Temp gauge question

[tcom]

I just purchased a '46 Super Deluxe convertible. I'm new to Fords but have owned and restored a couple of prewar CAdillacs, a post war Packard and Chrysler New Yorker.

Question I have is my temp gauge registers a couple of needle widths to the right of center operating in an ambient temperature of 65*. When I temped the coolant in the radiator it was 165*. I parked it in the shop and set the throttle to around 1500rpm and let it run. Highest the temp got was 178* and the needle on the gauge was about a width to the left of hot. I'm not worried about overheating it at this time.

It has a single single wire senser on the passenger side head. The port on the other side has the heater hose mounted. I may be mistaken but weren't there two sensers used on those engines, one a single wire and the other a two wire switch.

There is no evidence that I can find where wires on the drivers side have been cut off.

Is this going to be a simple matter of replacing the senser on the passengers side?


Thanks.

tony

[JayChicago]

Originally Posted by tcom

weren't there two sensers used on those engines, one a single wire and the other a two wire switch. Is this going to be a simple matter of replacing the senser on the passengers side?

A gauge can only take orders from one sender. The pass-thru switch didn't do anything to modulate the gauge. You don't need it.
Your gauge may be reading high due to poor continuity thru the sender. Maybe someone used pipe thread tape. I would remove the sender and clean the threads, and clean the wire connection too.
If that doesn't do anything, replace the sender. Aftermarket senders are available. I don't know how accurate they are.

[tcom]

Thanks Jay.

I cleaned the threads on the sender and chased the threads in the head. There was no change. THe senders are avaiable for around fifty bucks.

I was curious about the two wire switch as they are also available.

tony

[19Fordy]

Try to find original Ford senders as the after market senders are not as good -low quality.

[Ggmac]

The 2 wire sender is simply an on off switch. It would connect to the other sender and the wire currently on the single sender would go to the other terminal on the 2 sender .

[Kube]

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The right-side cylinder head SHOULD have two threaded ports. One for the sending unit, the other for an optional heater (valve). Makes me wonder if you have an incorrect head on that side.
Do seek a NOS (Ford OEM) sending unit. As has been advised in an earlier post, the repops are poopy.

[tcom]

The right head has two ports. The one in the front has the single wire senser. THe rear which is hard to see and I missed when I first looked has the two wire switch. THe wiring harness is new and both leads for the switch come from the harness.

I cleaned and chased the threads on the single wire senser. Next step is to do the same with the switch. THe leads look a little crusty.

THe drivers side head also has two ports with the heater hose plumbed to the rear port. It doesn't look dealership or factory. It has a worm drive clamp on it, the only incorrect clamp in the engine compartment.

Much as I hate to do it, I'm probably going to take the First quarter of the 21st century approach and fire the parts cannon with both sensers or consider it a feature as I have correlated the needle positions with the coolant temps. and not a defect.

tony

[tubman]

Originally Posted by tcom

The right head has two ports. The one in the front has the single wire senser. The rear which is hard to see and I missed when I first looked has the two wire switch. THe wiring harness is new and both leads for the switch come from the harness.

tony

I've seen a lot of stock flathead Fords and I have NEVER seen this. I've read what you have written several times and have come to the inescapable conclusion you are saying that both temperature sensors are in the same head. That makes no sense and will never work. Either I am seriously misreading what you are saying or someone has seriously miswired your car. Every one I have seen has the single terminal sensor in the front port of the right head and the double terminal sensor in the front port on the left head. There is a jumper between the two senders and the wire to the gauge is hooked up to the second terminal of the two terminal sensor.

[tcom]

Both sensors are on the passenger side head. It begs the question why would it make a difference? Heat is heat and one can assume both heads given equally clean passages and fully functioning water pumps in both would be within a few degrees of each other.

The gauge functions but registers high, about a needle width and a half, maybe a little more past center. In that position coolant temp is 165*. I ran the engine at around 1500 rpm for a time parked close to a wall in my shop and the temp never got above 178* about a couple of needle widths to the left of hot. If it ever gets to the HOT line, time to stop find out what is happening.

It's not difficult to swap the sensors. I believe the leads are long enough to be able to do it.

tony

[tubman]

The reason it makes a difference is that a flathead Ford has essentially two separate cooling systems; one for each side of the engine. There are no passages within the engine where the coolant can intermix. It only does so in the radiator. Since each side of the engine is independently cooled, Ford thought it would be a good idea to keep track of them independently as well. It has turned out to be a very good idea over the years and deserves to be preserved.

You would be well served to install the temperature sensors and the related wiring according to factory specifications. The leads will be fine, since they are intended to be used that way.

[Ggmac]

Remove the single wire sender from the right head and install on the left head . Then it will be correct as Ford designed it . As tubman said , each side is independent. There is no internal mixing of water in the engine , it only gets mixed ( left and right side ) in the radiator.

[1942deluxe]

If you look at page C5 of the Early Ford V8 club 41-48 book wiring diagram it shows the two-terminal sender on the LH (drivers side head) and the single on the RH head. I have 42,46, and 48 Ford cars and they are all that way.

[tcom]

OK. Makes sense. I get it. The switch makes sure the gauge gets information from both heads simultaneously from the same locations on the heads.

I should have RTFM, but took the easy way out. I'll get them switched around. Only experience I have with Ford flatheads are a couple of 8ns and 9ns and one Jubilee I overhauled. In fact I still have a sleeve puller I made many years ago. I don't like using a welder around a block if I don't have to.

As a teenager in the fifties I drove a stock '53 Custom that didn't need serious engine work. I worked on buddies Chevies for cigarette and drive in movie money then later in life when I began collecting and restoring prewar cars I overhauled several 346 and 322 CI CAdillac motors, along with a '46 Packard and '46 Chrysler, both straight eights.

Never had my fingers deep into a Ford flathead V8. One area of my youth I missed.

I also in framed a couple of 855 Cummins engines along with out of framing a 3406 prechamber CAT motor during thirty plus years as a truck owner operator.

Probably more than anyone cares to know about me.

Thanks to all who provided the information about the switch.

tony

[tcom]

I got the sensors and wiring installed correctly. Worst part of the job was cleaning up the damned spilled coolant. The needle is now only a tad beyond the center stripe on the gauge at 168*. I borrowed my sweeties THermopen Instaread thermometer from the kitchen.

I blocked off the radiator and warmed the engine to 205*. I now have a good idea of the temperature relative to the needle positions.

Thanks again for the help.

tony

[Drbrown]

Because of inherant differences in the casting of the engine block the two sides of the engine do not run at the same exact temperature. My heads have two ports each. I now use the single stock sensor in the driver's side and a mechanical gauge sensor and heater connection on the passenger side head. During warm up they show different readings but get close together afterwards. I use 165 degree thermostates and the gauges never show above 170. Variables that can affect coolant temp and overheating is air flow through the radiator i.e. too much space between the fan blades and the radiator cores (engine compartment air just thrashes around) and whether your diving in stop n go traffic or steadily on highway.

[Tom F OHIO]

Talking about temp sensors, mine is stuck on the hot. It doesn't move. Can this be
repaired in any way? It's a 1952 dash. I figured since tcom has been working on his that maybe he or someone else can help me.

[19Fordy]

Tom, Disconnect both wires from the two terminals of the driver side sender. Then run the wire from the single terminal pass side terminal directly to the wire from your gauge.

Let your car engine warm up and see if the gauge needle moves. If your gauge needle moves, it's an indication that your two terminal sender on the driver side is faulty and needs to be replaced. As has been stated earlier, the two terminal sender is only a switch.

It has bi-metallic contacts inside that are normally closed. When the engine temp increases the points inside the 2 terminal sender normally open (at around 200 degrees) and send the signal to the gauge.

I recall that Tubman posted a thread years ago showing the innards of the single pole sender unit. Do a FORUM THREAD SEARCH for TEMPERATURE SENDER UNIT and lots of info appears.

Below are photos of the internal workings of the 2 terminal sender. Notice the adjustable contact points that open allowing gauge needle to go to HOT. The points can be adjusted with a tiny flathead screwdriver. THE ADJUSTMENT IS very sensitive.

ONE LAST THOUGHT. BEFORE DOING ANYTHING DO THIS: With the engine running and both temp. sender units properly installed you can touch one probe of an digital ohm meter to one terminal of the 2 terminal sender and the other probe to the other terminal on the two terminal sender to tell when the contact points are open or closed. With the engine COLD or just warming up the ohm meter should BEEP as the points inside the sender are closed indicating you have continuity.. When the engine gets hotter and the bi-metallic strip inside the sender heats up the points will fully OPEN (at around 200 degrees) and the ohm meter will NO LONGER BEEP indicating you no longer have continuity. At that point your gauge needle should be close to HOT.

You can also check to see if the points open by removing the sender and placing it in a pan of boiling water along with a thermometer and use your ohm meter to check for the BEEP as the temperature rises.

PS: Hope this helps. I am not an expert and sure hope others chime in.

FINAL NOTE: I have never been able to reassemble the 2 terminal sending unit so that it works when I reinstalled it. I must be doing something wrong but, can't figure it out. Any help is appreciated.

[tcom]

Thanks for posting the information.

tony

[Tom F OHIO]

Yes, most definitely thank you....