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Glover
Samba Member
Joined: April 25, 2018
Posts: 5
Location: Maple Ridge BC
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 Posted: Fri Sep 21, 2018 6:46 pm Post subject: 1971 gas gage shows full |
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| My gage goes straight to full all the time, I was told that there may be a grounding issue. Has anyone had this issue and do I need to remove the tank to resolve the issue? |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51150
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Fri Sep 21, 2018 6:51 pm Post subject: Re: 1971 gas gage shows full |
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Start by confirming the brown wire isn't pinched where it emerges from the tank cover panel near the voltage regulator (lower RH corner).
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aeromech
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Joined: January 24, 2006
Posts: 16971
Location: San Diego, California
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| Posted: Sat Sep 22, 2018 7:57 pm Post subject: Re: 1971 gas gage shows full |
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If I remember right, the sender adds resistance which actually makes your gauge read lower. So when the sender is disconnected, the gauge reads full deflection. So check to make sure the wire between your sender and gauge are connected
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Glover
Samba Member
Joined: April 25, 2018
Posts: 5
Location: Maple Ridge BC
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| Posted: Sun Sep 23, 2018 8:30 am Post subject: Re: 1971 gas gage shows full |
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| Thanks for the information, really want the gage to be working before we take our trip south to California! |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51150
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sun Sep 23, 2018 9:12 am Post subject: Re: 1971 gas gage shows full |
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| aeromech wrote: |
| If I remember right, the sender adds resistance which actually makes your gauge read lower. So when the sender is disconnected, the gauge reads full deflection. So check to make sure the wire between your sender and gauge are connected |
That's on GM products, the VW shows fuller as resistance increases. Disconnected = empty, grounded = full.
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SGKent 
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Sun Sep 23, 2018 2:13 pm Post subject: Re: 1971 gas gage shows full |
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the float falls as the tank level goes lower. The float has arms on a 1971 that short across the resistance wires. The lower the float it the longer the wire hence more resistance. This confirms BusDaddy's full = less resistance.
On splits at leas the floats used to stick on the wires and then you'd hit a pothole and the tank would go from 1/2 full to 1/8th full etc.. As I recall on my 1971 the gauge would read empty when it got a bad connection. I would think reading full all the time would be a pinched sender wire but I guess a float could stick in the up position.
Tell me (for anyone), if the sender and sender ground wires are reversed and someone reverses the two wires when hooking it up wouldn't that cause it to read full also? Essentially the sender wire would be connected to the sender ground.
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51150
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sun Sep 23, 2018 3:02 pm Post subject: Re: 1971 gas gage shows full |
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| SGKent wrote: |
| Tell me (for anyone), if the sender and sender ground wires are reversed and someone reverses the two wires when hooking it up wouldn't that cause it to read full also? Essentially the sender wire would be connected to the sender ground. |
Yes it would, although the ground wire on the tube sender tanks has a ring terminal so it's impossible to mix up (unlike the later ones).
You are right, I should have said "resistance increases as the level drops", or "continuity decreases", whatever, less ground near empty, completely grounded at full.
If you don't look carefully for the striped brown wire and connect any old plain brown wire to the G terminal it'll read full all the time. The wire from the sender doesn't pass through a grommet where it leaves the tank compartment, it's got double thick insulation and there's a flattened area on the panel to let it pass through, but if someone got it in wrong and pinched it you'll get a perpetually full tank. There's a connection near the voltage regulator you could unplug to confirm, if the gauge drops the issue is in that wire or in the tank. If none of that works it's time to move up front under the dash, plenty of places to get in trouble there.
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Glover
Samba Member
Joined: April 25, 2018
Posts: 5
Location: Maple Ridge BC
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| Posted: Mon Sep 24, 2018 3:56 pm Post subject: Re: 1971 gas gage shows full |
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it has been repaired! It was grounding in the dash. insulated the connector and now she seems to be working.
Thank you for the information.... couldn't have don it without u guys |
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TomWesty
Samba Member
Joined: November 23, 2007
Posts: 3482
Location: Wyoming,USA
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| Posted: Mon Sep 24, 2018 9:11 pm Post subject: Re: 1971 gas gage shows full |
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| Glover wrote: |
it has been repaired! It was grounding in the dash. insulated the connector and now she seems to be working.
Thank you for the information.... couldn't have don it without u guys |
My bus runs so much better because of these guys.
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