I have a 1956 F100 with a 1957 312 engine. All of the gauges work except the engine temp. I put a new temp sensor in for a 1957 engine (12v) which is much smaller than the 1956 sensor which won't fit in the hole. I think the gauge is ok since when the engine is off the needle goes to hot and when it starts it moves to cold but it stays there even if the engine is run for awhile. Is the 1957 sensor not compatable with my 1956 gauge and if not do you have any suggestions how I can rig a system to make this work with the stock gauges. I have seen an "adaptor" listed for sale but I don't know how that would work for my situation since the '56 sensor is too wide for the hole it's supposed to fit into. As always thanks in advance.
Chris

 

Many malfunctioning sensors/gauges can be traced back to people using teflon sealing tape on the threads when installing the sensor. This quite effectively insulates the sensor from the ground path it needs to work. The sensors have a pipe thread on them that is self sealing requiring no sealant. If you have used a thread sealant, try removing the sealant and using a wire brush designed for cleaning battery terminals (use a separate one that hasn't been used on a battery) or the insides of copper pipes before soldering to clean the threads in the engine nice and clean and bright before reinstalling dry.

 

I was thinking of adding an addendum to my post because I indeed do have teflon tape on the threads. Is that enough to insulate the sensor so that it won't ground appropriately?

 

Yes, definitely! No sealant is required just snug it down tight.

 

Thanks I will take it off tonight when I get home from work. Now I will have even a harder time concentrating at work than usual because I want to hurry up and get done so I can get back the the real work-my truck!

 

No, work is something you do when you'd rather be doing something else.

 

Really!

I mean, if it was something you really WANTED to do; they probably wouldn't pay you, you'd likely have to pay for admission.

 

Amen. It's a good thing that people can't read minds or I'd probably get fired for goofing off.

 

Ax, Since you mentioned the issue about teflon tape I was thinking about the oil pressure sendor. I think that I put tape on that as well, will that screw up it's function or is it ok to leave it the way it is? The light comes on when you are cranking the engine but goes out when it is running. Also is there a way to tell if my battery is draining when the truck is off-without letting it go dead-most of the time I wind up disconnecting the positive cable if it is going to sit between drives for several hours just in case.

Chris

 

Yes, it will mess up the OP sender as well. Guess how I found that out...
The easiest way I know to check for drain is with a VOM. Turn everything off (some items that are forgotten: clock, newer stereo with electronic tuners and station settings, alarm systems, remote keyless entry) Disconnect + battery cable and put VOM in series on amps setting. If the meter reads a current flow, start pulling and replacing fuses one at a time until you get no current indicated (<1 amp current flow can drain a battery in a few days). Whatever the fuse you pulled that shut off the current flow is the culprit circuit. look for chaffed wires, stray wire strand at connection. If you don't see anything, replace fuse and start disconnecting connections at devices. replace any device that is shorting out. Sometimes you can get a feedback through the alternator circuit. With engine off, disconnect the wire from the power feed stud on the alternator and see if current stops flowing.
A heavy draw starter with low amp charging circuit and short running time or mostly idling between starts can pull down a battery as well.

 

Thanks for the tips. Now my weekend plans are looking full!

 

If you don't have acces to a VOM. You can do a down and dirty with a test light (if you dont have one of those...build one out of a spare tail light bulb and some wire)

Hook it up the same as AX described. Luckily, on our trucks there's not too much that can drain the batteries.

Let us know what you find
Bobby

 

A low trickle leak to ground may not be high enough to light a light bulb, but could still drain the battery. I use the A scale first, then if there is any needle movement check it with the mA scale setting. A decent serviceable VOM can be purchased for 10-20.00 at your local Lowes or HD. Check in the low voltage electrical dept. Once you own one you'll wonder how you did without it. I have 3, one at work, one in the house and one in the garage and use them regularly.

 

Good point AX. I have several VOM's also, 1 digital, and 2 analog. I also have several test lights, one of which is super sensitive. It is an older Snap-on with a funky bulb. It is so sensitive that it will light up on what the factories (GM)call normal drain (50 milliamps and less) The bulb resembles a glass tube fuse.

I got to where I would use a test lamp with a regular bulb (the long skinny dome lamp bulbs) to test for draws. If the bulb lit up bright, you could bet the draw would be a light on somewhere, trunk, glove box, etc. If the light was on dim, then I could usually trace it to a component.

I agree though, the best way is to use a meter.
Bobby

 

I am wrapping up the final touches on a complete rewire of my 55 installing an EZ21 kit. Could not get my temp gauge to register and luckily came across this thread. Yes I added teflon tape and the gauge did not work. Removed the tape and reinstalled the temp sender and working like a charm. Ax gets the nod of the day. Once again FTE helps out on my project. Thanks, Joe