I bought a Repro Temp sending Unit From Dennis Carpenter. B6C-10884-A. Not keeping constant setting. Has anyone else had a problem with One of His senders? I would have preferred NOS but impossible to find. Thanks!

  

I bought one a couple of years ago and had the same issue. No reading and then suddenly it would come good. I think the issue is that it is a B6C 10884 without the A on the end. I suspect that it is fine for a light but no good for a gauge. They do come up NOS on Ebay occassionally. I bought one to replace that unit and also bought a spare about a week ago. There's one there now but it's very expensive.

My experience has been that the gauge & sending unit should be a matched set. 

When I converted my dad's (now mine) 55 Tbird to 12v, I retained the original gauges and sending units. Although I question the accuracy of the original gauges, I saw no appreciable difference in their accuracy once I converted to 12v. I have since bought Autometer electric temperature, oil pressure, and voltage gauges and sending units, but the original gauges will be retained as well. 

When I sent my B intake manifold to Ted Eaton for porting, he also drilled and tapped it, just to the right of the thermostat cavity, for a temperature sensor, having said that the location provides a more accurate reading that the location at the rear of the driver's-side head. I later drilled & tapped my Mummert intake in the same location for the Autometer sending unit.  

I have a mechanical Temp gauge in the front of Manifold next to thermostat housing. it works fine. the original dash gauge has always worked fine until i took engine apart last fall. now The Sending Unit that was working fine quit. Bought a Dennis Carpenter replacement  which seems to be the only one available no matter where You buy it. Not working consistently

  

There is only One sending Unit used for 56 Cars and Trucks for a Gauge only. No Lights were ever used for Temperature.B6C-10884 or B6C-10884-A are same application. Finding an original is hard and right now the only one on Ebay is not in my price range.

  

The orig. sending units (& gauges?) tend to read high eventually. NOS replacement brought the needle back to center.  More reasonably priced units may turn up eventually. Just check ePay regularly.

6 VOLTS/POS. GRD. NW INDIANA

If it was working before you took the engine apart, but is not now, could it be a wiring issue? Maybe you accidentally stripped a wire or crushed it? Just a thought.

The Power Feed Wire from Ignition Switch is fine. Ground is controlled by Wire to sending Unit. Varies as heat changes. Either Sender or Gauge not working properly. I have tried I original Sender and replacement Sender. Neither works properly.  have another Gauge that was in a complete Dash I bought for $100. I just tested it with 12 volts and ground Wires and surprisingly it goes to "C" as it should. Going to install it and see if it works correctly with original Sender. These Gauges are pretty durable as they are the only Ones Ford ever made to work on 12 Volts. After 56 they had a step down device so they worked on 6 Volts even though cars were 12 Volt. Let U know if replacement Gauge works. This Dash I bought was one of the Rarer Padded Dashes so I have the various Trim Pieces used to trim the Dash Pad. Hard to find Parts. Gauges were a bonus.

  

"I bought one a couple of years ago and had the same issue. No reading and then suddenly it would come good. I think the issue is that it is a B6C 10884 without the A on the end."

Many vendors use partial FORD PN's to make one think the part is GENUINE FORD. They can only show/use a partial PN as to copyright liability. The correct FORD P&A PART NUMBER is B6C 10884-A

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I would much rather have an original NOS one but virtually impossible to find at reasonable Price. I find a lot of repro electrical Items DON'T work as originals did.