Temo gauge goes to full after car runs for about 5 minutes.

[Dominic Torreto]

So I have a 1970 dodge charger 440. Recently the coolant temp gauge went to full after 5 mins. 1. Engines not running that hot used a laser temp gun plus its 5 mins. 2. I did the old ground check to check for broken wire/guage and it checked out went to full when you grounded it and it went to 0 when you unplugged coolant sensor connector like it should. 3. Bought a brand new coolant sensor/switch sending unit and that wasnt the problem. 4. Radiator gets hot like it should so I know its not the thermostat being shut closed. 5. Checked for air pockets and I burped the system added and topped off radiator even did it after it ran. Guys out of ideas anybody have this problem? I searched this forumns/google and youtube looks like I am the only character in the world with this problem. Prove me wrong here guys.

 

[INTMD8]

What is infrared temp at sensor location at the point your temp gauge reads "full"?

Is the temp sensor connected to the fuel level gauge?

I ask because temperature isn't full or empty so what actual numbers are you seeing?

 

[Mopar Hunter]

It’s got to be in your gauges, if the infrared temperature gun reads ok.

 

[kiwigtx]

1. Engines not running that hot used a laser temp gun plus its 5 mins.

Do not rely solely on a laser temperature gun - they are notoriously inaccurate.

Unless you have verified the readings against another known source, I wouldn't base any rash decisions upon the readings from the gun.

Good Multimeters have a temperature function, and usually come supplied with a set of probes - if you can access one from a friend you can compare results.

 

[kiwigtx]

Do not rely solely on a laser temperature gun - they are notoriously inaccurate.

Unless you have verified the readings against another known source, I wouldn't base any rash decisions upon the readings from the gun.

Good Multimeters have a temperature function, and usually come supplied with a set of probes - if you can access one from a friend you can compare results.

Also you will get fluctuating readings from shiny surfaces compared to dull finishes.

 

[twecomm]

Based on what you describe, strange that this all of a sudden started happening. Something I have done on my 383 to prove the gauge is reading properly is :
Drain enough out of the rad so the fluid level is below that of the temp sensor so you won't have a mess to clean up. Remove the sender from block and temporarily use some clip leads to re-connect the loose sender wire and a good ground connection to outer threaded body of the sensor. Boil some water in a pan or better yet, a Pyrex measuring cup. If a pan, put the pan on a folded towel or something to electrically insulate it from cars chassis. Use a kitchen-meat thermometer and dip both the sender and thermometer in the water. Turn on the ignition so gauges work without starting the engine. Observe the thermometer temp vs. your gauges reading. You can also use your IR gun to measure the waters temp to see if it agrees with the kitchen thermometer.
You can also do a similar test of senders resistance with an ohm meter. With sensor at ambient temperature (cold resistance) this number should meet the spec to be proper for your gauge and engine. Record the resistance from the boiling point through cool down off the water.
Also, using an ohm meter, measure for resistance between senders body and engine block or battery minus terminal. The sender must have a good ground for gauge to read properly. I've read accounts of too much teflon tape on threads that can make a difference.. Also it's possible that your gauge volt regulator may be defective, but that's unlikely if fuel and oil press gauges are working properly. May be as simple as a bad temp sender..

 

[Cranky]

I'm thinking bad temp sensor or like mentioned above, too much teflon tape if you used that on it....

 

[AR67GTX]

Mine would do that when the instrument voltage regulator was going bad. It would start after the car had been running several minutes and then the temp gage and fuel gage would start going full scale. After parking and cool off it would reset and repeat the next time I drove it. However, if your fuel gage works and it’s not acting in similar fashion it’s probably an issue other than the IVR.

 

[pnora]

If it was the IVR all 3 gauges would be acting the same way. Excess tape on the threads would isolate the sender from being grounded and if anything the gauge would read low or not at all. Its either a defective sender or the wire is grounding somewhere. What part number sender are you using?

 

[Dominic Torreto]

So I have a 1970 dodge charger 440. Recently the coolant temp gauge went to full after 5 mins. 1. Engines not running that hot used a laser temp gun plus its 5 mins. 2. I did the old ground check to check for broken wire/guage and it checked out went to full when you grounded it and it went to 0 when you unplugged coolant sensor connector like it should. 3. Bought a brand new coolant sensor/switch sending unit and that wasnt the problem. 4. Radiator gets hot like it should so I know its not the thermostat being shut closed. 5. Checked for air pockets and I burped the system added and topped off radiator even did it after it ran. Guys out of ideas anybody have this problem? I searched this forumns/google and youtube looks like I am the only character in the world with this problem. Prove me wrong here guys.

So I honestly was surprised with all the ideas. To awnser the most common idea that was brought up no I did not use teflon tape. As for the sending unit goes its doing exactly what the old one did. I am going to try some of your ideas on here and keep you guys posted.

 

[Dominic Torreto]

BTW the temp guage worked since 2012. It just started doing this and how important is this job? Its the last job before I do the final test drive if that passes then car gets plated. Litterly the last job.

 

[Cranky]

Do not rely solely on a laser temperature gun - they are notoriously inaccurate.

Unless you have verified the readings against another known source, I wouldn't base any rash decisions upon the readings from the gun.

Good Multimeters have a temperature function, and usually come supplied with a set of probes - if you can access one from a friend you can compare results.

The high end guns are supposed to be pretty good even at lower temps....

 

[Dominic Torreto]

What is infrared temp at sensor location at the point your temp gauge reads "full"?

Is the temp sensor connected to the fuel level gauge?

I ask because temperature isn't full or empty so what actual numbers are you seeing?

Just did your test right around 100 degrees Farenheight.

 

[Dominic Torreto]

If it was the IVR all 3 gauges would be acting the same way. Excess tape on the threads would isolate the sender from being grounded and if anything the gauge would read low or not at all. Its either a defective sender or the wire is grounding somewhere. What part number sender are you using?

My problem is this. When you unhook the Temperature sender it goes to 0.

 

[pnora]

My problem is this. When you unhook the Temperature sender it goes to 0.

Which it should. What part number sender are you using?

 

[Dominic Torreto]

Which it should. What part number sender are you using?

Ultra power 1T1010

 

[dadsbee]

I've found that a good temp sender has an ohm reading of around 320 to 360 ohms at 70 degrees... as it uses the same ohm range as a fuel sender for the gauge profile of 70 ohms to 10 ohms. Want to check it. Boil some water, put the sender in it and see if it reads about mid gauge scale which would be around 40 ohms.

 

[pnora]

Ultra power 1T1010

Hah. Junk. Cheap 1.76 rock auto junk. I had that same unit just do the opposite. Kept showing to cold. Get this Standard one TS17.

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[Dominic Torreto]

Hah. Junk. Cheap 1.76 rock auto junk. I had that same unit just do the opposite. Kept showing to cold. Get this Standard one TS17.

​

I want you to be as descriptive as you can on your story but first I want you to realise that the sending unit on there did the exact same thing as the Rockauto one. The Exact sane thing. Please tell me your story of what happened as detailed as you can.

 

[pnora]

I want you to be as descriptive as you can on your story but first I want you to realise that the sending unit on there did the exact same thing as the Rockauto one. The Exact sane thing. Please tell me your story of what happened as detailed as you can.

Installed it and it seemed ok. Next time I drove it the temp was reading very very low and I was in the 180-190 range. I bought the Standard TS17 and it has worked perfect. I have the old Miller special tool gauge tester which is no more than 3 sets of specific range resistors. Gauge would read low, half, and high. Point is Cheap is no good.