flathead ford temp sender question.

Well, I have just purchased new temperature sensors, and alas they still aren't working. The guage rests at hot and goes all of the way to cold when the lead is grounded, so I am pretty sure it works.

right now, i have the wire from the sender going to the tall pole on the drivers side sender, then a jumper from the DS short pole to the single pole sender on the other side. I have tried reversing them but to no avail. should either of these senders be grounded on the firewall? (dumb question, but is was when i got the car)


diaghram;
^ tall pole on DS sender
* short pole


--to gauge--- ^ *---to pass. side sender ----*--??---ground----???

 

nobody?

 

The senders shouldn't be wired to anything except the gauge. They ground to the block where they thread in.

 

You might find something here.

http://www.vanpeltsales.com/FH_web/flathead_drawings_electrical.htm

 

Did you use teflon tape when you put them in the heads? Could be bad ground...the two prong one is just a thermal switch, the single prong one is the actual sender...

 

Is the car a 6 volt,positive ground,reversed polarity?Some guages will not work properly when changed to neg. ground,Had to change an old 40`s army power wagon back to pos ground so the gas guage would work.I have check out procedures if you need them...............If I can find them

 

I have prints and troubleshooting guide if you need them. PM me your e-mail addy and I'll e-mail them to you....about 5-6 pages.

 

The Ford guages, apart from the ammeter, don't care about polarity. It's current through a bi-metallic strip that heats & bends an arm which moves the needle - the bi-metallic strip doesn't care which way the current flows through it - it gets hot regardless.

 

Here's a good schematic

 

After seeing a couple of half cooked flatheads as a result of the temp guage "averaging" the readings from the two senders, I put in a second guage. Now I read each bank individually so I know if I have a problem

 

Putting in a second gauge is fine - I did it in my 34. One side will normally always be slightly hotter than the other in a flatty - usually the driver's side.

But your assertion that the two senders "average" the reading is inaccurate. The two-prong "sender" isn't a sender at all, it's a switch. It is a normally closed, temperature-sensing switch - when the engine overheats (I forget the actual setting of the switch, but want to say 210* or 205*??), it opens & sends the gauge to full hot (like it is when the key is off) because there is no current through the real sender on the other side to comlete the circuit to ground.