gauges go to max when key on

dwebster8783 · Post by **dwebster8783** » Wed Dec 19, 2007 10:03 pm

I have a 70 ford f100 ranger. I just installed a new sending unit in hopes that would get me fuel gauge to read right but now my temp and oil gauges go to max when the key is on. I put the old sender back in and still the same. anybody have this happen before?

Post by **FORDification** » Wed Dec 19, 2007 11:15 pm

Sounds like the IPVR (instrument panel voltage regulator) has gone south. This is mounted to the back of the instrument panel, and converts 12V power to a 5V pulse to power the gauges. However, simply changing a sending unit wouldn't affect the IPVR. Did you do any messing around with the wiring?

fordman · Post by **fordman** » Wed Dec 19, 2007 11:16 pm

well usually when you have fuel guage problems you can adjust the ipvr. on the back of the guages and it will sometimes fix the sending units reading problems. it sounds like you could have messed up the ground for the system. since it was working better before you messed with it. i would try to wiggle the ground wire on the sending unit to see if it comes back to normal. and then go to this page and restart your diagnosis. http://www.fordification.com/fuel-sending-units.htm

heep70 · Post by **heep70** » Thu Dec 20, 2007 6:29 am

Would the IPVR make the needles wiggle? Mine sometimes start wiggling not from one side of the gauge to the other. Just in the same general area. They will wiggle really fast.

rjewkes · Post by **rjewkes** » Thu Dec 20, 2007 1:06 pm

i'm wondering what would make just the oil sending unit/guage peg out? it grouds out right when you pull the wire and ground it the needle goes to High.

but if plugged into the sending unit sometimes it reads right sometimes it only goes to high when you are down 2 quarts.

i know i have the sending unit for full instrument. is the replacements set up for the opposite of the original?

cause it pegs with just the key on and is the only instrument doing this.

fordman · Post by **fordman** » Thu Dec 20, 2007 7:38 pm

greg i would guess at voltage spikes making the wiggling. robert mayeb the sender or the guage by itself is going bad.

dwebster8783 · Post by **dwebster8783** » Thu Dec 20, 2007 7:55 pm

ok so since I had no work today I pulled the truck into the shop and spent all day working on this and got no were. what I have found out sofar and what I have done:
I installed a new
ground wire at the fuel sender
engine to frame
engine to body
engine to battery
new pos batery cables
traced wires from oil and temp senders to instruments checking for broken wires and found no problems
changed the ipvr 5 times with others that I know worked just fine
checked voltage at the back of the gauges when key on which is pulsing 4.87 volts
checked continuity accross circuit board to each gauge from ipvr which tested good.

one question I have is the purple wire on the instrument connecter. is this supposed to be a full 12 volts or lower. Mine measures 8.46 volts. and where does this wire go to from the intrument plug. I traced it back as far as behind the radio and i lookslike it keeps going towards the heater. it does not look like a regular wire either. I believe its a fusable link.

thanks any help would be great!

Dan

dwebster8783 · Post by **dwebster8783** » Fri Dec 21, 2007 11:38 am

Fordman
I went to the fueltank sender page you posted. My fuel gauge works for the most part so that wont really do me much good. I am having the most problems with my oil and temp gauges right now.

dwebster8783 · Post by **dwebster8783** » Fri Dec 21, 2007 11:46 am

I installed another oil gauge and temp gauge this morning. I was feeling good about the problem. turned key on and they pegged right away. so once I get beck form the doc appointment this morning I will be back at it.

does anybody else have spme ideas. I would hate to go out and buy new senders because I know they are good. already put my meter on and checked them.

Thunderfoot · Post by **Thunderfoot** » Fri Dec 21, 2007 1:58 pm

one question I have is the purple wire on the instrument connecter. is this supposed to be a full 12 volts or lower. Mine measures 8.46 volts. and where does this wire go to from the intrument plug. I traced it back as far as behind the radio and i lookslike it keeps going towards the heater. it does not look like a regular wire either. I believe its a fusable link.

That would be the Exciter wire for the alternator it should be also connected to the Amp Gauge... it's a risistive wire for trucks with gauges... so ok there...

When I get home tonight I'll look over your information more and see if I can figure anything out that might help... if you don't get it fixed by then...

dwebster8783 · Post by **dwebster8783** » Fri Dec 21, 2007 4:00 pm

I know the purple wire goes to the ipvr on my instrument cluster. I will have to see if it goes to the alt. I was just looking at those wires and dont recall seeing a purple wire.

I just checked a few more things. should I have continuity between the gauge terminals and the metal case that the gauges and circuit board mount to? my amp gauge has red plastic spacers but all the other gauges have a thin piece of paper product. is this normal?

fordman · Post by **fordman** » Fri Dec 21, 2007 6:53 pm

have you tried to turn the screw in the back of the ipvr?

dwebster8783 · Post by **dwebster8783** » Fri Dec 21, 2007 10:37 pm

yes that was one of the first things I tried. it would effect the fuel gauge but not the oil or temp.

fordman · Post by **fordman** » Fri Dec 21, 2007 10:53 pm

i am sorry . everytime i get on here the past few days some idiot comes in the room adn wont shut the f up. i will keep trying to help but i cant until she shuts up.

Thunderfoot · Post by **Thunderfoot** » Fri Dec 21, 2007 10:57 pm

dwebster8783 wrote: I just checked a few more things. should I have continuity between the gauge terminals and the metal case that the gauges and circuit board mount to? my amp gauge has red plastic spacers but all the other gauges have a thin piece of paper product. is this normal?

No, there should be no continuity there. That will ground them which is how the Temp and Oil Pressure sending units work. They act like a variable resistor to ground, the closer to a short to ground the higher the gauge reading so if it is grounding right at the gauge then it will peg out like you are seeing...
Do you get this with the wires still attached to the truck or just with the instruments cluster out of the truck, no connection to the truck wiring?

If you still have the truck wiring hooked up try unhooking them and see if you get the same reading. Also, you can check the wires to the engine to see if they are shorted to ground and if they are unhook the wires at the sending units and recheck. If they are still grounded then you have a short somewhere in them to ground...

Hope this is not confusing

If you have any questions on this let me know.

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