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matronics(at)bob.brennan.
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 Posted: Thu Sep 25, 2008 1:08 pm Post subject: Water temperature guage |
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Hi all - my water temperature gauge is suddenly swinging full scale on a cold engine.
Two things recently that could affect it:
1. I had the dash off to replace the lord mounts, so 1st thing to check was open wires - nope.
2. On most recent flight the gauge went well into the red after taxi and was erratic. Thinking "better check coolant level" I did, when cold, and it was full to the top as well as a few inches in the overflow.
The gauge has a good ground, a good 12+vdc, and 6.87vdc on the sensor lead on a cold engine and 60f day.
I guess what I need to know is: should 6.87v pin the needle(hard!) on full scale? ie does anyone know what is the normal voltage range of the sensor, as in - does 6.87vdc = 60f?
There are no manufacturer's markings on the gauge or sensor that I can find.
Thanks in advance for any info or where to look.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
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matronics(at)bob.brennan.
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| Posted: Thu Sep 25, 2008 3:32 pm Post subject: Water temperature guage |
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Hi all - my water temperature gauge is suddenly swinging full scale on a cold engine.
Two things recently that could affect it:
1. I had the dash off to replace the lord mounts, so 1st thing to check was open wires - nope.
2. On most recent flight the gauge went well into the red after taxi and was erratic. Thinking "better check coolant level" I did, when cold, and it was full to the top as well as a few inches in the overflow.
The gauge has a good ground, a good 12+vdc, and 6.87vdc on the sensor lead on a cold engine and 60f day.
I guess what I need to know is: should 6.87v pin the needle(hard!) on full scale? ie does anyone know what is the normal voltage range of the sensor, as in - does 6.87vdc = 60f?
There are no manufacturer's markings on the gauge or sensor that I can find.
Thanks in advance for any info or where to look.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
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mikeperkins
Joined: 22 May 2007
Posts: 123
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| Posted: Fri Sep 26, 2008 10:22 am Post subject: Water temperature guage |
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Water temperature gauges are usually “amplified” gauges, meaning they use ship’s power to run a small amplifier that multiplies the thermocouple’s signal many times so that it can produce a reading on the meter. (EGT thermocouples run many times hotter and therefore produce more voltage, so they often don’t use amplifiers but have direct-reading meters instead.) On an amplified gauge, make sure the +V and ground to it have good connections.
In my experience, however, on any kind of gauge, the sensor goes bad much more often than the gauge itself because of the environment in which it lives. The voltage on sensors is often a “differential” voltage, meaning it’s the difference between the two wires from the sensor that the gauge reads, not the voltage as referenced from ground. Some sensors have the amplifier built into them, and they have three or four wires, in which case you have to contact the manufacturer for the pinouts and troubleshooting procedure.
(If I knew you had a Westach gauge like mine, I’d run out to the airport and take some measurements for you.)
Mike Perkins
[quote][b]
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matronics(at)bob.brennan.
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| Posted: Fri Sep 26, 2008 10:59 am Post subject: Water temperature guage |
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Hi Mike,
Further research:
The gauge is identical to the Westach K36X pictured on ACS: http://www.aircraftspruce.com/catalog/inpages/westfaa4.php
The sensor appears to be supplied with the Rotax engine: http://www.aircraftspruce.com/catalog/inpages/umawatertemp1.php
I found a schematic in the build sheets that matched the wiring: very simple - 12vdc to one terminal, ground to another, the third to the sensor which goes via very light gauge twisted pair to ground, so it must be a simple thermistor.
My line of attack is to jumper the +12 and ground wires via a good wire in case of breakage in the existing ones, and then move the sensor ground to the ground on the instrument itself, suspecting ground looping. The wiring is a real rats' nest and I did move a few grounds (not that one) to re-connect a low-fuel sensor that had been disconnected before I bought the plane. Come to think of it - I will first disconnect the low fuel sensor, maybe the guy before me cut it out *because* it caused the temp gauge to misread!
Mustn't forget my cardinal rule - always undo any changes done since it worked - first.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Perkins, Mike
Sent: 26 September 2008 2:22 pm
To: kitfox-list(at)matronics.com
Subject: Re: Water temperature guage
Water temperature gauges are usually “amplified” gauges, meaning they use ship’s power to run a small amplifier that multiplies the thermocouple’s signal many times so that it can produce a reading on the meter. (EGT thermocouples run many times hotter and therefore produce more voltage, so they often don’t use amplifiers but have direct-reading meters instead.) On an amplified gauge, make sure the +V and ground to it have good connections.
In my experience, however, on any kind of gauge, the sensor goes bad much more often than the gauge itself because of the environment in which it lives. The voltage on sensors is often a “differential” voltage, meaning it’s the difference between the two wires from the sensor that the gauge reads, not the voltage as referenced from ground. Some sensors have the amplifier built into them, and they have three or four wires, in which case you have to contact the manufacturer for the pinouts and troubleshooting procedure.
(If I knew you had a Westach gauge like mine, I’d run out to the airport and take some measurements for you.)
Mike Perkins
[quote]
href="http://www.matronics.com/Navigator?Kitfox-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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matronics(at)bob.brennan.
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| Posted: Sat Sep 27, 2008 6:00 am Post subject: Water temperature guage |
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> (If I knew you had a Westach gauge like mine, I’d run out to the airport and take some measurements for you.)
Mike - if you get a chance to make a measurement that would save me a coin toss of spending $118 for a new gauge vs $68 for a new sensor, one of which would be wasted if it were not the cause. It's Murphy's Law of Averages = 50/50 chance of getting it right, 90% chance of getting it wrong 
My setup is currently reading 6.87v between the ground pin and the sensor pin on the gauge, on a 60f day with the engine stone cold. I can't find any data sheets on either the gauge or sensor correlating voltage to temperature. If your reading is close to mine then it is the gauge, if it is way lower then it is the sensor. I still have yet to check integrity wires too.
Thanks in advance,
bob
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Perkins, Mike
Sent: 26 September 2008 2:22 pm
To: kitfox-list(at)matronics.com
Subject: Re: Water temperature guage
Water temperature gauges are usually “amplified” gauges, meaning they use ship’s power to run a small amplifier that multiplies the thermocouple’s signal many times so that it can produce a reading on the meter. (EGT thermocouples run many times hotter and therefore produce more voltage, so they often don’t use amplifiers but have direct-reading meters instead.) On an amplified gauge, make sure the +V and ground to it have good connections.
In my experience, however, on any kind of gauge, the sensor goes bad much more often than the gauge itself because of the environment in which it lives. The voltage on sensors is often a “differential” voltage, meaning it’s the difference between the two wires from the sensor that the gauge reads, not the voltage as referenced from ground. Some sensors have the amplifier built into them, and they have three or four wires, in which case you have to contact the manufacturer for the pinouts and troubleshooting procedure.
(If I knew you had a Westach gauge like mine, I’d run out to the airport and take some measurements for you.)
Mike Perkins
[quote]
href="http://www.matronics.com/Navigator?Kitfox-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Mon Sep 29, 2008 5:00 am Post subject: Water temperature guage |
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Those sensors typically use a coil of nickel alloy to sense temperature. Resistance increases with temperature. If the seal on the probe is leaking fluid into the coil it will go off scale. Check the probe by checking its resistance with a good VOM while immersing it into a container of cold water... As you heat the water the resistance should increase.
[img]cid:image001.jpg(at)01C9221E.1FF5DE60[/img]
Noel Loveys
Campbellton, NL, Canada
CDN AME intern, PP-Rec
C-FINB, Kitfox III-A
582 B box, Ivo IFA, Aerocet 1100 floats
[url=noelloveys(at)yahoo.ca]noelloveys(at)yahoo.ca[/url]
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Bob Brennan
Sent: Thursday, September 25, 2008 6:37 PM
To: kitfox-list(at)matronics.com
Subject: Water temperature guage
Hi all - my water temperature gauge is suddenly swinging full scale on a cold engine.
Two things recently that could affect it:
1. I had the dash off to replace the lord mounts, so 1st thing to check was open wires - nope.
2. On most recent flight the gauge went well into the red after taxi and was erratic. Thinking "better check coolant level" I did, when cold, and it was full to the top as well as a few inches in the overflow.
The gauge has a good ground, a good 12+vdc, and 6.87vdc on the sensor lead on a cold engine and 60f day.
I guess what I need to know is: should 6.87v pin the needle(hard!) on full scale? ie does anyone know what is the normal voltage range of the sensor, as in - does 6.87vdc = 60f?
There are no manufacturer's markings on the gauge or sensor that I can find.
Thanks in advance for any info or where to look.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
| Quote: | | http://www.matronics.com/Navigator?Kitfox-List |
0123456789
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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matronics(at)bob.brennan.
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| Posted: Mon Sep 29, 2008 7:03 am Post subject: Water temperature guage |
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Excellent suggestion Noel, I will try that. I think I saw somewhere that the range on those sensors is 20-200 ohms, but a decent data sheet on either the Westach gauge or the sensor could speed things up considerably.
Mike Perkins has promised to make some measurements on his similar setup this week and I will try to contact Westach as well.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Noel Loveys
Sent: 29 September 2008 8:59 am
To: kitfox-list(at)matronics.com
Subject: RE: Water temperature guage
Those sensors typically use a coil of nickel alloy to sense temperature. Resistance increases with temperature. If the seal on the probe is leaking fluid into the coil it will go off scale. Check the probe by checking its resistance with a good VOM while immersing it into a container of cold water... As you heat the water the resistance should increase.
[img]cid:140255514(at)29092008-323E[/img]
Noel Loveys
Campbellton, NL, Canada
CDN AME intern, PP-Rec
C-FINB, Kitfox III-A
582 B box, Ivo IFA, Aerocet 1100 floats
[url=noelloveys(at)yahoo.ca]noelloveys(at)yahoo.ca[/url]
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Bob Brennan
Sent: Thursday, September 25, 2008 6:37 PM
To: kitfox-list(at)matronics.com
Subject: Water temperature guage
Hi all - my water temperature gauge is suddenly swinging full scale on a cold engine.
Two things recently that could affect it:
1. I had the dash off to replace the lord mounts, so 1st thing to check was open wires - nope.
2. On most recent flight the gauge went well into the red after taxi and was erratic. Thinking "better check coolant level" I did, when cold, and it was full to the top as well as a few inches in the overflow.
The gauge has a good ground, a good 12+vdc, and 6.87vdc on the sensor lead on a cold engine and 60f day.
I guess what I need to know is: should 6.87v pin the needle(hard!) on full scale? ie does anyone know what is the normal voltage range of the sensor, as in - does 6.87vdc = 60f?
There are no manufacturer's markings on the gauge or sensor that I can find.
Thanks in advance for any info or where to look.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
| Quote: | | http://www.matronics.com/Navigator?Kitfox-List |
0123456789
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
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7.29 KB |
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3953 Time(s) |
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matronics(at)bob.brennan.
Guest
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| Posted: Mon Sep 29, 2008 7:33 am Post subject: Water temperature guage |
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From Westach (*really* fast reply!):
You need to check with an Ohm meter ~ disconnect the sender from the gauge ~ here are the resistance values for the temp sender:
50 deg. F = 5,970 ohms
60 deg. F = 4,600 ohms
70 deg. F = 3570 ohms
80 deg. F = 2,780 ohms
90 deg. F = 2, 190ohms 100 deg. F = 1740 ohms
210 deg. F = 210 ohms ~ boiling water
212 deg. F = 212 ohms
Also check to make sure you have a good ground and that it didn't become disconnected ( this cause gauges to go full scalle)
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Bob Brennan
Sent: 29 September 2008 10:59 am
To: kitfox-list(at)matronics.com
Subject: RE: Water temperature guage
Excellent suggestion Noel, I will try that. I think I saw somewhere that the range on those sensors is 20-200 ohms, but a decent data sheet on either the Westach gauge or the sensor could speed things up considerably.
Mike Perkins has promised to make some measurements on his similar setup this week and I will try to contact Westach as well.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Noel Loveys
Sent: 29 September 2008 8:59 am
To: kitfox-list(at)matronics.com
Subject: RE: Water temperature guage
Those sensors typically use a coil of nickel alloy to sense temperature. Resistance increases with temperature. If the seal on the probe is leaking fluid into the coil it will go off scale. Check the probe by checking its resistance with a good VOM while immersing it into a container of cold water... As you heat the water the resistance should increase.
[img]cid:234143015(at)29092008-3245[/img]
Noel Loveys
Campbellton, NL, Canada
CDN AME intern, PP-Rec
C-FINB, Kitfox III-A
582 B box, Ivo IFA, Aerocet 1100 floats
[url=noelloveys(at)yahoo.ca]noelloveys(at)yahoo.ca[/url]
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Bob Brennan
Sent: Thursday, September 25, 2008 6:37 PM
To: kitfox-list(at)matronics.com
Subject: Water temperature guage
Hi all - my water temperature gauge is suddenly swinging full scale on a cold engine.
Two things recently that could affect it:
1. I had the dash off to replace the lord mounts, so 1st thing to check was open wires - nope.
2. On most recent flight the gauge went well into the red after taxi and was erratic. Thinking "better check coolant level" I did, when cold, and it was full to the top as well as a few inches in the overflow.
The gauge has a good ground, a good 12+vdc, and 6.87vdc on the sensor lead on a cold engine and 60f day.
I guess what I need to know is: should 6.87v pin the needle(hard!) on full scale? ie does anyone know what is the normal voltage range of the sensor, as in - does 6.87vdc = 60f?
There are no manufacturer's markings on the gauge or sensor that I can find.
Thanks in advance for any info or where to look.
Bob Brennan - N717GB
1991 UK Model 2 ELSA Kitfox
Rotax 582 with 3 blade prop
Wrightsville Pa
| Quote: | | http://www.matronics.com/Navigator?Kitfox-List |
0123456789
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kitfox-List |
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| Viewed: |
3953 Time(s) |
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