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Fuel Sender Diagnosis/Repair


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#26 Dangerous

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Posted 06 September 2006 - 11:35 AM

Hi Guys.

Dangerous said:- "the mid scale resistor should be roughly half way between the 10 ohm and 75 ohm range of the gauge, and the nearest preferred value would be a 33 ohm resistor. "

This is not correct, the thermister (sender) is non-linear. A 33 ohm resistor will result in a gauge reading closer to a 1/3 scale.



Dr Terry.

Hey Doc, I PM'd you a question about this - just wondering if you got it?

#27 caseyo69

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Posted 15 September 2006 - 01:10 AM

gday yella SLuR would these tips help me get my HQ's guage working or not :blink: coz it doesnt work and it is a ute :D

#28 Yella-5000

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Posted 15 September 2006 - 01:46 PM

Should do, only difference will be the different resistance range for the HQ guage. I think the HQ guages can cope with 0 resistance, whereas the Torrie ones can't. Best just to check the guage resistance range in the HQ manual before proceeding.

#29 Tiny

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Posted 15 September 2006 - 02:16 PM

TO the best of my knowledge the Ohms range of the HQ guage is 0-30 Ohms ( cant rmeber which reads full though...)..

They changed this because 0 ohms is also an open circuit so any open circuit ( damaged sender) full cause full deflection and cooking of the guage!

Cheers.

#30 Dr Terry

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Posted 15 September 2006 - 03:22 PM

Hi Guys.

An open circuit is not 0 ohms. A short circuit approaches 0 ohms, but an open circuit is infinity, or millions of ohms, in practise anyway. When a magnetic gauge sender goes open circuit & the gauge sits at full scale, it will not 'burn out' as there is no heating element as such.

The HQ fuel gauges come in 2 varieties, like many items in the HQ series they changed spec in early '73. The '71 & '72 cars use a magnetic gauge, like LC/LJ & the sender reads 0, 15 & 30 ohms for empty, half & full. The early '73 onwards used a thermal gauge with the same specs as LH/LX Toranas (& HJ/HX/HZ) & the sender is the reverse non-linear 73, 25 & 10 for empty, half & full.

The above applies to HQ fuel gauges only, their oil & temp gauges remain magnetic for the whole HQ model run & have the same specs as LC/LJ oil & temp gauges.

I apologise for sounding sounding like a Holden 'nerd'.

Dr Terry.

#31 Tiny

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Posted 15 September 2006 - 03:35 PM

hehe Thank GOD we have some Holden NERDS on here Dr terry!! Otherwise false information like i gave would run rife!!

Thanks for the correction!!

#32 caseyo69

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Posted 15 September 2006 - 06:36 PM

Thanks for the quick response yella SLuR much appreciated :spoton:

#33 Dangerous

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Posted 15 September 2006 - 07:18 PM

I apologise for sounding sounding like a Holden 'nerd'.

Dr Terry.

"Nerd" away Doc, it's all good valuable info! :spoton:

#34 Yella-5000

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Posted 15 September 2006 - 07:33 PM

Yeah, I knew they were different, not that different though! Good info.

You raise a good point though there Tiny. Open circuit will read 1 on the multimeter, the equivalent of infinite, or out of range.

Edited by Yella SLuR, 15 September 2006 - 07:34 PM.


#35 jap-xu1

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Posted 16 September 2007 - 04:12 PM

can anyone confirm this for me.
there are 4 different fuel level gauges available,each has a different empty and full rating.

which one applies to a lj sender?

empty 0 full 90
empty 73 full 10
empty 240 full 33
empty 16 full 158

#36 jap-xu1

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Posted 16 September 2007 - 04:32 PM

my sender is giving me from about 2.6 at empty to 14.8 at full
i have the multimeter set on 200.

im pretty confused and need to order my gauges asap so any help would be much appreciated

#37 Dr Terry

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Posted 16 September 2007 - 04:41 PM

Hi jap-xu1

Unfortunately it's not one of the ones that you've listed.

ALL early Holdens up to TA Torana & '72 HQ use a fuel sender that is 0 ohms empty & 30 ohms full.

Dr Terry.

#38 jap-xu1

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Posted 16 September 2007 - 04:54 PM

what do you reckon of mine only going upto 15?
its only going to read 1/2 at best i know but what can i do to fix it?

can you still buy the senders genuine?

also my car is a 73 lj and it has am price engineering tank.
the sender is a black plastic float type.

my bros is a 69 lc and his reads 10 to 40 and his has a cork type float

Edited by jap-xu1, 16 September 2007 - 04:56 PM.


#39 marko1au

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Posted 08 December 2007 - 02:14 PM

well you have got me totally confused after reading this post and on reading an earlier one on this subject :<_<: i was looking at installing after market fuel gauge into my lx. one of the manufactures quotes 10 ohms empty and 72 ohms full so i thought i would use this site to see if i could fit this gauge into my car with ohms quoted. now my question is which of the posts is correct, one quotes 10 ohms empty and 68-72 ohms full. then another post quotes 10 ohms full and 68 -72 ohms empty please which one is correct

#40 Dr Terry

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Posted 09 December 2007 - 10:16 AM

Hi marko1au

LH/LX fuel sender is 73 ohms empty & 10 ohms full.

Dr Terry

#41 marko1au

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Posted 09 December 2007 - 07:13 PM

thankyou very much for the correct information

#42 Bart

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Posted 01 February 2009 - 11:52 PM

Hey Dr Terry
I have an LJ Torana with GTR dash, and the gauges, fuel, temp, oil pressure, go straight to full
I read somewhere its due to the voltage regulator short circuit??
Can the voltage regulator be replaced with a 12v reg from dick smith?
Thanks
Bart

#43 LHSL

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Posted 25 November 2012 - 09:14 PM

Hi Everyone,
I took out my LH fuel tank to strip paint off and paint. In the process I didn't realise the float fell off the sender unit.
Once the tank was re-installed the fuel gauge was playing up and showed well over full when full. To cut to the chase I lived with it and you know what happened I blew the volatge regulator. This in turn blew up both the fuel and temperature gauge on my SLR dash (oil gauge never worked on it).
This is how it looks when you blow the regulator:
Posted Image
So I decided to rebuild the dash. Sent it away to the instrument expert (PM me if you want his details) and got the 3 gauges working again together with re-setting the odometer to zero (it had also stopped working a year or so ago). End result is tops.

Posted Image
Posted Image
Posted Image
Fitted it in today and everything works again (apart from the fuel gauge need to get the sender unit out and fixed.
I won't say how much it cost me but well worth it!
Phillip

#44 S pack

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Posted 26 November 2012 - 12:02 PM

G/day Phillip
I highly doubt the float coming off the sender unit caused your gauges to burn out. The fuel gauge would simply read empty.
Burning out the resistance wiring in the gauge usually occurs from powering up the gauges with no load on them, ie: the gauge sender wire not connected to the sender unit or a poor earth at the sender. Painting the fuel tank would be the most likely cause of a poor earth connection.
Tread carefully when you get the fuel gauge up and running as you could easily burn it out again if an earthing issue exists. I'd recommend checking the earth continuity of the sender unit to the fuel tank and the fuel tank to the body with a multimeter.

Cheers
Dave.

#45 LHSL

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Posted 28 November 2012 - 06:52 AM

G/day Phillip
I highly doubt the float coming off the sender unit caused your gauges to burn out. The fuel gauge would simply read empty.
Burning out the resistance wiring in the gauge usually occurs from powering up the gauges with no load on them, ie: the gauge sender wire not connected to the sender unit or a poor earth at the sender. Painting the fuel tank would be the most likely cause of a poor earth connection.
Tread carefully when you get the fuel gauge up and running as you could easily burn it out again if an earthing issue exists. I'd recommend checking the earth continuity of the sender unit to the fuel tank and the fuel tank to the body with a multimeter.

Cheers
Dave.

Appreciate your advice Dave. I assumed the fuel sender arm must have earthed on the bottom or top of the fuel tank hence blowing the regulator. I have currently disconnected the fuel tank sender wire hopefully this doesnt create any more dramas for me!
Phillip

#46 LJ Kermit

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Posted 25 June 2016 - 05:29 PM

hello...

 

I repaired a couple of LJ senders and some gauges for one of the forum members last year...  

 

my understanding is that the gauge sender unit is a variable resistor connected to the voltage divider in the gauge. 

 

I am not certain how shorting it to the body or tank would blow the regulator?   Crude sketch attached....more information would be nice.

 

 

my understanding is that shorting the fuel gauge sender wire to ground does not put excessive current draw on the gauge or regulator as this is what happens normally.

 

my limited experience with LJ GTR instrument panels shows that a common fault is a burnt out or heat damaged ammeter. 

this happens because the whole battery/alternator current draw is routed through the gauge and any fault condition shows up in bent needles as the gauge goes maximum up or down scale..

 

comments welcome...  more information would be great..

 

dave

 

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#47 S pack

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Posted 25 June 2016 - 07:23 PM

Dave, the magnetic instruments used in the LJ & HQ and all earlier Holdens are pretty rugged. They do not use or need a voltage regulator as used on the thermal instruments in LH/LX, UC & HJ onwards Holden. (This also includes the thermal fuel gauges introduced to 1973 &74 HQ).

 

The thermal type gauges are the ones that can be easily damaged.

The most that usually goes wrong with a magnetic type gauge is a blown/burnt/broken resistor.

One other issue is the oil dampening leaks out and wets the black gauge face around the hole for the needle shaft.

 

I've seen plenty of LJ Ammeter gauges with the plastic insulating pieces melted and the needle no longer returns to 0.

From memory I've only ever seen one ammeter with a melted needle.


Edited by S pack, 25 June 2016 - 07:26 PM.


#48 LJ Kermit

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Posted 27 June 2016 - 09:42 PM

hello...

 

 

thanks for the information.... something more for me to learn...

 

the LC/LJ type gauges are rather robust...

 

best wishes...

 

dave






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