Brake fluid, achtung! and low oil pressure lights on
07-09-2015, 01:27 PM
#1
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Brake fluid, achtung! and low oil pressure lights on
OK - I did a search already and did not find anything that answered either of my issues. Also Clark's Garage does not have anything related to these two issues.
Car is a 1986 N/A. Instrument cluster is from an 85.5 to get functional odo gears. The same warning lights were on when the original cluster was installed.
1) The brake fluid warning light is on. The reservoir is full and I also swapped the level measuring/cap unit from another car. What am I missing? I hadn't considered jumping the two connectors together until now. Is that how the circuit works when "full"? Any other ideas?
2) The oil pressure was reading beyond 5 bar and the light was one. I suspected a bad sender. See the photo. This was taken before the sender was replaced. Now with a new sender the reading is at about 4.5 bar at start up. A far more believable value. However - the warning light is still on. There is plenty of oil and there is good pressure (no lifter clatter and a short 5-mile trip have effectively confirmed this). Is there a pressure switch (beyond the sender unit) or another reason the warning light would be on when there is sufficient pressure?
Once these are resolved, I expect the achtung! light to go out as well.
Car is a 1986 N/A. Instrument cluster is from an 85.5 to get functional odo gears. The same warning lights were on when the original cluster was installed.
1) The brake fluid warning light is on. The reservoir is full and I also swapped the level measuring/cap unit from another car. What am I missing? I hadn't considered jumping the two connectors together until now. Is that how the circuit works when "full"? Any other ideas?
2) The oil pressure was reading beyond 5 bar and the light was one. I suspected a bad sender. See the photo. This was taken before the sender was replaced. Now with a new sender the reading is at about 4.5 bar at start up. A far more believable value. However - the warning light is still on. There is plenty of oil and there is good pressure (no lifter clatter and a short 5-mile trip have effectively confirmed this). Is there a pressure switch (beyond the sender unit) or another reason the warning light would be on when there is sufficient pressure?
Once these are resolved, I expect the achtung! light to go out as well.
07-09-2015, 02:21 PM
#2
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I came across a clue in another thread for a similar issue. See the highlighted items in the wiring diagram. The warning lights terminate at something in the cluster. The same items are captured in the attached photo (from the other thread). Note that these have been highlighted and labeled. Of particular interest are 10, 11 and 12. What are these things? If this is the root cause - what may have happened? I've not dissected this part of a cluster before.
07-10-2015, 02:12 AM
#3
Check the female plug at the reservoir...I have had issues with the wire corroding but not the sheathing...from brake fluid I assume.
The sender is two units in one. Disconnect the wire for the light, if it stays lit, the short is in that wire. If it goes out, see if that terminal is a short to ground while you have the minimum pressure. If so, that would be a half bad sender (Maybe black/red from your pix)
the other wire is for the gauge.
Did the wires get jostled during the cam cover install? Same car? If both clusters do the same thing, I don't think it is the cluster.
The sender is two units in one. Disconnect the wire for the light, if it stays lit, the short is in that wire. If it goes out, see if that terminal is a short to ground while you have the minimum pressure. If so, that would be a half bad sender (Maybe black/red from your pix)
the other wire is for the gauge.
Did the wires get jostled during the cam cover install? Same car? If both clusters do the same thing, I don't think it is the cluster.
07-10-2015, 08:21 AM
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Check the female plug at the reservoir...I have had issues with the wire corroding but not the sheathing...from brake fluid I assume.
The sender is two units in one. Disconnect the wire for the light, if it stays lit, the short is in that wire. If it goes out, see if that terminal is a short to ground while you have the minimum pressure. If so, that would be a half bad sender (Maybe black/red from your pix)
the other wire is for the gauge.
Did the wires get jostled during the cam cover install? Same car? If both clusters do the same thing, I don't think it is the cluster.
The sender is two units in one. Disconnect the wire for the light, if it stays lit, the short is in that wire. If it goes out, see if that terminal is a short to ground while you have the minimum pressure. If so, that would be a half bad sender (Maybe black/red from your pix)
the other wire is for the gauge.
Did the wires get jostled during the cam cover install? Same car? If both clusters do the same thing, I don't think it is the cluster.
Ok - that makes sense. I'll have a good look at the wiring diagram and get a better idea what is what there.
I totally agree that it's not in the cluster - but it has me wondering if my recollection is correct. I might need to swap the clusters again to confirm. Memory is always the second thing to go.
Different car. This is one I picked up late last year. It had been unmaintained for a few years. I wanted to be sure it got new belts, waterpump and oil before doing anything else. Now I am working out the smaller details. Along with these electrical inconveniences, it needs engine mounts (surprise) and I can't get the hatch to open.
Other than that - it looks to be a solid car that should be a good DD once the little details are worked out.
Maybe I'll start a new thread covering the work...
Last edited by Scott at Team Harco; 07-10-2015 at 12:53 PM.
07-10-2015, 10:54 AM
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corrosion on the plug connectors? wiggle test on wires good? is there an ink crack on the mylar sheet in the cluster? Had this on a Nissan once..drove me bonkers until I went over the sheet with my optivisor and 10+ magnification..to find the break in the circuit...good luck...
07-14-2015, 09:10 AM
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corrosion on the plug connectors? wiggle test on wires good? is there an ink crack on the mylar sheet in the cluster? Had this on a Nissan once..drove me bonkers until I went over the sheet with my optivisor and 10+ magnification..to find the break in the circuit...good luck...
I did a resistance check on the two wires at the master cylinder. Both are equal to ground. How would this happen?
Further more, I swapped back the original cluster and found that the brake pad wear light is also on. I didn't notice this in the other cluster because I removed that bulb.
Too bad removing the other two bulbs won't extinguish the achtung light. 
This eliminates the cluster as being the source of the problem. Is there anything else common to these three areas to provide the false warning? I'm not seeing it in the wiring diagram.