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Posted By Discussion Topic: Temperature Sending Units-1951 V-8 Ford Custom -- page: 1 2     Jules51 05-17-2020 @ 9:30 AM reply profile send p.m. Member Posts: 58 Joined: Jul 2015 Which side, Driver - Passenger - does the single prong temperature sending unit go? Part # 8A-10884. I understand that this is the primary. If I have it reversed; double prong, #8A-10990, on Driver side, will this give me a incorrect reading on my temp gauge? Temp gauge reads Cold while driving but when I'm parked idling it moves to the center and once I start driving it falls back to Cold., with engine OFF, the needle moves to HOT, which is correct. Thermostats are good, IR temp reading of radiator is normal, temp gauge is ok, wiring is correct. What am I missing? Thanks Jules51 51woodie 05-17-2020 @ 10:12 AM reply profile send p.m. Senior Posts: 509 Joined: Jan 2017 Not real familiar with the '51, but my'46 has the single contact on the passengers side, a connecting wire goes to one terminal of the double contact on the drivers side, and the temp gauge wire is connected to the other terminal. The single contact unit is what sends the temp signal to the gauge. The double contact sender is like an on/off switch, which opens when the temp on the drivers side gets too high, which causes the gauge to go to full hot. JayChicago 05-17-2020 @ 11:58 AM reply profile send p.m. Member Posts: 471 Joined: Jan 2016 Does not matter which side has the switch vs. the sensor/sender. When you say gauge is reading cold, do you mean it is at the bottom of the gauge scale, or do you just mean it is in the lower portion of the scale? If you have 160 degree thermostats, it may be reading correctly in the lower part of the gauge scale. Your symptom: "Temp gauge reads Cold while driving but when I'm parked idling it moves to the center and once I start driving it falls back to Cold." That makes me think of a thermostat remaining open, on the sensor side. Are you sure the thermostat is good? You said you read the temp of radiator with an IR thermometer, but did you read temps on the heads / hose fittings near the thermostats? You could do that and compare side to side. Another thought: the sender could be inaccurate, only moving the needle when engine temp gets warmer at idle. Jules51 05-17-2020 @ 12:30 PM reply profile send p.m. Member Posts: 58 Joined: Jul 2015 Jay, thanks for your response. When I read the temp with the IR, I was getting an even reading of about 170-175 across the heads. Thermostats were replaced, 160 rating and appears to be functioning. The needle goes to the bottom of the C but I do get a little movement at stop lights, then back to C. Question: the wire from the main harness for the sender, I'm connected to the double on the driver side then using the x-over wire to the single head on the passenger side; refer to pic. Thanks Jules51 51woodie 05-17-2020 @ 3:45 PM reply profile send p.m. Senior Posts: 509 Joined: Jan 2017 Here is the wiring diagram for the senders, and the routing for the connections. I guess it doesn't matter which side the senders are in, as long as they are connected as shown. This message was edited by 51woodie on 5-17-20 @ 3:47 PM JayChicago 05-17-2020 @ 8:01 PM reply profile send p.m. Member Posts: 471 Joined: Jan 2016 Jules Your two senders and the wire routing is correct. And your temperature readings on the heads seem right for 160 degree stats. I'm at a loss to understand why your gauge would behave that way. The only thing I can suggest is you try replacing the single pole temp sender with another to see what happens. That sender is the one that varies with temperature to vary the gauge's needle position. Perhaps that sender is faulty. Perhaps it is providing a correct value at warm temp when engine idling, but then it incorrectly jumps all the way to cold when the engine cools slightly as you drive. (If that sender is a new aftermarket sender, replace it anyway. Electrical items like this can sometimes be bad right out the box) Jules51 05-18-2020 @ 5:02 AM reply profile send p.m. Member Posts: 58 Joined: Jul 2015 Thanks for the additional information and diagram, this will help. Thanks Jules51 TomO 05-18-2020 @ 8:11 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 Jules51, the single terminal sender is supposed to indicate the temperature and the double contact sender is just a overheating switch that opens when the engine is overheating. You have yours wired correctly. T Your single terminal sender is probably one of the recent aftermarket types. They seem to fail in the manner that you describe, reading low and slow to react to temperature changes. The best ones have KS stamped on the side. These are the original King Seeley units and are becoming very hard to find. Change yours with a new one or a good used one with the KS stamped on the side. Look for a replacement at swap meets. Tom Jules51 05-18-2020 @ 1:39 PM reply profile send p.m. Member Posts: 58 Joined: Jul 2015 Tom, thanks for the information. I've learned something today, the KS units. I've searched my spare parts and DID find a KS unit, stamped a circled KS and has the number 224 stamped on the opposite side. It's clean. Is there a way to test these units? Thanks Jules51 Jules51 05-18-2020 @ 1:44 PM reply profile send p.m. Member Posts: 58 Joined: Jul 2015 Tom, an update: I have the Thermal Unit also, same KS stamp but has the # 217 stamped. Thanks Jules51

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