What am I doing wrong? (Wiring)
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Laughing Gas
Joined: Feb 2004
Posts: 1,080
Likes: 1
From: Elsinboro, NJ
What am I doing wrong? (Wiring)
I wired up a relay to that should in theory give me reading from both fuel tanks. Diesel when diesel pump is on Vegi when Vegi pump is on. Here is how I wired it.
When I tested it with the enginge off it worked, now after I have soldered everything in place it just reads full all the time. Now the Vegi tank is full so I thought the relay was sticking so I put in a different one and and still reads full all the time.
Any suggestions?
Mike
When I tested it with the enginge off it worked, now after I have soldered everything in place it just reads full all the time. Now the Vegi tank is full so I thought the relay was sticking so I put in a different one and and still reads full all the time.
Any suggestions?
Mike
Senior User
Joined: Aug 2011
Posts: 301
Likes: 1
I wired up a relay to that should in theory give me reading from both fuel tanks. Diesel when diesel pump is on Vegi when Vegi pump is on. Here is how I wired it.
When I tested it with the enginge off it worked, now after I have soldered everything in place it just reads full all the time. Now the Vegi tank is full so I thought the relay was sticking so I put in a different one and and still reads full all the time.
Any suggestions?
Mike
When I tested it with the enginge off it worked, now after I have soldered everything in place it just reads full all the time. Now the Vegi tank is full so I thought the relay was sticking so I put in a different one and and still reads full all the time.
Any suggestions?
Mike
You see with that type of relay you should never have to fill your tanks again it saves you so much fuel! lol
Senior User
Joined: Jul 2006
Posts: 395
Likes: 0
From: New Hampton, IA
That diagram is correct. When you turn the veg pump on do you feel the relay click? I would test the resistance across the relay (between 87a and 30 then 87 and 30 when on) to make sure the relay is not introducing resistance into the circuit.
Senior User
Joined: Mar 2012
Posts: 492
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From: Jenkintown, PA
Not sure where the problem is, but your wiring diagram is correct.
I would start by double and triple checking all of the connections. If everything looks good, use an ohmmeter to read the resistance of the individual sending units (relative to ground) at the relay. Then move your meter to the IP and make sure you are seeing the same resistance values at the factory fuel gauge as the relay is toggled on and off.
I'm not 100% sure, but I think that a high resistance translates into a full tank and a low resistance is empty. If this is correct, then your false full reading would indicate an open circuit somewhere.
Chris
I would start by double and triple checking all of the connections. If everything looks good, use an ohmmeter to read the resistance of the individual sending units (relative to ground) at the relay. Then move your meter to the IP and make sure you are seeing the same resistance values at the factory fuel gauge as the relay is toggled on and off.
I'm not 100% sure, but I think that a high resistance translates into a full tank and a low resistance is empty. If this is correct, then your false full reading would indicate an open circuit somewhere.
Chris
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Laughing Gas
Joined: Feb 2004
Posts: 1,080
Likes: 1
From: Elsinboro, NJ
I felt like Clark Griswald, I checked, rechecked and even had Russ check.
Now I went out unplugged the relay and turn the truck on. It still read full with no signal going to the gauge at all. After about a 30 seconds I heard the low fuel light and chime go off. I turned off the truck and plugged the relay back in. Turned on truck with diesel tank selected and it read 1/4 tank. Switched to Vegi tank and it read full, back to diesel 1/4 tank. Rinse and repeated about 10 times and it all worked.
Who the heck knows, but I knew my solder connections and wiring was right......
Now I went out unplugged the relay and turn the truck on. It still read full with no signal going to the gauge at all. After about a 30 seconds I heard the low fuel light and chime go off. I turned off the truck and plugged the relay back in. Turned on truck with diesel tank selected and it read 1/4 tank. Switched to Vegi tank and it read full, back to diesel 1/4 tank. Rinse and repeated about 10 times and it all worked.
Who the heck knows, but I knew my solder connections and wiring was right......
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Senior User
Joined: Mar 2012
Posts: 492
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From: Jenkintown, PA
The open circuit seen by the fuel gauge while you were wrapping up your work would have made it read full if the ignition was left on. When the relay was put back in it might have taken a while for the resistance value to register due to the delay built into the gauge. My 97 E350 takes a long time to display a change in fuel level, especially if the ignition is in the run position.
Chris
Chris
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Laughing Gas
Joined: Feb 2004
Posts: 1,080
Likes: 1
From: Elsinboro, NJ
Well I drove to work this morning. Started off on diesel it was reading correctly at 1/4 tank. Switch to vegi after the first two miles and the went to full. Stopped at Wawa for coffee turn truck off got back it started up read full. Got a mile from work switched back to diesel, the gauge never moved off of full. Got in the truck a few hurs later drove on diesel and it still read full.
So I guess I still have the same problem.
The ground for the relay and the vegi sender is on a screw in the frame. Any thoughts of soldering the ground wire for the vegi sender to the logic ground wire of the diesel sender? Or do you thing having the two ground on the same would cause problems? I know it sounds stupid but I'm usually electrically inclined, and this is bothering the crap out of me.
So I guess I still have the same problem.
The ground for the relay and the vegi sender is on a screw in the frame. Any thoughts of soldering the ground wire for the vegi sender to the logic ground wire of the diesel sender? Or do you thing having the two ground on the same would cause problems? I know it sounds stupid but I'm usually electrically inclined, and this is bothering the crap out of me.
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