major detailing and fixing radio, bulbs, switches, etc. everything i fixed is still fixed but the one thing that did work, but now doesnt,is the gas gage,which is pegged below empty. the sending unit is new, i checked the ground back there and it is good, pulled off the dash pad today, removed and reconnected the plug connection to the gage, changed the gage fuse, now what? i'm counting on you John, you 'da man.
 

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Discussion Starter · #3 ·
dang. it looks like the electric gods are frowning on me lately. took the VOM out of the cabinet and it didnt work. changed batteries, changed fuses, nothing. looks like its time for a new one. i will pick one up tomorrow and try and get a reading on that pink wire. any suggestions on a VOM brand to buy? (the one that just crapped out on me was a craftsman. but to be fair it WAS several years old.)
 

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This has been discussed before but my opinion is I use cheap ones around the car. If I drop them I don't worry much.
 

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Discussion Starter · #5 ·
okay, this is tricky because i am trying to do this without removing the gage cluster, but reaching over the top of the dash(using a pen light and mirror) i got the probe into the top of the plug on the pink wire. when i turn the key to "on" and touch the other probe to the metal frame of the dash i am reading 12 volts on the meter. [BTW after buying a new Fluke meter today, i go home, turn on the craftsman once more before i toss it, and guess what? yep it fired right up this time. go figure.]
 

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Did you measure the 12 volts between the pink wire and the black wire? If that's there disconnect the tan wire. May be easier from under the car. The gage then should read super full.
 

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Discussion Starter · #7 ·
its very difficult to try and get both probes back there and see what you are doing for sure. i could not get any voltage when i thought i had them in place. i was pretty sure i could get on the black wire and did a continuity check to ground and did not get a beep.
 

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Can you pull up the connector slightly and get a clip lead on black's terminal and tie it to ground?
 

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Discussion Starter · #9 ·
i will try that tomorrow nite. i may have to pull the dash loose to get some room to work back there. the dang defroster vent is right over that gage. in any case i will give it a try and let you know thanks for your help.
 

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Discussion Starter · #10 ·
hmmm. i loosened the dash just a bit, have just a little better access to the connector for the fuel gage. removed the connector and tested it at the plug. i definetley have 12 volts at pink and i do have ground at black. i suspect that when the plug was installed it may NOT have been engaging the ground. it is not possible to see this unless i completely drop the dash which i am trying to avoid if possible. i tried numerous times to "feel" the plug onto the gage but i just cant see where it is going in relation to all three contacts. tomorrow i will rig up three jump wires with alligator clips, remove the connector and jump between the gage and the plug. if the gage works when i do this then i will know that the problem is that i am missing the male ground when i slip the plug on, right? does this sound like a plan to you? BTW i broke the tan wire connection (near the tank, it was already spliced) and that did not change the position at below empty. i imagine that the loss of ground is the overriding element at this point. i suppose i will find out when i jump the connection.
 

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Yeah, something's going on around the gage or the gage itself. The broken tan lead should have sent the gage to full.
Off the back of the gage you should be able to control the tan terminal. If the sender gage terminal (where tan connects) is open, the gage should go super full. If you short it to ground, it should go empty. Hanging a 45 ohm, 5 watt resistor between the terminal and ground should give you 1/2 full.
 

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Discussion Starter · #12 ·
loosened more dash bolts and pivoted the dash forward just a tad more. put the connector on and was reasonably sure it was seated okay but got nothing on the gage. unplugged it, put jumper wires pink, black and tan from plug to gage where i was certain i had good contact. gage moved up to probably where it should be, disconnected the tan and it spiked. rehooked it and it stays spiked, disonnected ground it still stays spiked. it seems like it should have gone back to a normal reading when i reconnected everything, i'm getting baffled by this one. should i remove the gage, get it up where i can see everything and go from there? i will wait for you thoughts.
 

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Hook up pink to the gage with your jumper. Hook the gage ground terminal to a good frame ground with a jumper. Leave tan disconnected. Turn key on. Does the gage go to full? What does it read? Sorry I don't understand "spiked".
 

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Discussion Starter · #14 ·
sorry, a "spiked" gage is one pegged all the way up, in this case above full. so as soon as i dropped the tan connection it went above full but now it wont come back down even when connected correctly (using the jumpers). should it have gone back to normal reading when i reconnected the tan? or does it have to be reset somehow?
 

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Discussion Starter · #16 ·
yes it did. i grounded tan and it dropped back down. after walking past a spare fuel gage still laying on workbence all week i finally noticed it (DOHH) and tried it out. at first it didnt work either, it jumped to above full as soon as i hooked it up. which now made me question the continuity on the tan wire from the sending unit to the gage. i made a long jump wire and ran it from the gage back to near the splice and tested it to make sure tan wasnt broken. it checked okay. i retested the spare gage and this time it worked. was going to change it out with the one in the dash but tried one more time to fit the connector on it. bingo this time it worked too. the only thing i can figure out is that due to the inability to see the connections i must not have been fitting that connector on the gage right. anyhow if it is still working okay in the morning i'm going to button it up and keep my fingers crossed. in any event i learned a lot about how that gage works such as loss of ground = blow empty and loss of signal = above full. thanks a ton for helping to walk me through this. by your posts i assume this is not a hobby for you but you are a professionial electrician? do you only work with vehicles or do you do general electrician work?
 

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Originally posted by 79943:
in any event i learned a lot about how that gage works such as loss of ground = blow empty and loss of signal = above full. thanks a ton for helping to walk me through this. by your posts i assume this is not a hobby for you but you are a professionial electrician? do you only work with vehicles or do you do general electrician work?
Actually the sender unit in the tank is a rheostat. When the tank is full the float moves up to 90 ohms. When the tank is empty it moves to ground (0 ohms). There's no signal. Just an "open" or shorted tan wire.
Guess I've done a little of both of those over the years.
 

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Discussion Starter · #18 ·
so if you wanted to test this would you put your meter on resistance, touch pink and tan and read the resistance between them? the closer to full the higher resistance you should read?
 

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Not quite.
Tie 12 volts to the "pink" terminal.
Tie ground to the "ground" terminal.
Tie the "tan" terminal to ground. Gage reads empty.
Tie a 45 ohm resistor from the "tan" terminal to ground. Gage reads 1/2 full.
Tie a 90 ohm resistor from the "tan" terminal to ground. Gage reads full.
Open the "tan" terminal. Gage reads super full.
 
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