I have a 76 f100 with a 351 c 4v from a 71 mustang. I put in a new temp sending unit for a gauge. now it just reads hot. I tried another gauge cluster same thing . I better give ya some info, I am running a wire from sending unit to the red / white wire in connecter coming from the wires running to fire wall which should be the correct wire.

What is wrong?

 

Is the sending unit you installed for a 76 F100 (whatever engine was original) or for whatever the 351C came out of. Sending unit needs to match the gauge.

 

Doesn't make any difference because the same temp sending unit was used for all...with a temp gauge.

F1SZ-10884-A (replaced DOWY-10884-A & DOZZ-10884-A) .. Temperature Sending Unit-Use with Temp Gauge (Motorcraft SW-2328).

Applications: 1970/96 F100/350, Bronco & Econoline / 1997 F250/350 / Myriad 1970/90's FoMoCo Passenger Cars.

 

Either your sending unit is for a light and not a gauge, or the engine is actually running hot.

 

It is suppose be one for a gauge not an idiot light

 

It's supposed to be...but is it? Auto parts store parts cluck coulda sold you the wrong sender. See post 3 for the correct sending unit/applications.

 

Checking to see which one was sold to me.

 

Is it just it just the way i am tapping into the wire? I am taking a wire from the sending unit to the plug from the firewall. It is a 3 prong plug. I am just sticking the wire into the red/white one which should be the correct one.Should I be doing something else also? What are the other wires for in the connecter?

 

The bottom of the temperature gauge runs out to the block through a RED with WHITE stripe wire. You control the needle swing by varying the resistance to ground. How do you know you have the correct sending unit? How do you know the engine isn't actually running hot? Seems like we're not any farther along than when we started.

If you disconnect the sending unit and turn the key on, does the gauge fall back to the left? If so, there's nothing wrong with the wiring. It's all in the sending unit. I don't know what connector you're talking about.

 

Yes it swings back to left. I looked up the schematic in Chiltons.

 

Okay, then my original statements still hold true. Wrong sending unit, or engine is really at that temperature. If there were a short in the wiring, the gauge would peg toward H regardless of the sending unit downstream being connected or not. You've proven that not to be the case.

 

I know this is old, but how can you vary the resistance to ground? Are you just coiling up some thinner gauge wire and adjust the length till it's where you need it? Thank you!

 

In the sender there could be a variable resistor (like a fuel gauge) the changes resistance by expansion/ contraction with heat.

 

By installing a fixed value resistor in series. This might work if the gauge is reading inaccurately on the high side. Many of the older Ford gauges are a little less than accurate by now. I believe there is some adjustment that can be made to the gauge indication itself too, but you better have a steady hand and avoid coffee that day.

 

Thanks for the replies! I understand the fixed resistor. How do you adjust the indicator itself or the variable resistor if it has one? Thanks again for the help Guys!