Water Temperature Sensor

[Lazerwolf]

Looking for general opinion on this. My factory water temp gauge is not working so I bought one from Auto Meter. In the installation instructions, they mention that if you don't have easy access to a water passage, to install this in your heater hose. They also sell a kit for this. This got me thinking that if installed in the heater hose, it would not be as accurate. It just seems to me that up and away from the engine where there is some air flow, it would read lower than it should. Also, would this be even less accurate if the heat in the cabin is off? Am I off base on this?

 

[HEMI-ITIS]

BBM waterpump has 4 different holes to use,,,,,,,,,,,,,,,

 

[bigmanjbmopar]

Yeah, what motor? how do you know your gauge is bad and not just the sensor?

 

[Lazerwolf]

Details would help. Car is 74 Charger SE with original 400 engine, water pump and housing. Also has AC and PS so water outlet on housing is on passenger side of car. Still researching how to check gauge but it did not move when I ran wire directly from battery to temp sensor wire.

 

[kiwigtx]

Details would help. Car is 74 Charger SE with original 400 engine, water pump and housing. Also has AC and PS so water outlet on housing is on passenger side of car. Still researching how to check gauge but it did not move when I ran wire directly from battery to temp sensor wire.

Did the gauge needle violently vibrate before emitting smoke when you did that??

The best way to test the gauge operation is to short the temperature sensor wire end to the block / ground. This should peg the gauge at full arc. After that test is passed, you can pretty much assume the sensor head itself is faulty.

 

[bigmanjbmopar]

lol fried the limiter well do you have a ohm meter to test the sensor with? I would suggest get one and a temp gun use the meter on ohms settings to read the sensor change as the motor warms up and use the temp gun to watch the temps as they go up. Putting 12 vdc on the wire was not a good idea, hopefully you did not do any damage to the circuit board on the gauge cluster.

Can you do like Kiwi says and with the key ON NOT running (motor already warmed up) take the temp sensor wire off the sensor and either use a piece of wire or a paper clip to ground it to the block or frame etc make a good ground connection, then go look at the gauge and see if it went all the way full? if it did the gauge is working, if it only went 1/2 then the gauge is bad (can be fixed) if it did nothing, that either the wire to the sensor is bad or there are issues with the circuit board on the cluster.


Here are the wiring diagrams for your car. Looks like a violet wire from the clusters circuit board to the temp sensor on the motor.

http://www.mymopar.com/downloads/1974/74CoronetChargerA.JPG

http://www.mymopar.com/downloads/1974/74CoronetChargerB.JPG

 

[Lazerwolf]

Somewhere on here, I found a thread saying to jump the sensor wire, which is violet, to the ground (black) on the battery. Turn the ignition to "on" and the needle should start to move. This is the procedure I followed and my needle didn't even twitch. However, I do suspect that it could be in the wiring between the firewall connector and the sensor. When I bought the car, the sensor connector was just hanging besides the sensor, not connected, and they had done a poor job replacing a section of wiring prior to the sensor connector. Not sure if it matters, but the sensor wire looks like maybe a 18 gauge and they replaced a foot or so of it with a 14-16 gauge wire. There's no markings on it to verify and I have yet to change it.

 

[bigmanjbmopar]

How hard is it to get you cluster out? Sounds like you need to replace the wire to the fire wall at least ace hardware has wire by the foot you can get. When you said 12v we thought you meant the positive side lol grounding can be done at the block or frame if the negative of the battery is connected to the block like normal. You can use an ohm meter to check the wire end to end. You can do the same check from the inside to cluster, find the violet wire from the dash to the fire wall connector and ground it and check the the gauge.