I have a '52 8BA flathead that was converted to a 12 volt system by the previous owner. Most everything is 12 volt with the exception of some original stuff like the fuel tank sender unit which is wired to a 12 volt - 6 volt reducer. The Temp sensor on the right side of the engine is an original sensor (Sensor 224 with a single screw) and is connected to the original temp guage and seems to work fine. The sensor on the left side is an aftermarket sensor hooked up to an aftermarket temp guage, which never worked since I got the truck.

I have a few questions:

1. The flathead has a sensor on both sides of the motor. If one is hooked up to the temp guage, what was the other side hooked up to?

2. Why are the two original sensors different? The one on the right (#224) has a single screw, and the one on the left (#217) has two screws.

3. I assume the original sensors were for a 6 volt system, yet mine has been converted to 12 and my original guage seems to work fine. Do these sensors work for either 6 or 12 volt systems, or is there something else happening that I'm just not realizing? I mean the wire seems to go directly from the sensor to the guage........or does it???

4. Lastly, I would love to get the old (or a new) aftermarket guage to work. Would the orignal sensor (#217) work? As far as I can tell the connection goes directly from the guage to the sensor. I just don't understand how to reconcile the 6 volt 12 volt thing.

Electrical work is certainly not my specialty, so any help or advice would certainly be appreciated

 

I'm not the best on electrical stuff but I manage to muddle my way around it.

The original sensor single post is an actual variated sender and tells the original gauge what's going on in that head.

The 2 post sender is simply a bi-metal panic switch. If the coolant temp exceeds a preset level, the sender opens and the gauge goes instantly HOT. The wire from the gauge goes to one post of this sender. A jumper wire goes from the other post to the single post sender.

The senders only see 6V. You should have a voltage regulator for your gauges. The voltage should be stepped down there before it gets to the sender.

I can't help with your aftermarket setup, but it should be similar to the single post sender. Gauges and senders are usually a set - it could be the sender is bad.

 

Joe, If you need any NON electrical help...let me know...I'm also in HH...top of the hill...south of the power poles.

 

Yes one wire goes from one sending unit to the other then to the gauge. That way you dont have to run two gauges one for each head.

 

Since the temp senders basically work by varying the ground, you should have a voltage reducer on the hot wire to the gauge like mtflat mentioned. The other post on the gauge is the wire to the temp senders, so the volt reduction takes place and the temp senders see same 6 volts they've always seen. BE SURE you have a reducer on the gauge, as it may work for a little while but will eventually burn out the gauge.

There single post sender should have a wire to one of the posts on the two post sender, and the other post of the two post sender is what goes to the gauge. The gauge reading you get may not be extremely accurate, but it will be enough that you know if you are overheating. The gauge can be adjusted I found out -- I bought a NOS gauge and it kept indicating overheating, but a cheapie aftermarket gauge I dropped in the radiator was quite the opposite. I was able to calibrate the NOS one with the one in the radiator, so I have a pretty good idea of what the temp on my dash gauge really is.

 

Thanks to everyone for the info, but I have another question, and excuse me if it seems dumb. Under the original 6 volt system, we have a wire from the single terminal sensor to the double terminal sensor, and then a wire from the double terminal sensor to the guage itself. Is there then another wire from the guage to a power source (like the ignition switch)? If I am correct with this assumption under a 6 volt system, to make this compatable with a 12 volt system, that power wire should lead to a the voltage reducer panel under my dash, just like the wire from the fuel tank sender, right? Forgive me, but I'm feeling my way through this, and you guys have been great on more than one occasion.

 

Yep, you've got it. Power to ignition switch, then to the voltage regulator(reducer) and then to the gauge.

Some guys go to the expense of installing Runtz brand resistors on each gauge, but you can accomplish the same thing by using 1 voltage regulator for all the gauges. Just put it in the power line before the gauge cluster. Echlin IR1 at NAPA I believe.

 

This should make it clear

 

ALBUQ F-1, that old sevice buletin diagram was excellent. Thanks! Now, you wouldn't have anything similar for the oil pressure guage would you? I'd love to get that factory guage working too!

Thanks again