I stumbled across some flathead temeprature sending units and I am trying to figure out how to test them to see if they are any good. If it matters they are out of 8BA's and I pulled them out of a junk yard. Have any ideas? Yo' help is appreciated. Thanks.
Pan with hot water ,termondator and ohm meter.Havee lot of removed stock ones will give to you. Sad icon is about henry j guy bummed.
Some engines ran TWO temp sending units. One on either head. One side had one terminal, the other had two terminals. If you can "jury rig" a temp gauge with a battery and hook them up (the sending unit with the single terminal hooks to the sending unit with the two terminals) and as yorg said, "put them in some boiling water." You should be able see if they are still working. Someone on here might be able to "jump in" and give you the "resistance measurements." For both "hot" and "cold." They were made fairly tough, and other than being physically damaged, most of them are still working.
I am good with the "put in hot water" thing, it makes perfect sense. Especially with a thermostat. I think I have a temp gauge flying around that I could use also. I guess I am getting confused since they are monitored off of an electric system and I am confused on how I should set this up. I am thinking that if I use a temp guage and supply it power while the sending units are in hot water I should be able to get a reading. Would the ohm rating on my aftermarket gauge and the sending unit rating differ? Trying to figure this out is blowing my mind, man. I am stuck on the sender changing the ohm reading that would make the gauge go this-a-way or that-a-way...I am so confused...
I don't know what the readings should be on a stock sending unit, but the way I check mine is with an ohmmeter and some hot water. The sending units work by changing the resistance across themselves as temperature increases, so you should a noticeable change in resistance as they warm up.
On the dual-terminal sender units, it's just a switch - there will be no resistance change. I believe it closes when heated (around 200*) allowing the reading to be taken from the single-terminal sender in the circuit...
[ QUOTE ] On the dual-terminal sender units, it's just a switch - there will be no resistance change. I believe it closes when heated (around 200*) allowing the reading to be taken from the single-terminal sender in the circuit... [/ QUOTE ] If you are correct, wouldn't the temp gauge read cold until the water reached 200F?
Today's reading from the good book: Left unit (2 terminals) is essentially an idiot light switch: normally closed, opens at boiling cutting off the circuit and pegging the gauge. Right one with single post works the gauge otherwise, the smaller the current the higher the gauge reading. I say puttem in the car and see if they work. Most original ones are OK. I have heard the repros give very random reults. Flatdog, how's the project going? I've dragged all my supercharger books together and need to bring them over. Bruce
Darn it Bruce, you type faster than I do!! [ QUOTE ] [ QUOTE ] On the dual-terminal sender units, it's just a switch - there will be no resistance change. I believe it closes when heated (around 200*) allowing the reading to be taken from the single-terminal sender in the circuit... [/ QUOTE ] If you are correct, wouldn't the temp gauge read cold until the water reached 200F? [/ QUOTE ] Ernie, now you have me wondering; maybe Flatdog could take a two terminal temp sending unit and put an ohmmeter across the two terminals. If it is a switch, then when it's cold, it should read ZERO. Then if he heated it up, (200 deg.; some boiling water) it should read read FULL scale. i.e. NO resistance. I was always lead to believe that the two sending units hooked together would produce "X" impedance either hot OR cold and Ford used gauges to reflect the change. Any flatheads I have built, used aftermarket gauges and senders, so I can't speak with experience. Just went scrounging and can't get to a couple of heads that still have original sending units in them.
[ QUOTE ] Today's reading from the good book: Left unit (2 terminals) is essentially an idiot light switch: normally closed, opens at boiling cutting off the circuit and pegging the gauge. Right one with single post works the gauge otherwise, the smaller the current the higher the gauge reading. [/ QUOTE ] Son of a gun! I just learned something NEW today. That would explain why I have seen some flatties with just the one sending unit (single terminal) and a stock gauge. Thanks Bruce and Ernie.
[ QUOTE ] normally closed, opens at boiling cutting off the circuit and pegging the gauge. [/ QUOTE ] Am I on a run or what? That's twice in two days I've gotten it ass-backwards! Been one of those years! Still - I don't think you can use one of these senders with a normal gauge (read: modern) - they're meant to be used with the old Ford bi-metallic gauges (although I can't speak with certainty about the later model ones...)
[ QUOTE ] [ QUOTE ] normally closed, opens at boiling cutting off the circuit and pegging the gauge. [/ QUOTE ] Am I on a run or what? That's twice in two days I've gotten it ass-backwards! [/ QUOTE ] Ahh well Ernie, now we both are a bit smarter!!!
[ QUOTE ] Ahh well Ernie, now we both are a bit smarter!!! [/ QUOTE ] Smarter maybe, wiser? Not me! Anyone ever heard of the penguin theory? Your brain is like an iceberg floating in the ocean & your brain cells are like penguins sitting on the iceberg. You can only fit so many penguins on the iceberg at any one time. If you put on one more than it holds, one will fall off from somewhere near the edge. Occasionally, if you try hard, you can put a bunch of penguins on each others shoulders (like when you cram for an exam), but this is short-lived & can hurt the penguins below. In the end, you're still left with just the basic penguins one-deep. All too often, though, a small (hopefully) part of the iceberg cracks off & you lose the penguins that were on that part. I think the penguin that knew about sending units fell off a while ago...
Oh boy, now you started it.... Dead Duck...... (not quite related to temperature sending units, but.........!!) A woman brought a very limp duck into a veterinarian's office. As she lay her pet on the table, the vet pulled out his stethoscope and listened to the bird's chest. After a moment or two, the vet shook his head sadly and said, "I'm so sorry, Cuddles has passed away." The distressed owner wailed, "Are you sure? "Yes, I am sure. The duck is dead", he replied. "How can you be so sure," she protested. "I mean, you haven't done any testing on him or anything. He might just be in a coma or something." The vet rolled his eyes, turned around and left the room, and returned a few moments later with a black Labrador Retriever. The duck's owner looked on in amazement as the dog stood on his hind legs, put his front paws on the examination table and sniffed the duck from top to bottom. He then looked at the vet with sad eyes and shook his head. The vet patted the dog and took it out, and returned a few moments later with a beautiful cat. The cat jumped up on the table and also sniffed delicately at the bird. The cat sat back on its haunches, shook its head, meowed softly and strolled out of the room. The vet looked at the woman and said, "I'm sorry, but as I said, this is most definitely, 100% certifiably, a dead duck." Then the vet turned to his computer terminal, hit a few keys and produced a bill which he handed to the woman. The duck's owner, still in shock, took the bill. "$150!" she cried, "$150 just to tell me my duck is dead?!!" The vet shrugged. "I'm sorry. If you'd have taken my word for it, the bill would have been $20, but what with the Lab Report and the Cat Scan........
Here is my main reason for pulling the senders from the yard to begin with. When I first start the car, the temp gauge will read at about the mid range. Totally impossible as the car has just started. Within a few seconds, more like two or three, the needle is pegged on the high side of the gauge. It is the stock temp gauge and has done this since I bought the car. I re-wired and used voltage resistors and the temp gauge, as well as the fuel gauge, still react the same way. It would be great to have gauges that work and after reading some of the replies it seems like the stock senders are pretty tough. Maybe it's the gauge itself. What I would like to do is go with two seperate temp gauges, one for each head. I need to do some more research...
Okay, I'll dig out the diagnostic stuff from Ford. If you want two Ford gauges, however, what you need is two of the single post senders--then you can just wire them both to your original gauge with a two way switch. FlatDog--Looks like you just skipped your planned 14 second project and went on to start a 13 sec quest--not too bad there!!
[ QUOTE ] Here is my main reason for pulling the senders from the yard to begin with. When I first start the car, the temp gauge will read at about the mid range. Totally impossible as the car has just started. Within a few seconds, more like two or three, the needle is pegged on the high side of the gauge. It is the stock temp gauge and has done this since I bought the car. I re-wired and used voltage resistors and the temp gauge, as well as the fuel gauge, still react the same way. It would be great to have gauges that work and after reading some of the replies it seems like the stock senders are pretty tough. Maybe it's the gauge itself. What I would like to do is go with two seperate temp gauges, one for each head. I need to do some more research... [/ QUOTE ] Just out of curiousity, did you change to 12 volt? You mention resistor. Did you change the new electrical system to NEGATIVE ground? (as opposed to the original 6 volt POSITIVE ground) If you are using the original gauge(s) and sending unit(s); the connections on the gauge would need to be reversed. (the sending unit wire would go to the original "power" connection; and the power to the "sending unit" terminal.
Starting to sound like problem is sender. first, disconnect gauge from wire to engine--it should remain at hot. Next, run your wire from ONLY the single post sender--you don't need to worry about the double one until the main one is known to work, so get it and any problems it may have out of the circuit. Wiring of course cannot be broken or grounded, but you likely have new wire and are pretty sure wire is OK.
Then with two pole sender out of loop and gauge at its running behavior, first ground terminal of remaining sender--gauge should go cold. Disconnect wire and it should go hot. If so and if I am still thinking straight on notenoughcoffeeeee sender is bad. One final problem area--is there teflon or something in joint? If so, retest that sender with a ground wire clipped to its outer shell--teflon can screw up the ground. Do the ground test back to battery, in case something larger is partially isolated. Two pole sender can be tested with continuity light and boiling coffee. Lots of coffee necessary for elecrical problem.
One thing to understand about the Ford gauges is that they work from A bimetal spring being heated by the sending units. Not by resistance change as modern type gauges. here is a picture of the tank units ( im still looking for the Temp unit pics im sure i have it someware. The single pronge one is the Bimetal type and the two prong one is shorting out when hot, making the gauge go Hot
[ QUOTE ] One thing to understand about the Ford gauges is that they work from A bimetal spring being heated by the sending units. Not by resistance change as modern type gauges. [/ QUOTE ] And because of that, you don't need to worry about polarity when you switch to positive ground on any of the gauges except the ammeter.
[ QUOTE ] [ QUOTE ] One thing to understand about the Ford gauges is that they work from A bimetal spring being heated by the sending units. Not by resistance change as modern type gauges. [/ QUOTE ] And because of that, you don't need to worry about polarity when you switch to positive ground on any of the gauges except the ammeter. [/ QUOTE ] Well, it was a thought! Anyway; your back on a roll; and I'm a little "smarter" (or was that wiser?) Here's hoping neither the sending unit(s) or the gauge are a "dead duck!"
[ QUOTE ] Here's hoping neither the sending unit(s) or the gauge are a "dead duck!" [/ QUOTE ] And that all of our penguins have good balance... ...unfortunately, I think my iceberg is floating towards the tropics & there's a pod of killer whales circling it!
After all is said and done... Think this thread deserves to be placed in the TECH-O Matic section. It's a good one for reference.
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