self destructing pyrometer

[Gizmo 007]

Traveling back from my home to college today, my autometer ultralite pyro decided to go berzerk! At first, it would flutter for a second or so, then it went completely nuts and started bouncing from 0 - 1600 really quickly . Now, it won't move at all. It stuck on 400* and won't go up or down. I checked all my wiring, but it all checks out. Anyone have this problem? If so, was it the probe or the guage? The guage / probe is about 1. 5 years old.



I tried using the search feature, to no avail.



Thanks.

 

[willyslover]

replace your probe. . it just went to ground or burnt the end off. . had the same thing on another brand. . get a replacement thermocouple

 

[ToolManTimTaylor]

Yep I would pull that probe before it goes into the really really fast blender I saw a k themo snap off and go into a little bitty 2. 2 turbo once Eeeessch yuk.

 

[rfcom]

Decision made

I've been debating (with myself ) about where to put the pyro probe. Thanks for the post Gizmo, now I know I'm putting it after the turbo. My bombs will be very mild anyway.



Jim

 

[willyslover]

rfcom. . just remember aft reads low by 300* or more... and you'll be ok

 

[Gizmo 007]

thanks guys! I was hoping it would be the probe and not the gauge, but I wasn't sure. I'll try to get a new probe this week.



My probe is mounted between my compound turbos at the moment, all this talk of snapping off a probe is gettin' me kinda skeered. But I'm not gonna lose sleep over it. I've had worse.



Again, THANKS!

 

[K_Arts]

Which model of gauge do you have?



I had 4 different Autometer EGT gauges that did this same thing. I went through all kinds of test with autometer. Come to find out they make 2 different types of gauges. One is where the Probe connects directly into the back of the gauge (this is the new gauge) and the other is where the probe connects in to a little 2 inch by 2 inch black power module (this is the old gauge), in which is where you connect your power and ground.



Autometer told me that they have had numerous amounts of these black power boxes fail. I then sent them my gauge and the black power module and they then sent me the new gauge in return.



I would honestly check out this box (if you have one) before you buy a new probe. If you don't have this box, check out your power and ground cables. I highly doubt that the problem is your probe... . sorry guys.



Kev

 

[Gizmo 007]

K_Arts, I've got the one where the probe connects directly to the guage. No little black box. It's the ultralite series 0-1600*.



I checked the power and ground, all ok. Really don't know how to check the probe, bu I have continuity from the back of the guage to the leads on the probe. I'm stumped.

 

[K_Arts]

The first test that Autometer had me do was when my gauge started going haywire, they said step on the gas pedal. If your needle stops bouncing around and starts registering temps, It definately is an electrical problem.



If I suspected it was the probe, they told me to take the gauge and probe out of my truck, hook them up to a standard 12v battery (fused off at 1 amp), then boil some water on the stove. does the Probe register temps, if so, it's not a probe problem. If it does not register anything, then it could be a probe issue.



Also, with the gauge setup outside of the vehicle, it is easier to change out the power and ground wires to see if it is an electrical problem or not. As I stated above, I had this same problem with 4 different gauges, all led back to electrical problems. Which is why I would thoroughly check this out before buying another $50 + probe if it possibly is not the problem. The last thing, is always make sure your gauge is fused off with no bigger then a 1 amp fuse.



Kev

 

[willyslover]

thanks kev. . my gauges are SPA and the issue is the thin probe wen bent a slight bit to clear is breaks the internal insulation and goes to a direct short... guess we learn every day



sooo there ya are Gizmo. . several ways to check

 

[ToolManTimTaylor]

Originally posted by Gizmo 007

I've had worse.



Again, THANKS!

there is

 

[tractorface]

You can test your thermocouple with a multi-meter. Your Pyrometer is simply measuring the resistance of the probe. Type K probes use either Alumel or Chromel thermoelement material so its hard for me to say what the resistance of your probe should be at a given temp. Anyway you can check the resistance at room temp and call the manufacturer, they should be able to tell you what the Resistance should be.

www.omega.com is a good source for Thermocouple information



http://www.omega.com/temperature/Z/pdf/z049-050.pdf



Above is a link to Omega and a technical section on Thermocouples.

Good Luck

 

[Fish On]

If you have the old gauge that connects to a brain box first then it could be a gauge problem. I went round and round trying to figure out why my egt guage kept acting up. Mine ultralite was doing the same thing as yours. Needle bouncing etc. Anyway, after a call to autometer they replaced the old style gauge with a new gauge that the probe connects directly to gauge. Free of charge. It has been in for 7 months and has worked great. Hope you figure out your prob.

 

[Sregorb]

Had the exact same problem a few months ago. A quick trip down the road with the wires from the thermocouple on a multimeter sealed the fault as the probe. Swapped out by Autometer without sending the whole system to them (which is what they originally wanted).

If you can, testing the voltage from the probe during hot runs and comparing with the thermocouple expected returns can save alot of hassle.

Also, be careful not to crush the probe when replacing. they said the biggest problem has been people over tightening the probe mount and crushing the tube into the wires... .



Brian

 

[KFaulk]

Check your ground wire before you yank everything out. Always do the simple (think cheapest) things first.

 

[illflem]

Originally posted by tractorface

You can test your thermocouple with a multi-meter. Your Pyrometer is simply measuring the resistance of the probe.

You sure about that? I always thought thermocouples put out voltage, thermistors change resistance with temp change.

 

[Gizmo 007]

K-type thermocouples produce a very low amount of voltage (mine does anyway). Tested my probe today, it's intermitantly shorted to ground. Glad I found the problem, thanks for steering me there guys! I found he ticket from O'Reillys where I bought it... It happens to have lifetime warranty . Gonna exchange it.



ToolMan, I sucked a nut through both turbos (dual turbos) a month or so ago, that was worse. Cratered both compressor wheels and a shaft. That sucked . I've since beat the crap outta the guy who forgot to tighten it... me.

 

[Sregorb]

Gizmo-Glad you found it! Lifetime warranty huh? O'reillys huh? Might have to start doing business with them.....



Yes, thermocouples are voltage and thermistors are resistance... .



Ouch on the twin turbo trashing!



Brian

 

[tractorface]

I am quite sure that the resistance changes as the temperature changes. The link below shows some tables that may be useful.



http://www.omega.com/temperature/Z/pdf/z049-050.pdf



I was incorrect about the meter reading resistance, it does read voltage. My Bad.

You should still be able to check the resistance of the probe and determine if it is bad or not.

I have done this with an oven probe in the past (Now that I think about it maybe it was a thermister)... . I'll run out to the shop and see if I can find a Thermocouple or two to test. I need to brush up on my temperature measurement theory a little. I'll post back if I can find one and check it out. Current loops are more my speed, sorry.

Thanks for the heads up!



I could not find any TC's in the shop so I did some reading. Forget it, they do use resistance readings as a Diagnostic tool but not like I thought. You are on your own. The link above will provide some good reading on the subject of TC's, I know I have a better understanding of how they work now. Again my bad, these little guys are more complicated than I thought.

Good Luck!

 

[illflem]

Thermocouples work because two different metals, I think nickel and copper, joined together generate different voltages according to temperature, your gauge is just a very sensitive voltmeter.

Because of this property of dissimilar metals generating voltage it's important that any wire splices or switches added to the pyro circuit be of the same material otherwise the reading can be incorrect.

If I'm not mistaken thermistors can only take up to around 800F before they fry.