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Dermodad Samba Member
Joined: January 14, 2010 Posts: 28 Location: Texarkana, TX
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Posted: Sat Dec 08, 2018 2:51 pm Post subject: Fuel gauge calibration |
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71 flat windshield superbeetle. My original sender unit was bad, but gauge itself would freely register full when sender unit bypassed. So I bought a new sending unit from JBugs, and an exciter while I was at it. Bench tested the new sending unit and it seemed good at both extremes (10/72 ohms). Once installed (with old exciter) it registers full at 10 gallons (great!),but drops precipitously so that at 3/4 full the gauge says 1/4. I have not trusted it enough to run to near empty so see what happens.
I've taken the sending unit out and played with again; and changed the exciter. No change in results. Installed, the sending unit reads about 25 olms with about 7.5 gallons on board.
I called JBugs techs and they suggested I needed to "calibrate my gauge to the new sending unit" by altering adjuster screws in the gauge itself. Most threads here just talk about bending the sending unit arms as adjustment. I don't see anything about changing the gauge calibration. I am a little wary of breaking into the gauge, although it doesn't look hard.
Anybody got any ideas on this?
Anybody got any insight into this problem? |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11740 Location: Redding, CA
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Posted: Sat Dec 08, 2018 4:22 pm Post subject: Re: Fuel gauge calibration |
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I think you got a bum sender.
I just read that someone else had problems with Jbug’s sender, which was a Dansk. They sent it back and got a Mexican one from Rock Auot. Then it worked fine.
You should NOT have to calibrate your gauge.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien
Last edited by Tim Donahoe on Sat Dec 08, 2018 6:03 pm; edited 1 time in total |
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390nellie Samba Member
Joined: May 28, 2017 Posts: 138 Location: Westfield Massachusetts
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Posted: Sat Dec 08, 2018 4:24 pm Post subject: Re: Fuel gauge calibration |
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I have the exact same problem. Purchased and installed a new tank, sending unit and vibrator from Jbugs. Fill the tank needle goes to full. When needle touches the first reserve line there is nearly 1/2 tank remaining.
I am reluctant to adjust the gauge. I'm afraid adjusting one end of the spectrum may only throw off the other.
If you do adjust the gauge please let us know the outcome. |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Sat Dec 08, 2018 4:52 pm Post subject: Re: Fuel gauge calibration |
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Haw, I am right in the middle of this issue.
I have about 5 pages of tech notes related to the gauges currently being sold by everyone. Along with the Vibrator/regulator. I have 3 regulators and 4 gauges that I have purchased for testing.
As of now I am not ready to tell the whole tale but in a couple of weeks if I have time I will have some good information to post.
As of now I will say that calibrating the gauge is not an easy task and will not provide the results you will get. There are two adjustments for the gauge. The one you can see from the rear of the gauge is named Zero adjust and is a very fine adjustment. There is another one requires you to remove the plastic rear cover! It is named Range (by someone). That is the one that will move the needle quite a bit but it does not increase the travel of the needle. So if you say you want to move the needle more towards full then when the tank is empty it will read way above empty, probably around 1/4 to 1/2 tank hahahaa. If you do not have fine feel with your hands and a tool to work the teeth of the adjustment you should not attempt to adjust unless you are willing to purchase another meter in the case you damage the gauge.
Here is another problem: The non oem vibrator is not a vibrator circuit. It is a Zener 5.1 vdc regulator with a 5watt 12vdc lightbulb for a load. It does regulate the voltage pretty steady from 13vdc down to about 9vdc... The 5volts will vary a bit... .1- .3 vdc when the ignition is on, low battery charged battery, lights on and off.
I am waiting to pull a true vibrator out of my Baja to measure the actual performance.I also have a bud that has a couple laying around. OEM vibrators switch the 12vdc on and off to regulate the voltage of around 5.1 to the meter. I believe the actual means voltage will be higher than 5.1 vdc... The higher the voltage the wider the meter swing.. Problem is as the actual voltage goes up the current will increase... The question is how much current will the VERY FINE wire that is wrapped around the meters BI metal arm that bends from the heat generated by the current handle until it burns up? This is where I am at as of now.
I have opened one up to see how it is made and how it works.
Here is my Fuel Gauge project.
[/img] _________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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TDCTDI Samba Advocatus Diaboli
Joined: August 31, 2013 Posts: 12860 Location: North Carolina
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Posted: Sat Dec 08, 2018 5:16 pm Post subject: Re: Fuel gauge calibration |
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Leave the gauge alone!
Get a one gallon gas can & fill it. Run the car until empty, pour the contents of the gas can into the tank, remove the sender & bend the float arm in the middle (so you’re not bending the arm inside the sender portion) & re-install the sender. Make adjustments until the gauge reads to the top of the reserve line. _________________ Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Sat Dec 08, 2018 5:45 pm Post subject: Re: Fuel gauge calibration |
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Here are a couple of pictures showing an OEM vibrator v/s the non OEM vibrator/regulator being sold by everyone.
Picture of the NON-OEM gauge. Note the light bulb. 12vdc 5 watt.
This is the back side of an OEM VDO vibrator.
Note the little black painted circle. That is a seal to lock the... WAIT for it!!!
A factory adjustment to calibrate the meter... It changes the on off of the bimetal lever for the contacts.
I have not had time to test a good OEM VDO vibrator to determine the actual average voltage... So hang tight and I should have some information..
This is the guts of an OEM vibrator. You can see the coil of wire that heats the bimetal arm... From reading it is suppose to switch on and off about 3 times a second... I have not verified that as a fact.
This picture shows the 2 adjustments for the needle.The top left one is the one that is not able to adjust without removing the plastic back of the meter.
Here you can see the fine wire of the bimetal lever.
_________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Sat Dec 08, 2018 6:16 pm Post subject: Re: Fuel gauge calibration |
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Tim Donahoe wrote: |
I think you got a bum sender.
I just read that someone else had problems with Jbug’s sender, which was a Dansk. They sent it back and got a Mexican one from Rock Auot. Then it worked fine.
You should NOT have to calibrate your gauge.
Tim |
3 different gauges, 2 sending units, 3 regulators/vibrators .. then bench testing with fixed voltages and resistances........
Meters will not show full range and not one meter shows the same...But they all show about 1/2 tank when full.
At this point I have not tested any of the gauges with an OEM Vibrator.
10 ohms fixed or 10-11 ohms from a sending unit.
I have a feeling that many folks are just living with the situation.
Jim _________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11740 Location: Redding, CA
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Posted: Sat Dec 08, 2018 6:20 pm Post subject: Re: Fuel gauge calibration |
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I will never install another OEM vibrator. When they fail, they allow a full twelve volts into your gauge, which will fry your gauge (you’ll see the smoke when this happens). Besides, most OEM vibrators that still work have been doing so for decades. Sooner or later, that old sucker will fail. Not only can this burn out your gauge, it can also burn out the rheostat in your sender.
However, when the new “non-vibrator” vibrator fails, it simply stops the flow of voltage altogether, thus saving your ultra thin gauge wires and sender rheostat.
Be careful, however. There are good new-type vibrators out there. These have a small but obvious hump on the back. This type is more expensive than the cheapies which look pretty much the same—black plastic. But, from what I understand, they lack a zenor diode, so no hump in the back side.
It’s been awhile since I checked these out at any vendors, so for all I know, they may not even offer the cheapies, anymore.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Sat Dec 08, 2018 6:39 pm Post subject: Re: Fuel gauge calibration |
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Tim Donahoe wrote: |
I will never install another OEM vibrator. When they fail, they allow a full twelve volts into your gauge, which will fry your gauge (you’ll see the smoke when this happens). Besides, most OEM vibrators that still work have been doing so for decades. Sooner or later, that old sucker will fail. Not only can this burn out your gauge, it can also burn out the rheostat in your sender.
However, when the new “non-vibrator” vibrator fails, it simply stops the flow of voltage altogether, thus saving your ultra thin gauge wires and sender rheostat.
Be careful, however. There are good new-type vibrators out there. These have a small but obvious hump on the back. This type is more expensive than the cheapies which look pretty much the same—black plastic. But, from what I understand, they lack a zenor diode, so no hump in the back side.
It’s been awhile since I checked these out at any vendors, so for all I know, they may not even offer the cheapies, anymore.
Tim |
Agree about the OEM Vibrators eating the gauge...hahahaaaa.
Agree about the Zener diode. I have spelled that out.
What I need to know is what the true RMS voltage is from a working Vibrator.
I can make the meters work full scale by increasing the voltage of the meter where the vibrator attaches to the meter. I have linearly increased that voltage but have not established what voltage will work without stressing the meter bimetal wire... Measuring the current both through the Zener and to the meter.
We know that when we turn on the ignition an OEM meter and OEM vibrator will make the needle rapidly move to what ever the sending unit is positioned to...
The Zener diode type vibrator/regulator the needle takes over 10 seconds to make it clear to full...hahahaa
I am hopeful that a conclusion can be reached but to what outcome?
I would like to see a simple fix but at this point it might be simple for me but not for the average VW guy.
As a note, when the Zener fails it shorts out...The light bulb becomes pretty bright.... Yep saves the meter. A common method for circuit protection with switcher power supplies.
Jim _________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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glutamodo The Android
Joined: July 13, 2004 Posts: 26325 Location: Douglas, WY
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Posted: Sun Dec 09, 2018 6:28 am Post subject: Re: Fuel gauge calibration |
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Blue69Baja wrote: |
Here are a couple of pictures showing an OEM vibrator v/s the non OEM vibrator/regulator being sold by everyone. |
Just one clarification. The 113957099A Zener Diode style voltage stabilizer WAS AN OEM part, at one time, they were made by VDO for VW! It was used to reduce radio interference that the vibrating style can cause. Here's one made in Germany 9/79:
As mentioned above, I also don't care for the very slow response time when the Zener diode style is fitted. _________________ Andy T.
IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox. |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Sun Dec 09, 2018 6:45 pm Post subject: Re: Fuel gauge calibration |
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Andy thanks for your input. Did not know that they went with the Zener diode regulator... Can you get a read on that Zener... 1nXXXX or whatever number style... I would like to know what voltage they were using if possible.
Jim. _________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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glutamodo The Android
Joined: July 13, 2004 Posts: 26325 Location: Douglas, WY
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Posted: Sun Dec 09, 2018 11:06 pm Post subject: Re: Fuel gauge calibration |
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It's been a long time since I played with a German one - that photo above wat taken at the VW parts/service shop I used to work at, we had a couple of them mixed in with the vibrator style. (but I'm sitting about 170 miles away from there as I type this)
The old Haynes 1200 service manual - the original version that was 1200-centric, in its supplement chapters for years newer than 1966, had this to say - but no real values given. I'd have to dig into my boxes of stored books to access the diagrams mentioned here.
_________________ Andy T.
IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox. |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Sun Dec 09, 2018 11:20 pm Post subject: Re: Fuel gauge calibration |
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Haw Andy, that would be the way to troubleshoot the current non OEM vibrator types currently avail. The diode shorts thus protecting the meter!
The bulb will get pretty warm then too.
Thanks for posting the document.
Jim _________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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runamoc Samba Member
Joined: June 19, 2006 Posts: 5601 Location: 37.5N 77.1W
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Posted: Mon Dec 10, 2018 10:04 am Post subject: Re: Fuel gauge calibration |
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Quote: |
What I need to know is what the true RMS voltage is from a working Vibrator. |
With the 'transition' between on and off measured in seconds, it is more of a square wave of 20 cycles per minute. (3sec) Then decide what is more important. Empty or full.
For me, it's where empty is. Did what TDCTDI did, run out of gas someplace safe. Poured the gallon of gas in and drove it to the gas station noting the needle location. (Didn't take sending unit out though) When it gets near that location on the gauge again it's time for some gas. I consider a fill up at 5 sometimes 6 gallons even. Makes it easier to calculate MPG _________________ Daily driver: '69 Baja owned 44 yrs - Plan B: '81 Rabbit Diesel LS Deluxe - Plan C: '72 Ghia
Yard Art: 2 Sandrails
Outback: '69 Ghia - '68,'69,'70,'72 Beetle - '84 Scirocco, GTI - Pair of '02 Golfs-
VW Wiring = It's just wires |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Mon Dec 10, 2018 10:16 am Post subject: Re: Fuel gauge calibration |
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runamoc wrote: |
Quote: |
What I need to know is what the true RMS voltage is from a working Vibrator. |
With the 'transition' between on and off measured in seconds, it is more of a square wave of 20 cycles per minute. (3sec) Then decide what is more important. Empty or full.
For me, it's where empty is. Did what TDCTDI did, run out of gas someplace safe. Poured the gallon of gas in and drove it to the gas station noting the needle location. (Didn't take sending unit out though) When it gets near that location on the gauge again it's time for some gas. I consider a fill up at 5 sometimes 6 gallons even. Makes it easier to calculate MPG |
Yep that is one way to deal with the issue. Or fill up every 100 miles.
It would be nice for us to have a regulator that can be adjusted to the gauge...
Looking into buck regulators for a final solution. But before I do this I need to know what the actual safe voltage/current range of the gauge is.
Jim _________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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glutamodo The Android
Joined: July 13, 2004 Posts: 26325 Location: Douglas, WY
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Posted: Mon Dec 10, 2018 12:25 pm Post subject: Re: Fuel gauge calibration |
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While I have a long history of mucking about with mechanical sending units, but as far as electrical ones, I've never gone and bent the arm. Never needed to. Okay, the gauge does have a factory-level adjustment, I have =very slightly= played with that before but not much. I've got my Baja (with a 1968 Speedometer, and later than that fuel gauge but I changed the faceplate out to keep with the 1968 motif- also, using a German replacement VDO tank unit) set up so I can trust the lower fuel level readings in a meaningful way.
A classic link for the fuel gauge: http://www.speedyjim.net/htm/fuel_ga.htm _________________ Andy T.
IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox. |
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Blue69Baja Samba Member
Joined: September 04, 2008 Posts: 1065 Location: Fair Oaks
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Posted: Mon Dec 10, 2018 12:39 pm Post subject: Re: Fuel gauge calibration |
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glutamodo wrote: |
While I have a long history of mucking about with mechanical sending units, but as far as electrical ones, I've never gone and bent the arm. Never needed to. Okay, the gauge does have a factory-level adjustment, I have =very slightly= played with that before but not much. I've got my Baja (with a 1968 Speedometer, and later than that fuel gauge but I changed the faceplate out to keep with the 1968 motif- also, using a German replacement VDO tank unit) set up so I can trust the lower fuel level readings in a meaningful way.
A classic link for the fuel gauge: http://www.speedyjim.net/htm/fuel_ga.htm |
Have read that link and others about the gauge and other non VW Beetle. Many use the same design.
I have performed the adjustments from the rear of the gauge.... As I said, " adjusting the range one does move the needle quite a bit but does not increase the travel. That is what we need from what I have discovered. I have applied near 6vdc to the meter and it will travel almost from full to empty.
Sure would be nice to have an easily adjustable meter in my opinion.
The VDO and the non OEM gauge does not make it easy to get to the Range adjustment of the gauge.
Jim _________________ 69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original.. |
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glutamodo The Android
Joined: July 13, 2004 Posts: 26325 Location: Douglas, WY
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Posted: Tue Dec 11, 2018 2:03 pm Post subject: Re: Fuel gauge calibration |
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I still dislike calling it "non-OEM" because, well, it was OEM. Hell, they both had VW part numbers! - 113957099 and 113957099A.
(I would rather call them "Vibrator" and "Zener diode" styles. ) _________________ Andy T.
IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox. |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11740 Location: Redding, CA
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Posted: Tue Dec 11, 2018 4:35 pm Post subject: Re: Fuel gauge calibration |
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Well, everybody knows what the vibrator is, but a zenor diode “style” doesn’t quite cut it. Zenor diode style ... what? It’s not a zenor style vibrator, because it doesn’t vibrate? So, do we call it a zenor style “gauge regulator”? Maybe that’s the ticket.
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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glutamodo The Android
Joined: July 13, 2004 Posts: 26325 Location: Douglas, WY
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Posted: Tue Dec 11, 2018 4:52 pm Post subject: Re: Fuel gauge calibration |
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Well one is electro-mechanical and the other solid-state electronic. _________________ Andy T.
IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox. |
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