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Discussion Starter #1
Tired of the fuel level light coming on at half a tank. New sender already installed and same behavior, starts warning me I'm low on fuel at half a tank. :rolleyes: So, looking through the repair manual, I see that the fuel tank sender uses ground G186 in the right hand side of the trunk. I removed the carpet and went looking for it. Turns out to be a major ground point. G186 is: Motronic ML4.1 Ignition/Injection, Side markers, turn signals, misc dome lamps, instrument fuel transmitter, Door open warning lamps, rear defog, trunk opening, fuel lid popper, Alarm, Radio/telephone, and suspension in the S. Of course all these system work in my car except the fuel light, so not likely a problem there, but I went in and cleaned and tightened the ground point anyway. Of course the light is still on. Anyway, thought I would photograph this ground point and point out how important this one is. I think I will look next at the cluster connection. It is a PPL-BLK wire B3 (third one from right in the upper right hand connector at the cluster and check the cluster grounds too.
Charles
 

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Now I know why fuel gauge and low level fuel light were not working when I started up Sara's wrecked B yesterday. I had unhooked all those ground wires at G186 when I sawed off twisted sheet metal.
 

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Discussion Starter #3
Dug into this little problem a bit further today. Removed the cluster and disassembled it. Found no corroded contacts at any of the four connectors. Inspected the circuit board and found no cracked solder joints. I had to deal with the coating on the inside of the cluster. It is yet another area where a coating turns to goo. I took the goo off with lacquer thinner and then sanded the black plastic with 400 grit sandpaper wet. It looks good and decided I didn't need to paint it flat black. All back together and it looks good. Still though the level light glows.
This evening I went back to the manual and decided to find G170 connector (not a ground even though it's identified with a G). PPL-BLK and PPL wires from the sender in the tank are in this connector. This is a major connector for lots of items that go from under the dash to the right rear of the car. Found it under the dash panel on the pass. side, one screw and the panel drops down. The connector is attached to the panel. Very easy to get to. I separated it and plugged it back together. Pull the ridged square to open it up, put it back together and push back down on the ridged square at the top of the connector. Turned the car on and now no light! Let's see if it fixes the issue for anybody else that has this problem. ;) It will take about 2 minutes to try it.
Charles
 

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Ditto, everything the same as with my experience except I was trying to trace randomly-popping boot release and cycling climate control panel power. I seemed to get a result from cleaning G-170 with the slide-out clasp - it's in driver's footwell for RHD.

I haven't yet had a problem with fuel-low light. I am, meanwhile, now having over-temp red light problems all over again with a different 164 that previously never had red-light problems. Sigh.

I also smudged the degraded coating inside instrument cluster (took it apart to add ground wire), like you I wet-sanded but with hot soapy water which seemed to shift the goo just as well, and then I repainted with matt black spraycan, just to be assured of an even, dark colour.

Cheers,
-Alex
 

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Discussion Starter #5
Scrutinizing the manual again. It says that the light illuminates with the closing of the contact in the sender, so that means the sender is doing just that (somehow :rolleyes:). So that also means grounds and the cluster, etc are all working correctly. Only, it's not working correctly. I'm tempted to go to G170 and just disconnect the PPL-BLK and be rid of the light. It flickered again at a good bit over half a tank with a new sender! How can the sender be closing the circuit for the light when it's that full???? What else could be closing the circuit? You know what, anywhere the PPL-BLK wire could be touching ground it would cause the light to come on, but it doesn't do this when Full, Full, so it can't be that either. As Alfisto Steve says, I think it might be the Ethanol! But what could the Ethanol be doing to cause this? How could Ethanol complete a ground circuit? :confused:
Charles
 

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As Alfisto Steve says, I think it might be the Ethanol! But what could the Ethanol be doing to cause this? How could Ethanol complete a ground circuit?
I go along with that - because I've never had that problem or known of a 164 with that problem in NZ (where we don't have ethanol in fuel) - and I reckon I've seen just about every electrical problem there is ;)

It sounds like the sender is having a mechanical problem - perhaps there is a material disintegration causing the contacts to close too early?

EDIT: sorry, just re-read your first post and realised that you've already fitted a new sender. It's certainly a puzzle. Do you think that signal for the light is processed by electronics? I know on my 164 when I slow to a stop, the light comes on (if the tank is 1/4 full) and it seems to take a surprising while for the light to go off again.

In my 156, once the light comes on, it never goes off - electronics 'latch' the signal. Actually in the 156 there are no contacts for the light; it is switched on when the level reading hits a certain point. I guess, if the puzzle becomes really unsolvable, it would be possible to rig something similar for the 164 (operate the light off the fuel level reading via electronics).

-Alex
 

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Discussion Starter #7
Looking at a Wikipedia (if you can believe anything there) entry about Ethanol, it says that E85 is conductive and gasoline is not. It says that fuel pumps in flex fuel vehicles must have fuel pumps that can operate in conductive E85. We aren't running E-85 of course, but if this thing is sensitive enough, our 10% Ethanol mix might be enough to complete the light circuit here? I try to buy gas from a station that claims no Ethanol but I don't always fill up there. Opening up my old sender, I can't make heads or tails about how conductive fuel would make this thing close the low fuel light switch, but I think that's what is happening here, or did I just get a bad new sender? :rolleyes:
Charles
 

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Some time ago, I had my car off the road for quite a while to restore it after a deer strike.

When I went to re-start it, there was a problem, which in the end I fixed by removing the tank and cleaning it. The fuel pump rubber mount had turned to goo, and was all over the inside of the tank, pump etc. I fitted a new pump, strainer, mount and filter.

I could see a ring of goo inside the fuel level sender too. After a bit of fiddling, I found it could be taken apart by taking the top off...my memory tells me it's sort of a bayonet fitting, push down and turn - I think!

Anyway, I cleaned the goo out, and reassembled the sender. I learned that there are two holes in the body of the sender to allow you to hold out the sliding arms that give you the readings - one for fuel level, and one for reserve level. So far so good. After all was back together, I had a reading on the guage, but the reserve light comes on at just under half a tank.

Thinking back, I remember that the top of the sender can be replaced in two positions, 180 degrees apart. I'm fairly sure I got the wrong way round.

Since then, I haven't been back in the tank, and I've learned to live with the early reserve light. I think there's more goo in the sender now, because it seems to "hang up" in one spot for a while, and then drop hard to a new lower level.

Next time I'm working back there, I'll pull the sender and see if my theory is right.

Steve, with the back off your daughter's car, you might be able to quickly check to see if what I remember is right eh?

I'll post what I find. Dennis.
 

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Discussion Starter #10 (Edited)
Dennis, The top is held on by two tabs. The float can only go back into the tube one way (because the contacts are offset to one side of the float top), so if you pushed the two contacts in through the holes in the sides of the top cap as you put the top back on, than it's put back together right. It is hard to get it all back together though, because you have to get the springs all back in at the top and bottom of the float, just right. I'm suspecting it hangs up because one of the springs is not in there right. I could remove the cluster and then the bulb, but simply disconnecting the PPL-BLK wire from G170 will be much faster and easier than all that.
Charles
 

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Thanks Chaz, Sounds like you've been in there too, and remember it better than I do.

I think I still need to pull it and see what I can find......someday soon.
 

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Tired of the fuel level light coming on at half a tank. New sender already installed and same behavior, starts warning me I'm low on fuel at half a tank. :rolleyes: So, looking through the repair manual, I see that the fuel tank sender uses ground G186 in the right hand side of the trunk. I removed the carpet and went looking for it. Turns out to be a major ground point. G186 is: Motronic ML4.1 Ignition/Injection, Side markers, turn signals, misc dome lamps, instrument fuel transmitter, Door open warning lamps, rear defog, trunk opening, fuel lid popper, Alarm, Radio/telephone, and suspension in the S. Of course all these system work in my car except the fuel light, so not likely a problem there, but I went in and cleaned and tightened the ground point anyway. Of course the light is still on. Anyway, thought I would photograph this ground point and point out how important this one is. I think I will look next at the cluster connection. It is a PPL-BLK wire B3 (third one from right in the upper right hand connector at the cluster and check the cluster grounds too.
Charles
I have the same problem. New sender and the light comes 3/4 of tank full.
I suspect either bad sender or it is positioned wrong. I thought I have it going in the right way but may have put it in another way if it even matters. Most senders do need to be put in the tank a certain way. But it bugs me to death and may put the old one back in which was working fine. I put the new one in when I pulled my tank and re-did it all.
So I will be curious to see what comes of this and now that you are on it I may hit this next week too to see whats up! Have not touched this since I put the new tank in.

Jason
 

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Discussion Starter #13
I was careful to orient it exactly as the old one when I put it in so I don't? It seems to not give me as much of a problem since disconnecting and then reconnecting G170, but that isn't really making any sense to me.
Charles
 

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I agree with Charles that the whole sender unit only re-assembles one way in all respects.

I did the sender rebuild about two years ago but I remember that part clearly as well as the fact that the amber light shone just as brightly as beforehand.
I tried disconnect/connect G170 trick and at first I was ecstatic last Monday morning as both my amber low fuel warning light as well as the adjacent red temperature sensor light were out for the journey in to work.....well almost.
The red light came back on steady during the last mile and the amber light was flickering very occasionally.
Since then the red light is back to its permanent ON status as we all know from the replacement sender units at the thermostat housing.
The amber light is far less ON but comes ON and OFF regularly.
The G170 trick did improve something but it did not resolve the problem altogether.

Something else lurks.....I am hoping Charles maintains momentum in this regard.

I have just removed another sender unit from a rebuild project in progress and I will re-visit the whole assembly process soon.

Ta,

Neville.
 

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Discussion Starter #15
Well my Volvo 240 doesn't have an "idiot light" and I have yet to run it out of fuel, and I figure the cause really is Ethanol with this light, so I went back in to G170 and cut the purple-black wire and now no more amber light driving me crazy all the time. I'm pretty happy about it actually, even if it is kind of a "hack" repair. I did all I could looking for the fault and was left empty handed basically. :rolleyes:
Charles
 
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