| Pair of 40's | -- 11-05-2010 @ 6:47 AM |
|
40 deluxe, I have a radiator aux fan running thru a thermostat on the pass side head. I have a single bulb temp sending unit in the driverside head. The gauge goes to the cold side. Any suggestions?
|
|
| supereal | -- 11-05-2010 @ 7:52 AM |
|
Remove the wire from the sender. If the gauge swings over to the "hot" side, the gauge and wiring is OK. Going to the "cold" side usually indicates a short to ground, either in the wiring, or the sender. The first test should confirm if the wiring and gauge is OK. If you are trying to run the 6 volt gauge on 12 volts, you will need a voltage dropper for the gauges. I mention this because most aux. fans are 12 volts. Continuing to run the gauge on 12 volts, if that is the case, will likely result in destruction of the bimetal element that swings the needle.
|
|
| Pair of 40's | -- 11-05-2010 @ 8:24 AM |
|
Thanks, car is still 6 volt, fan will run if it gets over 190. Gauge gos to hot with switch off. I had a two post sending unit but that also would not read if hooked just to driver side. We wired gauge per the ford diagram. Not sure where a ground problem would exsist?
|
|
| supereal | -- 11-05-2010 @ 10:53 AM |
|
The two terminal sender is just a "fail safe" switch that opens at or near the boiling point. This sends the gauge to the hot side, as it, in effect, disconnects the gauge from both senders. Shorting the wire that leads to the gauge to ground should send the needle to the cold side. The gauge receives power from the acc side of the ignition switch, and "looks" for ground thru the sender. From your description, it appears that the body of the sender is making contact with the head, so my best guess is that the sender, inself, is defective. The original equipment sender has a heating element in it that sets the bimetal points. If this element is faulty, the reading will be false. The contacts in the sender actually buzz. As the ambient heat increases, the buzzing rate falls, allowing the needle to register more hot. Your best way to determine whether the sender is bad is to substitute a known good one after being sure the wiring is not the problem, as the design of the sender makes testing with an ohmmeter inconclusive. This message was edited by supereal on 11-5-10 @ 10:59 AM
|
|
| Pair of 40's | -- 11-05-2010 @ 2:36 PM |
|
Ok, I have a brand new double sending unit. Can this be used for just one head? Thanks again for your time, I'm learning.
|
|
| Stroker | -- 11-05-2010 @ 3:11 PM |
|
Super: That double terminal "fail safe" sender puzzles me. We had Ford trucks with a double terminal tar-filled disconnect in one head. This would interrupt the ignition primary, but could be "reset" by inverting for a time in a pan of boiling water. Do you know if this was just a truck item, or did they ever find their way into automobiles? The trucks that these were installed on were a 40 ton-and-a-half, a 41 dump truck, and a 42 dump truck. Dan
|
|
| TomO | -- 11-05-2010 @ 4:57 PM |
|
Pair of 40's, The double connection sending unit is just a switch that opens when the temperature of the coolant reaches boiling point. It will not give any indication of temperature change. Tom
|
|
| Pair of 40's | -- 11-06-2010 @ 8:24 AM |
|
I was under the impression that the double sending unit was for the gauge to read off both heads, gauge wire to one pole and the 2nd pole wire across to the 2nd head?
|
|
| TomO | -- 11-06-2010 @ 8:38 AM |
|
The single terminal sending unit has a bi-metal strip that is heated by the engine coolant. As it is heated, it bends to open the gap of the contact points in the sending unit. This reduces the current flowing in the circuit to the gauge and causes the needle to move towards the hot side of the gauge. The double contact sending unit is just a fail safe as it opens the circuit when the temperature reaches boiling point. If it had the same circuit as the single terminal unit, either the gauge or the sending units would have to be matched for the double sending unit installation. The normal positions when using 2 sending units is the single terminal unit is in the right head and the double terminal unit in the left head. When only 1 sending unit is used, it must be the single terminal unit and it would be installed in the left head. I hope that I have cleared it up for you. Tom
|
|
| supereal | -- 11-06-2010 @ 10:17 AM |
|
The two terminal sender, as pointed out, opens when the temperature approaches boiling, and should reset itself when it cools down. The wire between the senders should be carefully checked and tested with an ohmmeter. Finding them, or their teminals, frayed or broken is not unusual. These senders can be installed in either head. They are usually positioned as Tom points out. Original used or NOS senders are rare and pricey, and I have little faith that the repros are reliable, if they work at all.
|
|
| Pair of 40's | -- 11-06-2010 @ 10:38 AM |
|
Thanks for your advice!
|
|
| Old Henry | -- 11-06-2010 @ 12:55 PM |
|
Sometimes a picture is worth at least 100 words (or is it 1000. I never get that straight.) Anyway, here's a wiring diagram that shows the current passing through the temeperature gauge, then THROUGH the left sensor on the engine block over to the right sensor where it is controlled by the temperature there as it is grounded completing the circuit. (I've circled the two sensors on the block.) When the left sensor trips, it cuts off all current flow to the right sensor and ground sending the gauge to max just as when the key is off. Still Old Henry
|
|
| EFV-8 Club Forum : | https://www.earlyfordv8.org/forum |
| Topic: | https://www.earlyfordv8.org/forum/viewmessages.cfm?Forum=18&Topic=2131 |