The Ford Barn

wadsjc · 10-12-2011, 11:55 AM

There are two temp senders on my flathead V8. The one on the driver's side is a single pole and the crossover wire connects it to the 2 pole sender on the passenger side. The second terminal on the passenger side sender connects to the wiring harness. Does it matter which terminal attaches to the harness? One pole is taller than the other. Thanks in advance for your help.

wadsjc · 10-12-2011, 01:53 PM

Some additional information. The temp gage was working OK. I swapped out the starter relay, started the truck and noticed that the temp gage stayed on H - no movement. The coolant is ok and not overheated. The gage just seems to have stopped working. Swapping the two connections to the Dual contact sender doesn't change anything.

gearhead1952 · 10-12-2011, 02:11 PM

There are two type of senders on the truck flathead. The single wire connection is a normal sending unit. The two wire is actually a switch and opens when engine overheats. So if yours is going to hot instantly with the key on then may have a broken wire or maybe a bad sender. Connect the wire coming from the gauge to each sender individually and see which one is causing the problem. Flatheads have two senders because each side of the engine is isolated from the other so coolant mixes in the radiator not the block. I usually take an ohmmeter and test between the terminals and the case as I have found they can short to ground. I don't believe it matters which side of the two prong goes to the gauge as it is just a switch.

wadsjc · 10-12-2011, 02:33 PM

I read somewhere that the gage parks at H and moves down when the ignition is on. That is the way it worked before. Thanks for your reply. I will try hooking the gage to the single contact sender.

rotorwrench · 10-12-2011, 07:43 PM

Usually the twin post switch is on the driver's side or left side of the car and the single terminal sender is on the passenger side (right). This allows for connection from the wire harness that is run on the left side from the firewall to one of the twin posts. The jumper just connects the right sender to the left switch's other terminal post. If the harness exits the firewall on the right side, say on a right hand drive vehicle, then it would be the other way round.

The reason the terminals are staggered on the twin post switch, is to make sure they won't short together. The manuals show the tall one connecting to the indicator wire but I think it would work either way.

Kerby

Cecil/WV · 10-12-2011, 08:18 PM

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Most of the 8BA's that I have seen on the show field has the single post on the left, but my original '50, has the single post on the right and the harness fits real nice that way. I have since rebuilt the engine and installed a new harness, and put it back as it was new. It seems that nothing is standard on these cars.

wadsjc · 10-13-2011, 07:06 PM

I am goimg to test the senders with an ohm meter - post to case. What reading should I get. I assume I don't want continuity.

gearhead1952 · 10-13-2011, 10:49 PM

The single terminal sender may be low ohms but shouldn't be zero or infinite. The two terminal switch sender should have no continuity between either post and the case, should be continuity between the two posts when cold.

rotorwrench · 10-14-2011, 10:14 AM

The single terminal sender doesn't use variable resistance for the indication but is actually a variable current device. It does have a heater coil around a bi-metalic strip so the heater coil should have a resistance value as Gearhead 1952 mentioned. I'm not sure what the average value in Ohms is though if read with a multi-meter. When working, the sender draws less current for the heater as the bi-metalic strip gets warmer so the indicator reads a higher temp as the current required to open the contacts gets to be less and less.

There are several threads about this subject on this board and there should be several illustrations of the circuitry with them if you do a search. The only way I know of to test them is with the system connected using jumper leads and a pot of hot water or oil on a hot plate to generate the heat. Oil won't boil so is a little safer to use than water to heat up a temperature related sending unit.

Kerby

blown49 · 10-14-2011, 12:46 PM

Ther are 4 or 5 prints on the temperature wiring I can e-mail you if you want them. PM me. One basic print is shown in Post #4 of the following thread.

https://fordbarn.com/forum/showthread.php?t=2104

Hope this helps,

Jim

wadsjc · 10-16-2011, 10:03 AM

Jim

Thanks for the print. I ran the test on the 2 pole sender grounding each terminal separately and the gage worked. I tested the connecting wire between senders for continuity and it was good. I then tested the single sender grounding the terminal and the gage worked. Without grounding the terminal(s), the gage does not respond. I could use the preceding page to the print you sent me to and I believe it will tell me the singlepole sender is defective. If you would email me the prints, I would be most appreciative. Thank you

Joel
[email protected]

wadsjc · 10-22-2011, 09:42 AM

Thanks for the pictures Jim

10-12-2011, 11:55 AM	#1
wadsjc Junior Member Join Date: Sep 2011 Posts: 18	1951 Ford F1 Temperature sender There are two temp senders on my flathead V8. The one on the driver's side is a single pole and the crossover wire connects it to the 2 pole sender on the passenger side. The second terminal on the passenger side sender connects to the wiring harness. Does it matter which terminal attaches to the harness? One pole is taller than the other. Thanks in advance for your help.

10-12-2011, 01:53 PM	#2
wadsjc Junior Member Join Date: Sep 2011 Posts: 18	Re: 1951 Ford F1 Temperature sender Some additional information. The temp gage was working OK. I swapped out the starter relay, started the truck and noticed that the temp gage stayed on H - no movement. The coolant is ok and not overheated. The gage just seems to have stopped working. Swapping the two connections to the Dual contact sender doesn't change anything.

10-12-2011, 02:11 PM	#3
gearhead1952 Senior Member Join Date: May 2010 Location: Julesburg, Colorado Posts: 714	Re: 1951 Ford F1 Temperature sender There are two type of senders on the truck flathead. The single wire connection is a normal sending unit. The two wire is actually a switch and opens when engine overheats. So if yours is going to hot instantly with the key on then may have a broken wire or maybe a bad sender. Connect the wire coming from the gauge to each sender individually and see which one is causing the problem. Flatheads have two senders because each side of the engine is isolated from the other so coolant mixes in the radiator not the block. I usually take an ohmmeter and test between the terminals and the case as I have found they can short to ground. I don't believe it matters which side of the two prong goes to the gauge as it is just a switch.

10-12-2011, 07:43 PM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,436	Re: 1951 Ford F1 Temperature sender Usually the twin post switch is on the driver's side or left side of the car and the single terminal sender is on the passenger side (right). This allows for connection from the wire harness that is run on the left side from the firewall to one of the twin posts. The jumper just connects the right sender to the left switch's other terminal post. If the harness exits the firewall on the right side, say on a right hand drive vehicle, then it would be the other way round. The reason the terminals are staggered on the twin post switch, is to make sure they won't short together. The manuals show the tall one connecting to the indicator wire but I think it would work either way. Kerby Last edited by rotorwrench; 10-12-2011 at 07:51 PM.

10-12-2011, 08:18 PM	#6
Cecil/WV Senior Member Join Date: May 2010 Location: Gerrardstown, WV Posts: 2,266	Re: 1951 Ford F1 Temperature sender Sponsored Links (Register now to hide all advertisements) Most of the 8BA's that I have seen on the show field has the single post on the left, but my original '50, has the single post on the right and the harness fits real nice that way. I have since rebuilt the engine and installed a new harness, and put it back as it was new. It seems that nothing is standard on these cars.

10-12-2011, 02:33 PM	#4
wadsjc Junior Member Join Date: Sep 2011 Posts: 18	Re: 1951 Ford F1 Temperature sender I read somewhere that the gage parks at H and moves down when the ignition is on. That is the way it worked before. Thanks for your reply. I will try hooking the gage to the single contact sender.

10-13-2011, 07:06 PM	#7
wadsjc Junior Member Join Date: Sep 2011 Posts: 18	Re: 1951 Ford F1 Temperature sender I am goimg to test the senders with an ohm meter - post to case. What reading should I get. I assume I don't want continuity.

10-13-2011, 10:49 PM	#8
gearhead1952 Senior Member Join Date: May 2010 Location: Julesburg, Colorado Posts: 714	Re: 1951 Ford F1 Temperature sender The single terminal sender may be low ohms but shouldn't be zero or infinite. The two terminal switch sender should have no continuity between either post and the case, should be continuity between the two posts when cold. Last edited by gearhead1952; 10-14-2011 at 08:52 PM. Reason: typo

10-14-2011, 10:14 AM	#9
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,436	Re: 1951 Ford F1 Temperature sender The single terminal sender doesn't use variable resistance for the indication but is actually a variable current device. It does have a heater coil around a bi-metalic strip so the heater coil should have a resistance value as Gearhead 1952 mentioned. I'm not sure what the average value in Ohms is though if read with a multi-meter. When working, the sender draws less current for the heater as the bi-metalic strip gets warmer so the indicator reads a higher temp as the current required to open the contacts gets to be less and less. There are several threads about this subject on this board and there should be several illustrations of the circuitry with them if you do a search. The only way I know of to test them is with the system connected using jumper leads and a pot of hot water or oil on a hot plate to generate the heat. Oil won't boil so is a little safer to use than water to heat up a temperature related sending unit. Kerby Last edited by rotorwrench; 10-14-2011 at 10:20 AM.

10-14-2011, 12:46 PM	#10
blown49 Senior Member Join Date: May 2010 Location: West Union, Ohio Posts: 113	Re: 1951 Ford F1 Temperature sender Ther are 4 or 5 prints on the temperature wiring I can e-mail you if you want them. PM me. One basic print is shown in Post #4 of the following thread. https://fordbarn.com/forum/showthread.php?t=2104 Hope this helps, Jim __________________ Visit my Blown '49 Merc website @ http://www.blown49.com

10-16-2011, 10:03 AM	#11
wadsjc Junior Member Join Date: Sep 2011 Posts: 18	Re: 1951 Ford F1 Temperature sender Jim Thanks for the print. I ran the test on the 2 pole sender grounding each terminal separately and the gage worked. I tested the connecting wire between senders for continuity and it was good. I then tested the single sender grounding the terminal and the gage worked. Without grounding the terminal(s), the gage does not respond. I could use the preceding page to the print you sent me to and I believe it will tell me the singlepole sender is defective. If you would email me the prints, I would be most appreciative. Thank you Joel [email protected]

10-22-2011, 09:42 AM	#12
wadsjc Junior Member Join Date: Sep 2011 Posts: 18	Re: 1951 Ford F1 Temperature sender Thanks for the pictures Jim