OT temp gauge on mercury

[Britcheflee]

I have put the tractor on hold for the moment until I can borrow a compression tester from a buddy to check again cylinder compression.

Going to flush and put in new coolant on the 53 Mercury.

This is the flathead v8 - the temprature gauge always is on hot and does not move much at all when the car warms up.

This appears to have two temp sensors in the block - a wire comes from the harness, goes to connector on one sensor, then from the other side a wire goes to another sensor with just a single connection and there it ends.

I am struggling to work out how this system works - would expect a circuit - how can I check this and if a sensor goes bad on one side would it then cause the other side not to work?

Thank you


Lee

 

[Jock(OR)]

To test the system, first disconnect the wire on the back of the gauge that goes to the engine. Does the gauge read the same, full hot, or full cold?

If the guage reads full hot or the same, use an ohmmeter to check that the wire to the engine isn't broken or shorted. If the wire is OK, measure the ohms from the terminal on the sensor closest to the gauge to ground (engine block). Is there a significant resistance, and is it the same for both sensors? If one is an open circuit, it is likely the culprit.

The flatheads had a water pump for each head, so it was necessary to have a sensor in each head. I believe it is designed so that the gauge will read the highest of the two sensor outputs. I think that means the least resistance to ground, but I could be wrong.

 

[JMOR]

(quoted from post at 13:25:37 08/12/12) I have put the tractor on hold for the moment until I can borrow a compression tester from a buddy to check again cylinder compression.

Going to flush and put in new coolant on the 53 Mercury.

This is the flathead v8 - the temprature gauge always is on hot and does not move much at all when the car warms up.

This appears to have two temp sensors in the block - a wire comes from the harness, goes to connector on one sensor, then from the other side a wire goes to another sensor with just a single connection and there it ends.

I am struggling to work out how this system works - would expect a circuit - how can I check this and if a sensor goes bad on one side would it then cause the other side not to work?

Thank you


Lee

lways on HOT, means that the temperature gauge never has any current going through it....just like when ign is OFF. Could be an open wiring connection. Could even be bad gauge, but most likely one of the two SERIES sensors is open. The following quick check will determine which. I say quick, because if you leave the jumper in place AND power ON (ign ON) for too long, you may burn up the gauge, SOOOO...don't leave long enough for gauge to move to end of scale.

1- Jumper single terminal sender to ground, key on, watch gauge for movement. movement= bad sender
2-Jumper 2 terminal sender, first jumper the terminal coming from single terminal sender to ground & watch gauge as before....this checks wire between the 2 senders.
2-Jumper other terminal of 2 terminal sender to ground & watch gauge as before. movement = bad 2 terminal sender
3- ground the terminal on the dash unit (the wire that comes from the 2 terminal sender___NOT the wire from ign switch) & if get reading with key on, then bad wire between dash unit & 2 terminal sender & if still no reading, check for voltage at dash unit terminal powered by ign switch & if that voltage present, the dash unit is bad.

 

[Britcheflee]

When I grounded out both sensors as you suggest the temp gauge moves promptly towards other end - so assuming both are no good - Now I need to find replacement - hopefully a fairly common part.

Lee

 

[JMOR]

(quoted from post at 18:24:05 08/12/12)

When I grounded out both sensors as you suggest the temp gauge moves promptly towards other end - so assuming both are no good - Now I need to find replacement - hopefully a fairly common part.

Lee

can't tell if you understood or not. If grounding the single terminal sensor made gauge move, the the 2 terminal sensor is probably ok. But if you had to ground the 2 terminal to make gauge move, then it is bad and the single terminal is unknown. If the latter is the case, the 2 terminal will be disconnecting the single terminal from the system, thus leaving the single as an unknown. One further step will clarify: short across the terminals of the 2 terminal device (not to ground, just terminal to terminal) & if you have gauge movement, then the single terminal device is likely OK.

 

[Jock(OR)]

Nice to see the technical information.

It looks like the 2-terminal sensor acts like an "idiot light" switch. I wondered how they worked the two sensor thing.

 

[JMOR]

(quoted from post at 22:22:18 08/12/12) Nice to see the technical information.

It looks like the 2-terminal sensor acts like an "idiot light" switch. I wondered how they worked the two sensor thing.

ock, the sensors and the receiver are both bi-metal (responding to heat), so they react slowly. The on/off switching of the sensors are averaged or 'integrated' by the receiver, such that you don't see the switching...it is all smoothed out.
Not at all unlike the Voltage Stabilizer used for instrument panel on perhaps 60's & 70's & maybe even 80's Ford cars & trucks, where "on average" they provided 5v to gauges from the 12v system (12v being up to 15v depending on state of battery & alternator/regulator). Stabilizers are on later Ford tractors too.
I see the single terminal as the always switching/averaging/integrating sensor & the 2 terminal as a 206F "upper limit HOT" sensor/switch.

 

[Anonymous-0]

New senders are available from Macs early ford parts in
Lockport new York. Dennis carpenter may also have them. I
get a lot of my flathead stuff from macs. I have also seen some
guys use two mechanical gauges mounted under the dash.

 

[Britcheflee]

Thanks for the clarification - I will check tomorrow - I need to double check on the two terminal sender but I THINK the wires are reversed - would that make any difference?

I appreciate your patience.

Thank you


Lee

 

[JMOR]

(quoted from post at 03:18:39 08/13/12)

Thanks for the clarification - I will check tomorrow - I need to double check on the two terminal sender but I THINK the wires are reversed - would that make any difference?

I appreciate your patience.

Thank you


Lee

o difference, as the 2 terminal sender is just a switch (open/closed) (on/off).

 

[Britcheflee]

No gauge movement when I short the two connectors on the top.


Lee

 

[Britcheflee]

So these are not voltage specific? I have 6 volt system - just wondering if there is a sensor out there which will do the job from another style vechicle.


Lee

 

[JMOR]

(quoted from post at 13:33:09 08/13/12)


No gauge movement when I short the two connectors on the top.


Lee

id you get gauge movement when you grounded the single terminal sensor?

 

[Britcheflee]

Yes, when i grounded the single connection sensor it moved at a steady smooth motion towards the other end (ie from hot towards cold) when I grounded the two pin sensor did the same - when I shorted the two connectors on the top of the two pin sensor it did nothing.


Lee

 

[JMOR]

(quoted from post at 17:46:03 08/13/12)

Yes, when i grounded the single connection sensor it moved at a steady smooth motion towards the other end (ie from hot towards cold) when I grounded the two pin sensor did the same - when I shorted the two connectors on the top of the two pin sensor it did nothing.


Lee

hat makes the answer very clear to me. The single connection sensor is bad. Replacement sensor for Merc or Ford V8 of correct year should fix it. The single terminal sensor is more than a switch & is therefore specific to 6v system.

 

[Britcheflee]

Thank you - I will start looking for one - I also have an interesting question for you - there is a wire which is red/green or red black - very had to tell what - it comes out of a thicker wrapped wiring which appears to go down under the car - it is hard to see but it either goes towards the kick down switch or into the gear box - what is odd is that when the ignition is on it has power but only about 3 volts or less - (this being a 6 volt system) the wire can only stretch so far and can reach the generator, the vr and not much else - any idea at all what this might be - it looks as though it was connected not so very long ago and runs through a retaining clip on the side of the oil filter. It is not for the oil pressure as that is already in place - I can send you a picture if you wish.


lee

 

[JMOR]

(quoted from post at 19:14:21 08/13/12)

Thank you - I will start looking for one - I also have an interesting question for you - there is a wire which is red/green or red black - very had to tell what - it comes out of a thicker wrapped wiring which appears to go down under the car - it is hard to see but it either goes towards the kick down switch or into the gear box - what is odd is that when the ignition is on it has power but only about 3 volts or less - (this being a 6 volt system) the wire can only stretch so far and can reach the generator, the vr and not much else - any idea at all what this might be - it looks as though it was connected not so very long ago and runs through a retaining clip on the side of the oil filter. It is not for the oil pressure as that is already in place - I can send you a picture if you wish.


lee

ure, send picture. Long shot, not being there, but I would look for places within wire's reach that have a terminal & no connected wire. What does end of wire have? Connector, plug, socket?, ?

 

[36 Coupe]

The single terminal sender has a heating coil in it and is 6 volt.These senders are 55.00 each in a new catalog.

 

[36 Coupe]

Lets back up and test the senders with an ohmmeter.Ignition switch OFF.The 2 terminal sender should read zero ohms cold.The single terminal sender should read low ohms.If it reads open the heater coil is open.You should see 10 ohms.

 

[36 Coupe]

Early V8s had just one sender in the left head.The system dosent work the way you think,the single terminal sender reads the temperature.The two terminal sender opens on overheat.The gauge rests on hot even if you disconnect the sending wire.

 

[Britcheflee]

With the ohmeter I put one side to the connector on the top and the other to ground on the single connection and across the two connectors on the two connector sender or from one side to ground?

Thankyou



Lee

 

[JMOR]

(quoted from post at 10:40:08 08/14/12)
With the ohmeter I put one side to the connector on the top and the other to ground on the single connection and across the two connectors on the two connector sender or from one side to ground?

Thankyou



Lee

ust go purchase the single terminal sensor & move on back to the N. 36 was responding to someone else in his, "it doesn't work like you think", not you, Lee. You & I KNOW how it works!

 

[36 Coupe]

On the 2 terminal sender you measure across the 2 terminals.This is a simple series circuit.

 

[36 Coupe]

Ring terminal fastened with a screw ,no modern junk connectors.

 

[36 Coupe]

Leave the 2 pin sender alone.I was working in a Ford garage when the system was in use.I had to troubleshoot it.Listen to an old mechanic who was there.If you replace the single pin sender do NOT use teflon tape or any sealer.

 

[36 Coupe]

Stop assuming,you are wrong.