Water temperature gauge not functioning - 1970 Charger 440

[matchek]

Hi my water temperature gauge does not seem to function.  Not sure how long it take to see it warm up but let it run for 15 minutes and still cold.   What would you go about doing to repair this?     I attached a pic of what my temp sensor looks like.   I think the engine is a 1972 model.    This is very important - cannot drive like this.

Matt

[matchek]

pic of engine focused on temp sensor

[70 sublime]

Looks like there is a join in the wire close to the end
Are you sure the wire is good ?

Not sure if you take the wire off the sensor and ground the end to the engine block if that should make the gauge move if all the wiring and gauge are good ?

[matchek]

Thank you great idea!   And yes, did that and the temp gauge went up and then took it off the block and went down.  So I guess it is just a the $10 sensor?    

I don't know much about the car as just got today!   Dumb question, but how do I check the water level?  Do I add water to the white container until it fills up or fill the main radiator until it fills up?    The reason why I ask is I want to rule out that the water level is low.

[Mopar Nut]

Fill the main radiator with 50/50 antifreeze mixture about a inch to inch 1/2 from the top. Don't over fill.



The white container that you talk about is for the windshield washer fluid.

[matchek]

Thank you Mopar nut!   I am glad I double checked.   When I had my 90 Mercedes, that white container was for coolant.   Appreciate it.   I have an owners manual and repair manual ordered  but they won't come until Monday and Thursday so just excited to get started with figuring this out.  

So when you open the radiator cap, you do want to be able to see some liquid but just not at the top, correct?    I opened it and did not see any.

[70 sublime]

Thank you Mopar nut!   I am glad I double checked.   When I had my 90 Mercedes, that white container was for coolant.   Appreciate it.   I have an owners manual and repair manual but they won't come until Monday and Thursday so just excited to get started with figuring this out. 

So when you open the radiator cap, you do want to be able to see some liquid but just not at the top, correct?    I opened it and did not see any.

Yes you will want to see some coolant 
Should fill it so the rad tubes are covered and about half way to the filler neck
Needs to be some space or it will just boil over till it finds it happy level space 

[matchek]

As an update,  added coolant to the desired level and replaced the like-for-like temperature sensor and it still does not work. 

For clarification when I ground the wire to anything other than the metal threads of the temperature sensor that connects to the engine block, the temperature gauge goes all the way to right (note engine was warm too). 

When I plug in the temperature wire and connect the sensor thread, the gauge goes to 0. Same thing if I ground the temperature wire to the sensor thread - goes to 0.    Something ain't right - this is so frustrating as I cannot drive it like this.

[matchek]

By the way for the 2nd generation folks, does your temp gauge go to 190F as soon as the car warms up? How long does it take to move and get to the set point?  Want to rule that out as the repair manual says it takes a long time to warm.  But when the engine was blowing hot air, the temp gauge was still 0. 

Also when you turn your key before starting your car, what gauges go all the way to the right please?    For me the fuel and battery have readings, but my temperature gauge stays 0. 

[Nacho-RT74]

no one gauge must get all the way out to right.

battery ( ammeter I guess you meant ) must be at the center as much as posible.

The temp gauge usually moves allmost at the time the engine begins to warm up. The scale goes from 100° to 250° F. You can check the gauge reading speed with your fuel gauge. It takes around couple of seconds to get you on reading. Since the warm up process is way slowler, the gauge reading will be allmost at the same time

[70 sublime]

I have driven my 69 that has a 71 383 motor in it for the last 3 years with no temp gauge and have gotten along just fine
My 71 motor has the sensor with the 2 wires for the warning light set up and have never gotten around to change it

Not the end of the world

[matchek]

Thank you guys - yeah it is not but very frustrating it is so nice to have.

By the way, just to rule this out that I have to have the sending unit threaded a certain depth, how far is is your temperature sending unit to the block?   Just snug or forced to where you no longer see threads?  My sending unit is snug with about 3/16" of threads showing. 

[Nacho-RT74]

all threated in up to the shoulder, without anykind of sealer. It needs to be threated in metal with metal since it takes ground via the threads. Maybe just the last portion of the threads could get some sealant

[matchek]

I attached a new temperature sender I just bought from Amazon and the temp gauge still does not work. Is this the right one?   Is there a brand that is better than others?  I tightened it where up to about 1/2 of the group of threads on the right are still showing.  At that point it was tight and not leaking.  I guess I could force it and keep on going to try to hide all of the right-side threads but not sure if I have too.   For clarification are we supposed to tighten this as to all of the larger threads are inside the block?  This is very important as I don't think the temperature sending unit is closing a circuit.

As an update I bought a test light and a voltmeter.  I am getting pulses with a a test light and getting random pulses of around 3 volts from the temperature sender wire.  When I ground the sending wire, the temp gauge goes to 250F like it should.     

I cut the temp sending wire pig tail off because I thought maybe there was a problem with the pig tail.  With a bare sending wire, I connected the voltmeter to the wire and to the sending unit and don't get much voltage.  The old sender has resistance of around 285 ohms cold and around 120 ohms coming out of boiling water.   

[Nacho-RT74]

The ohms rate should be between 10 ( +/- 2 ) ohms for max and 70 ( +/- 5 )  ohms for min. It applies for all senders since all gauges are calibrated the same and works with the common  VL. The only diff between gauges is actually the face

[matchek]

Thank you Nacho - makes sense.    I want to rule out that the gauge (especially) is not the problem - I don't think it is, but don't know for sure.  I went ahead and bought a resistor assortment kit from Amazon  and plan on attaching a resistors or around 10 ohm, 45 ohm, and 75 ohm and connect to the sending unit and ground and see if I can get regular temp gauge readings.  This is the only way to verify that the wiring and gauge are working properly and the only issues is the coolant sensor.   I wish there was a Radio Shack around because I won't get the resistor pack until Monday from Amazon.

The old coolant sensor had resistance of around 120 ohm (hot) and 290 ohm (cold) so that would make sense that no current is going through this circuit.  Looks like I need the resistance to to at least 80 ohms to start seeing something on the gauge.   I did not test the new sensor but it looks the same - a "Model TS17" from Standard Motor Products.

[Nacho-RT74]

Check the sticked thread about cluster restoration on this same board section and there you find how to build a gauge calibration tool/tester with the propper resistors values

[matchek]

Thank you Nacho - yeah I saw that -  I don't know if I need that if just add resistors to a circuit.  That looks time consuming.   

By the way, if I hold put the sensor in boiling water and pull it out, it should have a resistance of around 10 ohms, and when it cools it should go back up to around 80 ohms, right?  When I put my voltmeters I get reading much higher than that. 

[matchek]

Well FANTASTIC news - it is fixed - temperature gauge now works, knock on wood!      The short of it is that it was faulty temperature sensor.  The existing one and the new one from Amazon were bad.   I wound up getting one that worked from NAPA later today. 

How did I arrive at trying out another sensor?   First, I verified that I was getting current to the gauge by grounding it.  Then I put a light tester at the sending unit and verified pulsing. Put a voltmeter and it was around 3V, but was hard to read because so much reading movement. Then measured the resistance of the OLD sensor (room temp and after boiling in water) and noticed that the resistance was high in the sensor even after boiling in water (~ 300 ohm cold and 190 ohm hot) - I could tell that the gauge would not work with this sensor.    I broke out the repair manual and re-sketched the wiring diagram on paper to think about what it could be.  It got me thinking it has to either be the sensor (likely), a faulty gauge that operates only at very low resistance (unlikely), frayed wire somewhere (unlikely).  On a whim,  I measured the resistance of the Amazon sensor and lo and behold, it had very HIGH resistance, like 2,500 ohm at room temperature.    This is probably either a bad sensor or for for a newer car.   I saw that some cars like new Hondas have sensors that high.

So on another whim, I went to NAPA and asked if they had a sensor for a 70 Charger in stock - and they did.  I put a tester on it and it read something like 150 ohms at room temperature.  I got excited because I knew that 70F it had a resistance of 150 ohms at room temperature, there was a good change that 190F water would reduce the resistance to a level to work the gauge.   Installed the new sensor and sending unit connector.  Added coolant to the desired level.  Started the car and within 10 minutes 185F running on the  gauge!  Whew ew!   So excited. Thank you all for your help!  I thought I would save money from Amazon but sometimes you get what you pay for.  Now it is fixed and have a new multimeter and other tools for "free". 

So looking forward to the peace of mind of driving with working gauges (knock on wood).

[BMOTOXSTAR]

I am having the same issue on my '73 400. Went to Napa, got a new sensor. Same, no reading. Or I should say random, worked for 3 minutes after install then stopped working.

New hoses, thermostat, water pump, thermostat even a new end on the wire that goes to the sensor...

[Nacho-RT74]

Allways the temp gauge barelly responds or respond erratically, will be the sender. There is no way mechanic parts such as water pump, t-stat or whichever else, will make that kind of weird erratic readings.

[DownZero]

Not always true. Did you ever see what happens when you have a water pump cavitate?

[Nacho-RT74]

I have read but never see personally that problem.

[BMOTOXSTAR]

Thanks Nacho man !!!  Yeah I am going to follow the wire to the bulkhead just incase, then buy another new sender.