[T3] 73 T-3 SB electrical grounds.

William J catnine09 at dslextreme.com
Thu Nov 9 19:44:32 PST 2017

 I was able to fix most of my FI issues by the 2 case ground trees. 

 Today I decided to fix the horn. It has the plastic pad that snaps down on 4 plastic pegs . The top left I lifed up on a year ago and it would not stay down. I bought new black circle shaped posts years ago to replace the original ones that broke. In the pad each hole has 3 tabs that snap and hold . I found one missing a tab found it and used liquid testors model train cement seems like acetone . I was able to use that and basically it melts this plastic together. I also cleaned the 4 brass tabs and 4 bolt heads now the horn works and the pad stays.

 The odd part is with the engine off and I've tried this several times the horn just makes a slight sound , engine running it works fine which I find odd even with the battery @ 12.72 volts. 

 The next issue is the fuel gauge. since 85 when I bought this car and even when I had the sender out and grounded if I allowed the float to ride on the 2 thin wires the gauge worked perfect . With everything together no matter what the gauge will jump down from 1/2 to 1/4 and from 1/4 to the red area. When this happens I rap the dash on the left side by the gauge and it will respond by moving back where it was or close to it. It's always done this.  

 There are two tree grounds welded to a support left of the column these are the only grounds to the dash and the fuel pump / wipers / T/S / 4 way  light and relay /fresh air fan / clock /. All the grounds end up at these two trees. #10 , # 11 , # 12, & #13. 

 There is this daisy chain that starts at the tree to the Fuel gauge # 12 then to a spade on the speedo then another spade on the speedo to the clock . 

 I added one ground to the Fuel gauge housing on one spring hold down that each gauge has 2 to secure them in the dash. I check with an ohm meter and get .1 to .0 ohm good ground. As a test if I place a jumper wire on the fuel gauge ground 2 brown leads into one female spade and down to the tree under the dash I have 3 to 4 ohm same thing if I place the jumper with the gauge assembly out just the bake light plug I get the same reading yet if I check from the male spade on the back of the black main plug to the female round deal it tests fine. 

 The Bentley shows a brown bar all grounds and shows the 4 numbers I noted in several places . 

 I'm no sure if the 4 way flasher is before the gauges without removing it.

 I have this insane fuel gauge and if I turn on the 4 ways the fuel gauge needle jumps from empty to just past the red mark and continues. I moved the spades and the rear of the bake light with the gauge connected and the one for the tank sender stopped this . Once I tightend it it was right back to fuel gauge jump 4 way on. 

 I even checked the ground to the clock and it also read 4 ohms then placed a jumper on it and it was 0 ohms. 

 Everything works and the wiper draw the most and they work fine and all go to the same ground point . I cannot see a thing wrong with the female spades or their factory  crimps . No tarnish or green brass. nothing. No breaks. 

 I know somewhere is a ground issue and it only seems to affect the fuel gauge . The fuel pump and wipers have their own grounds and they go right to the same 2 ground trees as all the other dash grounds. . Everything else is in this daisy chain. It can't be the spot welded 2 trees the wipers are on one and the fuel pump on the other and they are an inch apart. The Turn signals don't make the fuel gauge jump. I even pulled the flasher one tall black one on the left with 3 spades and one on the far right of the fuse box with 4 or 5 spades . Both plug into the back of the fuse box the key buzzer was in the center and had two terminals and I removed it long ago and the dome light does work. The Buzzer was off fuse #9 16 amp power from the left down switch and ground through the ign key cylinder. 

 I have a extra complete set of gauges and plugged in the one fron the 72 I have and it does the same thing so it's not the fuel gauge. 


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