Multimeter Idiot
Fleet Mechanic
Joined: Aug 2010
Posts: 1,994
Likes: 3
From: Morgan Hill, CA
I think I see what's going on...
On the aftermarket gauges, 12v power goes in to the gauge. The gauge itself is a load, so there will be a 12v drop through the gauge. The path to ground determines what the gauge will read. What that all means is that it might appear to have zero volts at the wire going from the gauge to the sending unit. That wire is really just a ground path for the gauge. The sending unit is a variable resistor that is in that ground path. You need it to be that 33/240 ohm sender.
You could do a test by buying some resistors at Radio shack...you can string them together (in series) to add up to 33 ohms. If you attach the resistors to the sending unit wire and touch it to a ground, the gauge should read empty.
Are there any adaptors that will allow you to use the hole that is already in the mustang tank??
Dan
On the aftermarket gauges, 12v power goes in to the gauge. The gauge itself is a load, so there will be a 12v drop through the gauge. The path to ground determines what the gauge will read. What that all means is that it might appear to have zero volts at the wire going from the gauge to the sending unit. That wire is really just a ground path for the gauge. The sending unit is a variable resistor that is in that ground path. You need it to be that 33/240 ohm sender.
You could do a test by buying some resistors at Radio shack...you can string them together (in series) to add up to 33 ohms. If you attach the resistors to the sending unit wire and touch it to a ground, the gauge should read empty.
Are there any adaptors that will allow you to use the hole that is already in the mustang tank??
Dan
Tuned
Joined: Feb 2012
Posts: 462
Likes: 5
From: Kalamazoo, MI
Thanks HKYswim - That gives me a place to start. It's always challenging to solve the mystery of why someone else wired it a certain way. I know it doesn't work so now dig until we get it working..
This is a picture of the deal we used to splice the third brake light wire
back together - Is this the way you guys would do a splice? Or would you do the screw cap thing or solder it?
Ben in Austin
(I'm not typically this dense - I've done mechanical things just not electrical - thought I'd take the opportunity for some on the job training).
This is a picture of the deal we used to splice the third brake light wire
back together - Is this the way you guys would do a splice? Or would you do the screw cap thing or solder it?
Ben in Austin
(I'm not typically this dense - I've done mechanical things just not electrical - thought I'd take the opportunity for some on the job training).
Do not use this style of connector, it cuts the wire creating a weak/breaking point. I solder and heatshrink all my connections, (but that my Robotics background). you can use Butt or Barrel Crimp style.
Tuned
Joined: Feb 2012
Posts: 462
Likes: 5
From: Kalamazoo, MI
Thread Starter
|
Logistics Pro
Joined: May 2010
Posts: 3,793
Likes: 19
From: Austin
Hey Wavetrain,
Thanks - Our current after market fuel guage mismatched to the 1970 sender unit - shows a range from buried Full down to about 3/4's full for empty. I haven't tried to change the resistance in the line as I know what the real solution is - It's bothering me that it doesn't work right.
I have to get it right - it's a personal problem - plus I have "cheap" 20 year old son labor. I just need to make sure he doesn't blow up doing it.
So..... What's the safest way to cut a sender hole in the top of a gas tank that recently held fuel & has active fumes?
Ben in Austin
1950 F1
(P.S. - I'll try your radio shack ohm resistor just to see what it does to the reported gauge range - I'm curious).
Thanks - Our current after market fuel guage mismatched to the 1970 sender unit - shows a range from buried Full down to about 3/4's full for empty. I haven't tried to change the resistance in the line as I know what the real solution is - It's bothering me that it doesn't work right.
I have to get it right - it's a personal problem - plus I have "cheap" 20 year old son labor. I just need to make sure he doesn't blow up doing it.
So..... What's the safest way to cut a sender hole in the top of a gas tank that recently held fuel & has active fumes?
Ben in Austin
1950 F1
(P.S. - I'll try your radio shack ohm resistor just to see what it does to the reported gauge range - I'm curious).
Posting Guru
Joined: Jul 2012
Posts: 2,203
Likes: 4
From: Southern SC.
The safest way - have some one you don't like do it 
Wash the tank 2 or 3 times then fill it with water and let it stand over night totally filled to the point of spilling. Then still say a prayer. Dave S
Wash the tank 2 or 3 times then fill it with water and let it stand over night totally filled to the point of spilling. Then still say a prayer. Dave S
Logistics Pro
Joined: Apr 2010
Posts: 3,577
Likes: 29
From: Pekin, IL
I had to fix alot of trailer wiring....most of the problems I encountered were these connectors. 3M calls them "ScotchLoks" most of the issues were corrosion problems, some were wires that were cut by the little blade piece, over time, the movement\bounce of the trailer would break the already "damaged" wire.
I wish I had a dollar for everyone of those I repaired.
Fleet Mechanic
Joined: Aug 2010
Posts: 1,994
Likes: 3
From: Morgan Hill, CA
I know this has been mentioned several times, but I want to add to the "agreement" about these connectors. I was a Mobile Repair Mechanic for U-Haul
I had to fix alot of trailer wiring....most of the problems I encountered were these connectors. 3M calls them "ScotchLoks" most of the issues were corrosion problems, some were wires that were cut by the little blade piece, over time, the movement\bounce of the trailer would break the already "damaged" wire.
I wish I had a dollar for everyone of those I repaired.
I had to fix alot of trailer wiring....most of the problems I encountered were these connectors. 3M calls them "ScotchLoks" most of the issues were corrosion problems, some were wires that were cut by the little blade piece, over time, the movement\bounce of the trailer would break the already "damaged" wire.
I wish I had a dollar for everyone of those I repaired.
Elder User
Joined: Jun 2012
Posts: 661
Likes: 0
Hello Ben, were you ever able to find a chart ( a factory chart ) of the resistance values of Ford sending units? I would like to verify that Ford 81-86 would have been the same.
I just called the local Ford dealer and sure enough the gauges carry the same part # from 1980 -1986 on all lines of trucks from F-150 - the 350 series, if that is the case than I guess it would be safe to assume that since the gauge and the sending unit has to be paired that no matter the drivetrain wether it be 6 cyl or 8 the gauges and sending units would all carry the same values. What do you think ?
Clearly the sending units are not identical, I have pulled enough of them now to see there appearances vary but that would be on account of fuel tank changes such as size, pick-up location whatever.
I just called the local Ford dealer and sure enough the gauges carry the same part # from 1980 -1986 on all lines of trucks from F-150 - the 350 series, if that is the case than I guess it would be safe to assume that since the gauge and the sending unit has to be paired that no matter the drivetrain wether it be 6 cyl or 8 the gauges and sending units would all carry the same values. What do you think ?
Clearly the sending units are not identical, I have pulled enough of them now to see there appearances vary but that would be on account of fuel tank changes such as size, pick-up location whatever.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Elder User
Joined: Jun 2012
Posts: 661
Likes: 0
Thread Starter
|
Logistics Pro
Joined: May 2010
Posts: 3,793
Likes: 19
From: Austin
Hey 1930,
The peculiarity I ran into for the '70 mustangs is they are
"bi-metallic" & the gauge/sender doesn't function in a linear way.
The gauge shows half 3/4th's of the way across - it's odd. I think you are safe if you stick with senders & gauges from the same era of trucks.
Let me look arond for the write-up on the non-linear bi-metallic senders.
Ben
The peculiarity I ran into for the '70 mustangs is they are
"bi-metallic" & the gauge/sender doesn't function in a linear way.
The gauge shows half 3/4th's of the way across - it's odd. I think you are safe if you stick with senders & gauges from the same era of trucks.
Let me look arond for the write-up on the non-linear bi-metallic senders.
Ben
Thread
Thread Starter
Forum
Replies
Last Post
John & Old Ford
1948 - 1956 F1, F100 & Larger F-Series Trucks
6
Feb 1, 2013 07:36 AM
NormH
1948 - 1956 F1, F100 & Larger F-Series Trucks
3
Jul 24, 2012 03:23 AM