Dash Oil Pressure Light ?

[rcf925]

I am trying to troubleshoot why my oil pressure light is not comming on when I turn the key on, I have 12v to the sending unit with key on along with alternator light and all other instrument cluster lights work. I've check bulb, Cleaned the contack where bulb socket goes on cluster. If I take the oil light socket out with bulb still in it and touch the outside of socket to ground the light works with key on. so if all the other lights in cluster are working I don't think it's a grounding problem, I also replaced sending unit, Still no light. I'm not bad with electrics but someone here is probably much better, It's a 63 ragtop converted to twelve volt and light has been working

[hitest]

I hope Glutamodo will explain this better than me, but here's my go of it...

I'm not sure how you tested just the bulb housing by pulling it out and touching it to ground. Because if the wiring is correct the positive is shared among all three bulbs in the small, removable cluster on the speedo's underside. Therefore, you had no positive with which to ground. It should light only if you involved another source of power- or if you bypassed (unplugged) the power lead for the cluster just to test the circuit on the oil bulb.

Normally, the oil sender grounds and illuminates the bulb until oil pressure increases- thus opening the circuit and the light goes out. My guess is your test somehow simply resulted in another closed circuit- and lit the bulb, but the sending unit may not be working as it should.

Again, I sure hope the reliable pros visit this thread soon for you.
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[bluebus86]

sounds like the pressure switch is not working. when the key in on, but engine not running, the oil pressure is zero and thus the switch should ground out to the engine case, which serves to ground the light. when ever the key is on, the bulb should havenpositive 12 or 6 volts to it. it is the pressure switch at engine which supplies ground (negative) to the bulb when pressure is too low. when oil pressure gets high enough, the pressure switch opens, which cuts off the ground to the bulb.

To test if it is indeed a bad pressure switch verses a broken wire or other fault, turn on the key switch, then remove the wire off the presure switch and touch the wire to ground (engine case) this should illuminate the bulb, if it does illuminate, suspect a bad pressure switch. also note that if lots of teflon pipe tape was used to seal the pressure switch threads, that the tape may prevent the switch from suppling ground even when the pressure switch is closed. Teflon pipe tape for this reason is not the best choice for the threads. if no teflon tape, then replace the switchif you find grounding the wire at the switch does indeed illuminate the bulb.


so the light is grounded by the pressure switch when pressure is too low, the light should always have 12 or 6 volts on it when ignition is on.


good luck
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Help Prevent VW Engine Fires, see this link.....Engine safety wire information

Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022

[rcf925]

So after testing some more I think I have a short cause the wire to the sending unit is showing 12v when the key is turned on, That is just supposed to be a ground right? I also put a new pressure switch in to be safe even though I think my old one is still good.

[KTPhil]

[bluebus86]

[sjbartnik]

[rcf925]

Quote "please take that wire, with ignition on, and ground it to the engine case, that should light the bulb, if it does light the bulb, that indicates that the pressure switch was failing to ground that wire at low pressure. symptoms still point to a problem with the pressure switch or its ground contact to the motor. had there been no 12 volts on that wire with ignition on, then you would conclude the problem is not the pressure switch, but rather the problem would be no positive 12 to the other side of the bulb, or a break in that wire. "

So I performed the test with key on and touched sensor wire to engine case, I get a spark wire gets hot immediatly and dims alternator light like a short somewhere, I also have added a new trans to motor ground strap. Previous owner re wired car with new fuse box with blade fuses which is fine, I'm going to start pulling fuses to see where power is comming from to oil pressure switch and start looking for short or any thing else wrong

[bluebus86]

[KTPhil]

Any chance someone swapped the oil and gen lights or wires at either end?

[sjbartnik]

[Cusser]

I wonder if that wire, or the wire to the coil positive terminal, is a secondary wire that someone in the past hooked up. It's obviously not fused as it sparked and got hot when touched to ground.

So it's definitely NOT the wire for the pressure sender, unless someone screwed up the wiring up front in the trunk.
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[rcf925]

[mukluk]

Your wiring and fuel line are making my eye twitch...

Anywho, it appears the wire coming off the oil light in the speedo is green, so what does the loose green wire in your engine pic go to?
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1960 Ragtop w/Semaphores "Inga"

[rcf925]

[bluebus86]

oh my, thats not a stock set up for sure. I think time would be well spent tracing wires and making up your own diagram that shows what you have you may have to remove wires connections one at a time and test for continuity to figure out what is routed where, there is even a splice I see with a color change.

the fuel filter and long hoses are rinky dinky and might be very hazardous. the filter should not be in the engine bay get it under the car near the tranny away from ignition sources. engine tin is missing around the heatrisers, no seal around the engine bay tin (or if it is there it is installed wrong. that aftermarket fan house is likely one of the poor quality ones with impropper internal directional vanes, the bumper on the aircleaner appears to be for rubbing on the decklid you dont want thedeck lid hitting that aircleaner, what kind of carb is that?
you dont have any crankcase breather system lacking that may cause the engine to leak oil.

please carry a very large fire extingusher.

the overall profile photo shows a very nice looking bug, but the trunk and engine area are scary, but fixable with a bit of effort.

anyway get a pen and paper and draw up a wire diagram to reflect what you have, this will come in handy many times in sorting this out. if wire colors are confussing, you can purchase wire number tags at electronics stores so the ends can be labeled.

anyway for your original problem, trace which wire is which, evidently the wire you thought goes to the pressure switch probably aint.

good luck
_________________
Help Prevent VW Engine Fires, see this link.....Engine safety wire information

Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022

[rcf925]

[KTPhil]

Nice looking car. Too bad the PO hacked the wiring. It is not all that uncommon, but it's a real PITA for the next owner (you).
One option is to buy a new wiring harness and set it all back to stock, rather than piecemeal the individual wires. Another layer of pain, but then it's done and easy to troubleshoot later.
In the meantime, adding labels (using the terminal numbers form the device and/or wiring diagram) at every connection will help with setting it right. Those dymo labelmakers (the white tape style, not the embossed style) works well for this.

[bluebus86]

[KTPhil]