Cortina MK1 fuel sender.

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peteleo
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Post by peteleo » Sun Sep 09, 2018 9:47 pm

A reading of 20 ohms at the fuel sender should read full on the gauge.
What does the gauge read when you touch the sender wire to ground ?
or what voltage reading do you have at the fuel gauge ?

1970 cortina GT
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Post by 1970 cortina GT » Mon Sep 10, 2018 3:22 pm

Hi Pete, so I have 3 volts at the sender, 1.8 volts at the gauge. My son is currently at school and has done a chart, you probably understand it better than me but I’m not sure from the figures what the issue is. Thanks for looking at it.Image
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peteleo
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Post by peteleo » Mon Sep 10, 2018 6:22 pm

MK1 GT '66 voltage stab. output should be a pulsating volts 5 volts
( square wave 0 volts to 5 volts )

First check the 12v input to the volt. stab. output 0-5v. Output wire connects to #1 terminal to the f/gauge. #2 terminal of the fuel gauge goes directly to the sender.

Somehow you are getting a high voltage drop at the sender ??

Your son's ohms law calculations works though.

1970 cortina GT
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Post by 1970 cortina GT » Mon Sep 10, 2018 6:48 pm

Ok I’ll check when I’m back home on the weekend, voltage stabilizer is new so I’ll check my connections. Thanks Pete I’ll let you know what I find.
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1970 cortina GT
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Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Sun Sep 16, 2018 3:31 pm

So I get 12 volts to the voltage stabilizer. I get 5 volts out of the voltage stabilizer. I have the sender out and it reads 20 full and 200 empty when I move it manually. I have hooked up my MK2 fuel gauge using the MK1 wiring harness and that reads half full when I manually move the sender arm to simulate a full tank. I know the MK2 gauge works fine. This is baffling me as it is a pretty simple circuit but I can’t figure out what to try next.
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peteleo
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Post by peteleo » Sun Sep 16, 2018 6:09 pm

Just to clarify. Your using a MK1 GT voltage stabilizer with a MK1 C5BH sender unit to a MK2 GT f/gauge. I think you may need a MK1 GT f/gauge, will solve the problem.

1970 cortina GT
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Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Sun Sep 16, 2018 6:30 pm

Hi Pete, I’m using a MK1 fuel gauge, a new MK1 voltage stabilizer and a new MK1 20 ohm full, 200 ohm empty fuel sender. I get a reading on the gauge of half tank when it’s actually full, despite a reading of 20 ohms. I get the same, half tank reading when it’s actually full when I try hooking up my MK2 fuel gauge which works fine on my MK2.
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peteleo
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Location: San Mateo,California

Post by peteleo » Sun Sep 16, 2018 7:20 pm

Sounds like you have some additional resistance in the harness or the wire is not going directly between the f/gauge and sender unit. Take a single separate wire from the f/gauge to the sender.

1970 cortina GT
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Post by 1970 cortina GT » Sun Sep 16, 2018 7:32 pm

I’ll give that a try and let you know, appreciate your advice.
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Brett Wilkie
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Post by Brett Wilkie » Sun Sep 16, 2018 8:10 pm

This may sound silly and unlikely but is it possible that the tank itself is somehow not grounded fully to the body?
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peteleo
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Post by peteleo » Sun Sep 16, 2018 8:35 pm

I believe Lee also grd'd the tank which made no difference.

1970 cortina GT
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Post by 1970 cortina GT » Sun Sep 16, 2018 9:25 pm

Yes I ran a separate ground from the tank to the battery to be certain. The sender seems to read accurately, the gauge seems to work correctly, the voltage stabilizer seems to work correctly . There really isn’t much else to it but it still isn’t giving an accurate reading . I have the sender out, the gauge out, a gauge out of my MK2 out. Jeez I’m missing something simple here. I tried the sender at the gauge with a short piece of wire and even when I simulate a full tank on the sender it still only reads half a tank on the gauge.
Life isn't complete until you have a pair of twin cams in the garage...

peteleo
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Joined: Sun Aug 24, 2008 11:57 am
Location: San Mateo,California

Post by peteleo » Sun Sep 16, 2018 10:47 pm

You haven't mentioned, that the voltage stab has to be grd'd.

It could also be the the pulsating square wave duration is not right. Staying too long on 0 volts and short on 5v. Try a used v/s.

1970 cortina GT
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Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Mon Sep 17, 2018 12:52 pm

Yes I made sure it’s grounded, in fact I added an extra ground to the whole speedo as the ground from the bulb connection didn’t seem too great. I don’t have a spare voltage stabilizer but surely the other gauges would be inacurate if it was faulty. I think I’ll try and run a wire straight from the voltage stabilizer to the gauge, just in case there’s something going on in that part of the loom.
Life isn't complete until you have a pair of twin cams in the garage...

Brett Wilkie
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Location: Vancouver British Columbia Canada

Post by Brett Wilkie » Mon Sep 17, 2018 1:13 pm

Does it make a difference if you reveres the polarity of the stabilizer? If you get totally messed up I MIGHT have a Mk1 fuel gauge and stabilizer here if I didn't discard them yet?
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