Temp sending sensor Question?????

[vanrj1]

I put a Mopar brand temp sensor in my car today (NOS like from 1989) and I don't get any reading at all. When I run a ground to the wire it buries the gauge so would that not mean the connection is good to the gauge?? Why would I get zero movement at gauge when connected to sensor. I have an infrared thermometer, (very accurate) and I get about 184° to 190° on the engine (heads, intake and water pump).

 

[bm02tj]

check with your ohm meter between the stud and the body of the sender also from the body of the sender to the engine as the threads need to ground through the thread sealant

 

[vanrj1]

check with your ohm meter between the stud and the body of the sender also from the body of the sender to the engine as the threads need to ground through the thread sealant

Ok, I used an adapter also so maybe there is no ground. If that is the case, is there any tricks to help get a good ground??

 

[bm02tj]

some times just tightening it more will get you metal to metal in one spot but check with your ohm meter before you tighten

 

[vanrj1]

some times just tightening it more will get you metal to metal in one spot but check with your ohm meter before you tighten

Ok, I don't know much about the meter but when I touch the 2 leads together it goes to zero as it should, when I touch the pos lead to the sensor connector and ground to engine block, the dial goes about 1/4 of the way over. this was with engine running and thermostat open. Also tried other ground points on the engine and all are the same reading. It will not move my gauge in the car though. I then loosened and tightened a few times to see if I could get a better connection and no change.

 

[krowbar]

If you are using an adapter the sending unit might not be in the coolant flow depending on where your sending unit is located. Air pocket? You might have a junk sending unit? I just put a NOS voltage regulator on my car and I think it's junk too.

 

[super-bee_ski]

In my opinion,
As soon as you "grounded" the sensor and it deflected...
I would say the sensor works...


As you state...:
-Ok, I don't know much about the meter but when I touch the 2 leads together it goes to zero as it should, when I touch the pos lead to the sensor connector and ground to engine block, the dial goes about 1/4 of the way over. this was with engine running and thermostat open. Also tried other ground points on the engine and all are the same reading. It will not move my gauge in the car though. I then loosened and tightened a few times to see if I could get a better connection and no change.

Essentially you are performing a "continuity" check.
When the multi-meter leads are touching...(in the Ohms setting)...you are showing a "SHORT"
That means: "No resistance" or no Ohms. (complete continuity from black lead to red lead & thru meter)

When you have resistance: Such as "meter dial goes about 1/4 of the way over"
If your meter does not "deflect" then it is an "OPEN" and that is the opposite of a "SHORT"
You are reading a resistance. sensors need resistance.
The ultimate resistance reading is an "OPEN". No continuity at all.

Check voltage at sensor with engine warm. It should read: 0.8 VDC to 1.5 VDC.

NOTE: do you have a 2 "terminal" sensor or a 3 "terminal" sensor?

I would say your sensor operates.

BIG QUESTION: Why did you change your temp sensor?
Same reason? No reading?
Then that means 2 sensors installed and no reading.
Time to check wiring.

 

[vanrj1]

In my opinion,
As soon as you "grounded" the sensor and it deflected...
I would say the sensor works...


As you state...:
-Ok, I don't know much about the meter but when I touch the 2 leads together it goes to zero as it should, when I touch the pos lead to the sensor connector and ground to engine block, the dial goes about 1/4 of the way over. this was with engine running and thermostat open. Also tried other ground points on the engine and all are the same reading. It will not move my gauge in the car though. I then loosened and tightened a few times to see if I could get a better connection and no change.

Essentially you are performing a "continuity" check.
When the multi-meter leads are touching...(in the Ohms setting)...you are showing a "SHORT"
That means: "No resistance" or no Ohms. (complete continuity from black lead to red lead & thru meter)

When you have resistance: Such as "meter dial goes about 1/4 of the way over"
If your meter does not "deflect" then it is an "OPEN" and that is the opposite of a "SHORT"
You are reading a resistance. sensors need resistance.
The ultimate resistance reading is an "OPEN". No continuity at all.

Check voltage at sensor with engine warm. It should read: 0.8 VDC to 1.5 VDC.

I will try this later tonight

NOTE: do you have a 2 "terminal" sensor or a 3 "terminal" sensor?

I would say your sensor operates.

BIG QUESTION: Why did you change your temp sensor?
Same reason? No reading?
Then that means 2 sensors installed and no reading.
Time to check wiring.

Ok, I have a single sensor I guess. It is a fresh engine and new wire harness, just now installing the sensor for stock gauge. here is a pic


- - - Updated - - -

If you are using an adapter the sending unit might not be in the coolant flow depending on where your sending unit is located. Air pocket? You might have a junk sending unit? I just put a NOS voltage regulator on my car and I think it's junk too.

The sensor does not protrude out as much from the adapter as it would with out it so that might be an issue as well???
View attachment 127791

 

[bm02tj]

check with your ohm meter from the hex on the sender to block and it should be the same as when you put the leads together to prove you have a good ground for the sender to work

 

[vanrj1]

check with your ohm meter from the hex on the sender to block and it should be the same as when you put the leads together to prove you have a good ground for the sender to work

Ok, I will try that!

 

[doug428]

Ok, I will try that!

I have same problem
my gauge didnt work when I bought the car
new harness and new sending unit
the temp gauge will actually go up a little 120 max when I know its really at 190 from second gauge I have.

same problem with oil pressure gauge

when I ground either gauge out they both move all the way up.
I have 5 volts at each wire to sending unit.

I have updated circuit board in dash with built in 5 volt limiter.
curious what you come up with.
good luck.

 

[Dako]

vanrj1,

On my single 4bbl manifold (Polys are great!), I had to do the same thing...use a threaded sleeve, as the hole was too big. I cut the sleeve in half to expose more of the sensor. Don't know that this will help you as for the gauge not reading, just letting you know I also had concerns about exposing the sensor enough to get a good reading.

Do you have your original sensor? I would try swapping it in and see if you get a good reading.

 

[vanrj1]

vanrj1,

On my single 4bbl manifold (Polys are great!), I had to do the same thing...use a threaded sleeve, as the hole was too big. I cut the sleeve in half to expose more of the sensor. Don't know that this will help you as for the gauge not reading, just letting you know I also had concerns about exposing the sensor enough to get a good reading.

Do you have your original sensor? I would try swapping it in and see if you get a good reading.

I didn't think about cutting it down. I need to check ground and if I get that good connection I may cut my adapter sleeve down a little. I have the original 2bbl intake I will look and see if the sensor is still in it. Thanks..

 

[vanrj1]

Ok, this is what I get when touching sensor shaft and ground on the block. would it be 2 ohms? It is making a ground but is it good enough?

 

[krowbar]

Essentially you want 0 ohms but you are grounding to the block and you have to go through the intake and heads which will draw a little continuity. Should be fine to check the sending unit. Get some boiling water and test the unit in that. You will know then if it's the sending unit itself at fault.

 

[ChargerRTguy]

I have a similar problem, my gauge reads to about 120 when running, but when I shut it off and then turn the ignition back on, it reads 180. I'm thinking it might be the sensor, I have a NOS one, that I plan on using. See what happens. The rest of the gauges seem to work.

 

[Moparsmitty]

Krowbar is correct. You want 0 ohms of resistance from the outside housing of the sensor, but measure to the negative post on the battery to measure the whole grounding circuit. Any resistance in the entire temp gauge circuit will cause false readings.

 

[bm02tj]

you have over 200 ohms so no you will not show temp

I called Bluestreak and asked for specs

220F is 24.7 Ohms
100F is 152.2 Ohms

so less sealant so it will ground out and work please note brass fittings are almost self sealing so only a little sealant

Bruce

 

[krowbar]

Looks like he has it on the x10 setting. So that would be about 22 ohms right?

 

[bm02tj]

Yes you are right I have to stop looking at this when I run by while eating lunch and pay more attention
Thanks