Temperature Sending Unit Question

19Fordy

19Fordy

Well-known member
Would any damage be done to the temp. gauge if the two- pronged sender on
the driver side head was replaced with a single pronged terminal temp. sender
(like the one on the pass. side head) and the wire on the pass. side sender then
connected to the newly installed single pronged sender on the driver side along with the wire to the gauge? (Gosh, that's a long sentence.)

I realize the 2 pronged sender unit acts as a switch and am wondering if it's really needed.
Engine is 8BA. Thanks, Jim
 
Kurt, Please explain what you by "Possibly- and it wouldn't work."
I am not understanding your reply.
 
Based on my understanding of how the King-Seeley system works, if you do what I think you are proposing, you will overload the receiving bi-metallic strip with the input from the two bi-metallic strips in the senders, causing the gauge to read double the actual reading until something goes POOF!

Not a good idea. You could put them on a switch that you could manually throw to read the alternate senders, though.
 
The current flowing through the gauge unit would most likely be constant because it is carrying twice the load, not enough to open the contacts in the senders, it’s not a resistance system, the senders have contacts in them and heaters, both heaters on at the same time would overheat the gauge unit, how long it would tolerate it I don’t know.
In any case the gauge would not be accurate unless a switch is used to change left-right as was mentioned.
With the original system you know the temperature of one side ( single terminal) and you can tell if the other side overheated by the sudden movement all the way when the 2 terminal side overheated.
 
Terry said:
Damage no, proper reading no. Just install one single terminal unit.
Click to expand...

You're probably right, but I wouldn't take the chance. The smoke that powers the electrical systems can get out at the strangest times and the only known replacement is by Lucas, and you know what that means.:D

It is the proper polarity, though.:rolleyes:
 

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THANK YOU all for answering my request for an explanation. I now understand. My 2 pole sending unit (switch) doesn't open up when the engine warms up so perhaps I'll take it apart as Tubman explained in one of his earlier posts.
 
19Fordy said:
THANK YOU My 2 pole sending unit (switch) doesn't open up when the engine warms...
Click to expand...
The switch should only open when engine gets very hot. (then gauge needle goes to full-hot position) Under normal warm operating temps, switch stays closed to carry gauge control circuit over to the passenger side sender, which is controlling the gauge.
 
Thank you Jay. Prior to this I the sender would have continuity until the engine got to about 200 degrees and the points in the sender would open and continuity broken.
 
I'm confused given the responses here. Half a dozen years ago I did what 19Forty asks about. I installed a mechanical temperature gauge system on the passenger side and moved the passenger side OE sensor to the drivers side head. When at running, the gauge has and does register as it did before. There was a popular issue with the stock OE set up where during warm-up, the dash gauge would "spike" up to hot for a minute and then drop down to running temp. My mechanical sensor/gauge behaves correctly. My current OE sensor still spikes but I'm not bothered by it.
 
It was my understanding that the O/P wanted to run two stock senders hooked up to the same stock gauge. I have done what you have done : one stock sender to one stock gauge and one mechanical sender to one mechanical gauge. The first approach won't work, the second will.

Oddly enough, on my car at least, the stock gauge responds faster than the mechanical gauge.
 
tubman: I think there's a historical net concusses among many that suggests that each side of the block may heat up at a different rate due to differences in the block casting. Other factors could be having a heater circuit connected to (usually) the passenger side which increases the volume of coolant on that side, or the temperature rating of the thermostats installed. Regardless when the coolant gets warmed, mixed-up in the radiator (some does bypass the thermostats) and circulates around the block, that dash gauge is showing an "average" that passes by the sensors.
 
What I observe is that on startup, the stock gauge will read 140 degrees while the mechanical is still at 100. It catches up eventually and both even out at 180 (the thermostats that are used).
 
tubman: Your dash gauge reads 140 degrees at start up (?) I'm not familiar with your model but is that the bottom # of the gauge dial ? Otherwise it would indicate the gauge is malfunctioning.
 
No. They both start at the bottom (whatever that is) when the engine is started. The stock gauge gets to about 140 at the same time the mechanical hits 100. when fully warmed up, they both read 170-180. The stock gauge reacts quicker to the increase in engine temperature, which initially was counter-intuitive to me. When I thought about it, electricity is probably a lot faster that heat conduction through a fluid.
 
The flathead V8 has two separate cooling systems in the block that share a common radiator. The first (two terminal) sender in the line is an emergency on type sender that only activates at the set overtemp temperature. The second one with the single terminal is the one that approximates the temperature in the right bank of cylinders. If a person experiences a very rapid HOT reading then it would be the left bank. If it slowly rises to the overtemp level then it would be from the right bank but truthfully, if either bank overheats then it will bring the whole radiator up to overtemp eventually. Most folks don't watch their dash indicators well enough to notice when the thing started to overheat or how fast it went into overtemp but they will see the steam coming from under the hood if nothing else.

The King Sealey system indicates full HOT when the power is turned off. It drops to COLD when the key is first turned on for the day. It is based on a current pulse operation where the frequency of the pulse rate of the opening and closing bi-metallic breaker changes as the temperature increases. The indicator gauges are calibrated to read the current level that is reaching it. The coolant temp, oil pressure, and fuel quantity all work on this same principal.
 
Here is a schematic for the temp sensors. Ford designed their gauges to be "Fail Safe", in that if the oil, temp or fuel gauge circuits became disconnected, the oil would go to "0", the temp would go to "H" and the fuel would go to "0".
If you bypass the dual terminal sender, your gauge will work, but it will only indicate the right bank temperature
 

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I wonder if it would be possible to rebuild the 2 pole temperature sending unit. I carefully cut away the top and pulled out the inside temp unit BUT, I am not sure how it can be checked to see what needs fixing.
 
"51woodie" provided a pretty good depiction of the "switch" unit in the post above yours. I would check it to see that the points aren't welded together; Try to separate them if they are and if they're not, dress them with a points file. Then test it in a pot of boiling water. You may have to carefully bend the arm(s) to get them into proper alinement.
 
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