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aftermarket gauge question

bcrump5252

Full Member
Joined
Nov 26, 2005
Messages
261
Loc.
high point
got a newb question? I got aftermarket gauges for my B-day yesterday and the guy at the auto parts store told me I needed " diodes" in my ground wires so I didnt get any bleed over, and I would also need two resister's for my duel fuel gauges? Im running 2 fuel gauges so I dont need the electric switch. does anyone have any feedback as to if this is right or not, and how I might go abotu hooking these duel fuel gauges up?

any help would be greatly appreciated bro's

P.S. if I could post pics of my truck on here I would sorry.
 

surfer-b

Contributor
Bronco Guru
Joined
Sep 7, 2006
Messages
2,972
bcrump5252 are the gages elctronic if so yes diodes will be needed which are used in almost all electronic equiment. Diodes are to in most cases to allow current to pass only in one direction, except for zener diodes, they will be hooked up on the power input side of the gage to protect from in case the wires of the batt are hooked up in reverse. i have seen a Electrical ENG. post on here from time to time maybe he can help out here in more detail i am giving you the knowledge i remeber from my ENGR circuits class on diodes which is not much. maybe find a good car audio installation center and talk to them. Sorry for the long parag.
 

bronko69er

EB Addict
Joined
Oct 16, 2006
Messages
4,599
Loc.
Renton, WA
I assume the fuel gauges are designe for a ford?
Did they come with a manual saying what tyle of input they require to read full/empty?
I believe the bronco sending units read 10 ohms full and 70 ohms empty. (somone will correct me if I'm wrong.)
If your gauges require higher resistance reading you would have to add resistors.
Which gauges did the guy tell you to install diodes with?
I wouldnt think the tripple gauge set needs any additional compontens
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,834
Your parts guy is full of it. No diodes are needed unless you are doing something real funny. I once had a cooling fan that would coast down and cause strange problems, but it wasn't wired right to begin with.

Resitors, only if he sold you the wrong gauges. Aftermarket gauges need switched power, ground, power for the light if you want to see them at night, and the wire to the sensor. They don't even use the stock insterment voltage regulator.
 
OP
OP
B

bcrump5252

Full Member
Joined
Nov 26, 2005
Messages
261
Loc.
high point
the only gauge I can think of is the fuel gauge, becase i ground it then hook the sender wire to it and then hook a 12v source to it, so wouldnt that be to much voltage for the sending units?
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,834
bcrump5252 said:
the only gauge I can think of is the fuel gauge, becase i ground it then hook the sender wire to it and then hook a 12v source to it, so wouldnt that be to much voltage for the sending units?

You better not be putting a 12V feed to the sender, you will fry it. The gauge should have a wire on it for the sender. It will have some voltage coming out of it. Don't know how much, I didn't design the thing. The sending unit is a varible load on that sender wire. There is a pull up resistor inside the gauge (not that you need to worry about). Depending on the resistance of the pull up resistor, and the resistance of the sending unit there is a direct corolation to the voltage in between the two. That voltage is what the gauge reads and is calibrated in E to F.

Take an ohm meter and measure the resistance of the sender wire to ground. it should be between 10 and 70 ohm (not k-ohm or m-ohm). If you get that your sender should be good.

Next take the gauge. Hook up power and ground. Take the sender wire and touch it to ground. when you touch it toground the gauge should peg at full. If you happen to have a few spare resitors in the 10 to 70 ohm range laying around, try grounding the gauge sender wire through the resistor. Get different gas gauge readings. Now hook the gauge to the sender and you will have a working gas gauge.

Note that all grounds must be common. testing the gauge with a battery on the ground won't do anything with the sending unit in the truck unless that test battery and the truck have the same ground.
 
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