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  #1  
Old 06-11-2008, 11:15 PM
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Anyone shot their motor?

With a Infrared Thermometer I mean...

Been thinking about doing this to verify my temp gauge but not sure if it is going to give me the reading I want. I have access to one but don't know what allowances to make with it or where to take readings.

I got a new Radiator going in and want to then verify the "real" engine and coolant temperatures of before and after to see if my gauge is close to right. Or recalibrate that thing in my mind if not. Plus it will help me with the before and after there to know if its really what it is showing.

The gauge does occasionally jerk up and down about 10 degrees like it has a bad voltage input but normally (99 percent of the time) it will run steady. So I want to verify if that jerk up is errant as I think it is. It normally runs about 97 C but sometimes it will hit 100C. But when it jerks up for a few minutes those few times it will jerk to 105-110C then drop back in a minute or so in two jerky movements to 97 or so.

It's been in the high 90F to 100F around here for a couple weeks but it also ran 95-97C degrees in cool weather a few months back too. It seems to run 97 to, at most, 100C no matter what. Even with AC running full blast in 100F weather. I have no idea if its even right though. So I would like to verify with a good Infrared thermometer if I can.

Any input on running these diagnostics using an infrared thermometer welcome.

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  #2  
Old 06-12-2008, 12:42 AM
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yes, I've got an IR thermometer, its great, I can check the radiator for clogged passages, (cold spots)

I verified the temp gauge on my boat and various benzos (all within a few degrees ) Checked the intake mainfold temps after I modded the intake.

and my dogs coat can hit 116 degrees in the summer sun before he decides its time to go lay under the porch. (black lab)
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  #3  
Old 06-12-2008, 12:46 AM
Craig
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Is the temperature gauge jumping by itself, or is the fuel gauge also jumping? If they are both jumping together it may be a ground issue. I solved that problem by adding a separate ground wire from the instrument cluster.
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Old 06-12-2008, 12:48 AM
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Just the temp gauge.
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  #5  
Old 06-12-2008, 12:52 AM
Craig
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i don't know, it could be the gauge, a connection, or a wire.
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Old 06-12-2008, 12:56 AM
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Its probably the temp sendor.
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  #7  
Old 06-12-2008, 01:15 AM
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Quote:
Originally Posted by 79Mercy View Post
Its probably the temp sendor.
I agree, it is composed of a sliding variable resistor inside. They are going to wear and even get oxidation inside eventually. So simple to change out try another one.
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Old 06-12-2008, 01:40 AM
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Originally Posted by barry123400 View Post
I agree, it is composed of a sliding variable resistor inside. They are going to wear and even get oxidation inside eventually. So simple to change out try another one.
The one in the head, not the dash.
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Old 06-12-2008, 06:46 AM
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Quote:
Originally Posted by Mister Byrnzoil View Post
and my dogs coat can hit 116 degrees in the summer sun before he decides its time to go lay under the porch. (black lab)
I'm glad I'm not the only one who thought of shooting the dog with the thermometer... He's annoyed by the beep it makes now and walks away any time I get it out.
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  #10  
Old 06-12-2008, 07:45 AM
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My wife has the same response
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  #11  
Old 06-12-2008, 10:13 AM
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Oh goody... more ideas to use the thermometer on. Wonder how the Cat is going to like this? And I also have the probe so I wonder where I could stick that!

Does the Gauge receive more voltage to increase its reading? Or the other way around?

i.e. Low reading is more voltage and less reading is less voltage?

Or the other way around would be the gauge initially receives very little voltage but then as the temperature climbs it receives increasing voltage.
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  #12  
Old 06-12-2008, 10:45 AM
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The Temperature-sensor in the block isnt a mechanical device as described above!

Its a Thermistor. A Thermistor is a specialised resistor that changes resistance due to temperature. It has NO Moving parts....

The guage is supplied by a regulated voltage. The other side of the guage is grounded via the Thermistor.
As the temp increases, the resistance of the thermistor falls, increasing the current flow, and guage reading....
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  #13  
Old 06-12-2008, 10:54 AM
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Ok then it sounds like its more likely the Sender then in this case. If it was Falling in temp reading it could be ground or lose wire.

But in this case its increasing in temp reading so, periodically and momentarily, the sender is sending a small voltage spike resulting in a higher reading.
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  #14  
Old 06-13-2008, 09:38 PM
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I bring this back up for a report.

I shot the thing numerous times today with the brand new Infrared and the highest reading I can get coming off the hose right out of the block is 84C and thats with the Pod Temperature reading of 98C and outside temperature was 90F... and after the good heated run from work to home. So its the sender is reading wrong or something like that.

Any of you that are getting high readings need to think about this. It might not be right.

I am going to go ahead and put this new Radiator in anyway. Because of the cracking nipple issue, even though the fix has lasted a week in hot weather I don't trust it. But its not running hot. So I am going to try and replace that Sensor as well. If that doesn't fix it, I will recalibrate my brain and see if its, at least, linear.

And another good thing is that I finally installed my Alpine 9664 radio in the thing today and it is superb. I put the included iPod cable into the Glove box. The iPod play is stupid good. CD Play excellent and Radio good too. Now on to fixing the Power Antenna!

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1983 300D-Turbo - Deep Blue w Palomino MB Tex (total loss in fire 1/5/09 RIP)
1995 E320 W124 Polar White/Grey Mushroom MB Tex
2005 F150 Supercrew - Arizona Beige - Lear topper
1985 Piaggio Vespa T5 - Black and Chrome

www.cphilip.com
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