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Atlantis Samba Member
Joined: May 07, 2009 Posts: 117 Location: Spokane, WA
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Posted: Thu May 28, 2009 12:06 pm Post subject: Oil Sending Unit, testing |
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The VW manual does not have any testing info for this so what is it suppose to read on the sending unit for the oil light?
Electrical....ripping my hair out, moving to peeling the skin soon. _________________ 1971 Transporter w/rack and ladder
1600 DP
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Thu May 28, 2009 12:15 pm Post subject: |
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I believe the OIL PRESSURE LIGHT switch is supposed to show a short below 7 psi. That is a common number in oil protection circuits. That assumes 10 psi oil pressure per 1000 rpm, so an idle of 700 RPM should give you at least 7 psi. Below that would be bad so the light would come on. Grounding the circuit at the sender should make the light on the dash come on. If you have an OIL PRESSURE GAUGE, you would need resistance numbers from the manufacture to test. Some VDO aftermarket senders come on at 9 - 10 psi so you may get an oil light flicker on a hot day at a slow idle and still be safe. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Atlantis Samba Member
Joined: May 07, 2009 Posts: 117 Location: Spokane, WA
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Posted: Thu May 28, 2009 4:05 pm Post subject: |
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Let me rephrase, what does the sender test at on a multimeter. I did ground the wire and the light came on. I want to see if the sending unit for the oil light is working correctly. What is it suppose to test at. Thanks
SGKent, still good knowledge I appreciate it. _________________ 1971 Transporter w/rack and ladder
1600 DP
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Randy in Maine Samba Member
Joined: August 03, 2003 Posts: 34890 Location: The Beach
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Posted: Thu May 28, 2009 4:12 pm Post subject: |
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With the engine off but the key in the "on" position, remove the wire to the sender. Light should go off. Touch the wire to a ground (the engine is the ground) the light should come on.
That is the test. The end. |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51003 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Thu May 28, 2009 4:14 pm Post subject: |
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Atlantis wrote: |
Let me rephrase, what does the sender test at on a multimeter. I did ground the wire and the light came on. I want to see if the sending unit for the oil light is working correctly. What is it suppose to test at. Thanks
SGKent, still good knowledge I appreciate it. |
-7 lbs= 0 ohms
+7 lbs=infinite ohms
How's that? _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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Слава Україні! |
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Atlantis Samba Member
Joined: May 07, 2009 Posts: 117 Location: Spokane, WA
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Posted: Thu May 28, 2009 6:49 pm Post subject: |
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Randy in Maine wrote: |
With the engine off but the key in the "on" position, remove the wire to the sender. Light should go off. Touch the wire to a ground (the engine is the ground) the light should come on.
That is the test. The end. |
This does not test the sending unit itself. _________________ 1971 Transporter w/rack and ladder
1600 DP
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Atlantis Samba Member
Joined: May 07, 2009 Posts: 117 Location: Spokane, WA
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Posted: Thu May 28, 2009 6:50 pm Post subject: |
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busdaddy wrote: |
Atlantis wrote: |
Let me rephrase, what does the sender test at on a multimeter. I did ground the wire and the light came on. I want to see if the sending unit for the oil light is working correctly. What is it suppose to test at. Thanks
SGKent, still good knowledge I appreciate it. |
-7 lbs= 0 ohms
+7 lbs=infinite ohms
How's that? |
what? _________________ 1971 Transporter w/rack and ladder
1600 DP
Full fill |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51003 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Thu May 28, 2009 8:14 pm Post subject: |
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Atlantis wrote: |
busdaddy wrote: |
Atlantis wrote: |
Let me rephrase, what does the sender test at on a multimeter. I did ground the wire and the light came on. I want to see if the sending unit for the oil light is working correctly. What is it suppose to test at. Thanks
SGKent, still good knowledge I appreciate it. |
-7 lbs= 0 ohms
+7 lbs=infinite ohms
How's that? |
what? |
Ummmm........ maybe you should jusy buy a new one. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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Atlantis Samba Member
Joined: May 07, 2009 Posts: 117 Location: Spokane, WA
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Posted: Thu May 28, 2009 8:54 pm Post subject: |
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busdaddy wrote: |
Atlantis wrote: |
busdaddy wrote: |
Atlantis wrote: |
Let me rephrase, what does the sender test at on a multimeter. I did ground the wire and the light came on. I want to see if the sending unit for the oil light is working correctly. What is it suppose to test at. Thanks
SGKent, still good knowledge I appreciate it. |
-7 lbs= 0 ohms
+7 lbs=infinite ohms
How's that? |
what? |
Ummmm........ maybe you should jusy buy a new one. |
I like to test things before deeming them junk. If I would have not had this mentality I would have ended up junking half of the shit on this bus that I got working. _________________ 1971 Transporter w/rack and ladder
1600 DP
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51003 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Thu May 28, 2009 10:04 pm Post subject: |
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Atlantis wrote: |
busdaddy wrote: |
Atlantis wrote: |
busdaddy wrote: |
Atlantis wrote: |
Let me rephrase, what does the sender test at on a multimeter. I did ground the wire and the light came on. I want to see if the sending unit for the oil light is working correctly. What is it suppose to test at. Thanks
SGKent, still good knowledge I appreciate it. |
-7 lbs= 0 ohms
+7 lbs=infinite ohms
How's that? |
what? |
Ummmm........ maybe you should jusy buy a new one. |
I like to test things before deeming them junk. If I would have not had this mentality I would have ended up junking half of the shit on this bus that I got working. |
Well with the engine off and less than 7 lbs of oil pressure the terminal should be grounded to the body of the sender, when the oil pressure is above 7 lbs the circuit opens, there is no in between, it's a simple switch, on or off. _________________ Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
Stop dead photo links! Post your photos to The Samba Gallery!
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Randy in Maine Samba Member
Joined: August 03, 2003 Posts: 34890 Location: The Beach
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Posted: Fri May 29, 2009 4:30 am Post subject: |
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Or perhaps hooking up a T with a mechanical gauge on one side and the OP sending unit on the other. Then you could confirm the "light on" oil pressure.
Usually they just leak oil and get replaced.
Last edited by Randy in Maine on Fri May 29, 2009 4:38 am; edited 1 time in total |
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ccpalmer Samba Member
Joined: September 17, 2006 Posts: 3850 Location: Ann Arbor, Michigan
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Posted: Fri May 29, 2009 4:35 am Post subject: |
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Atlantis wrote: |
I like to test things before deeming them junk. If I would have not had this mentality I would have ended up junking half of the shit on this bus that I got working. |
I totally support this mentality, but on the otherhand, the oil sending unit is maybe the most important thing to have working, and they're cheap...
Randy's got the trick though - Tee it with an OP gauge and see if the ohms change at 7psi... _________________ '71 Westy |
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1977_L63H_P27 Samba Member
Joined: January 17, 2006 Posts: 2345 Location: Bristol, Tennessee
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Posted: Fri May 29, 2009 5:23 am Post subject: |
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I'm interested to know why you need to test it. Is your oil warning light staying on while the engine is running? It's obviously not leaking or you'd have replaced it. If your light IS staying on, then are you sure your timing and idle are adjusted correctly? Too low an idle and it will stay on or pulsate. I just replaced mine with a Duralast unit from Autobone. It works great and was only $4. A continuity/ohm tester and some manuvering with an air compressor will allow you to test yours. From the blade connector to the threads should be a closed circuit. Then set your regulator to 10psi and pressurize the sender. Voila, open circuit!
Or spend $4 and know real quick if it's rebuild time. Peace! _________________
busdaddy wrote: |
...and try a few chubby ones until you find one you like.
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1977 Westfalia P27
you can't spell Volkswagen without SWAG
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21462 Location: Oklahoma City
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Posted: Fri May 29, 2009 6:30 am Post subject: |
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Quit screwing with ohms...and simply set your meter to "continuity"....meaning on/off...contact or not. You can thread this into a piece of pipe made of cheap tee's from homey depot and pump it up with a hand pump or bicycle pump. Keep the test rig you can use it again.
Buzzer on the VOM will be on.... with no pressure on the switch (this makes the ground contact for the idiot light)......when the buzzer on the VOM turns off as you add pressure....check gauge readings. Testing done. Ray |
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Atlantis Samba Member
Joined: May 07, 2009 Posts: 117 Location: Spokane, WA
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Posted: Fri May 29, 2009 7:08 am Post subject: |
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Ok sweet thanks to all.
I am redoing the electrical in the bus. It is a massive mess. I am almost done. The oil light and fuel gauge are the only things left to figure out.
The oil light was working and then not working, then working and now not working. I took the wire off the sending unit and grounded it to the engine and it worked. So everything from the light bulb and wiring all the way back to the sending unit works. So I wanted to test the sending unit itself.
My oil pressure is fine, the engine runs delicious. I will probably replace the oil pressure sending unit with something nicer anyway. I just want her out on the road with 100 percent perfect electrical.
I also will be installing a temp gauge and oil pressure gauge anyhow. I am soldering and heat shrinking every wire in the harness as well.
Thanks to all! _________________ 1971 Transporter w/rack and ladder
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CheapBusForSale Samba Member
Joined: May 08, 2005 Posts: 496
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Posted: Wed Dec 01, 2021 9:59 pm Post subject: Re: Oil Sending Unit, testing |
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I was told today by a gentleman who's helping me fix some wiring in my bus that to troubleshoot th sending unit, "take it out of the block and ground it hard to frame/ground/battery negative, whatever. With the key on and engine off, the light should come on (DO NOT start the engine with unit out!!!). If not, it's the sending unit. If it DOES come on, put it back in the block and turn the ignition on and see that the light turns on again. Then crank the engine and the light should go out, indicating oil pressure" _________________ Looking for Groovy Bumper Stickers? Check out my Ads!
Last edited by CheapBusForSale on Thu Dec 02, 2021 10:54 am; edited 1 time in total |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Wed Dec 01, 2021 10:04 pm Post subject: Re: Oil Sending Unit, testing |
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Light comes on when in the on position
when bus starts oil pressure builds and light should go out
If light never comes on, you can remove the wire from the sender in the on position and ground it, it should come on. If not then the circuit or light bulb, or fuse is bad.
If the light never goes out when the engine is on, the only way to easily test it is to replace it, or use a mechanical gauge to see if you have pressure.
DON"T leave the key in the on position for long so not to damage the ignition system (coil, points, electronic ignition etc) _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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telford dorr Samba Member
Joined: March 11, 2009 Posts: 3546 Location: San Diego (Encinitas)
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Posted: Thu Dec 02, 2021 10:37 pm Post subject: Re: Oil Sending Unit, testing |
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Method for fixture testing VW oil pressure sending units of all kinds:
- procure a 1-1/2" length of 1'' aluminum round stock.
- drill a pilot hole for a m10-1 metric tap all the way through the center. Use a drill press or, if you have access to one, a lathe. Tap half way through with a m10-1 tap.
- drill a pilot hole for a 1/4" pipe tap half way through the other side. Tap it half way through with a 1/4" pipe tap.
- Screw in a short 1/4"pipe nipple, followed by a 1/4" pipe "T", followed by a suitable male air hose coupling. Screw a 100 psi 1/4" pipe thread pressure gauge into the remaining "T" opening.
To use:
- screw the pressure switch / sender into the fixture m10-1 end.
- connect the fixture to a source of variable pressure shop air.
- connect an ohmmeter between the sender and the fixture.
For a switch:
- increase air pressure until the switch closes. Make a note of the pressure.
- decrease the pressure until the switch opens. Note the pressure.
For a pressure sensor:
- increase pressure and record resistance readings for pressures from zero to 80 psi, in 5 psi increments. Compare to the sensor spec, or to another sensor. _________________ '71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST) |
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mikedjames Samba Member
Joined: July 02, 2012 Posts: 2702 Location: Hamble, Hampshire, UK
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Posted: Fri Dec 03, 2021 1:41 pm Post subject: Re: Oil Sending Unit, testing |
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And even if you decide to go for a separate oil pressure transducer that feeds a pressure reading to the dash, it is a good idea to use a T piece to allow you to continue to use the original simple foolproof sender and dash light combination.
1. Because the combined senders switch the oil warning light on at a higher pressure than the stock sender.
2. Because if you rely only on a gauge to show pressure, you do not get the warning light.
(I have an electronic sender rated to 250F .. one day I got my engine really hot, I think the thermostat rod jammed, and the oil pressure dropped .
The electronic sender told me the pressure was negative, even though the warning light was only just flickering via the stock switch. In normal use with that sender, 0psi is 0.5 volts, and 100psi is 4.5 volts .. but when its hot the output goes under 0.5 volts .. ) _________________ Ancient vehicles and vessels
1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.
1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy |
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sjbartnik Samba Member
Joined: September 01, 2011 Posts: 5984 Location: Brooklyn
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Posted: Fri Dec 03, 2021 1:54 pm Post subject: Re: Oil Sending Unit, testing |
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I love telford’s answer because that’s what you need to do if you wanna test the switch - and it’s why no one bothers to test the switch. It’s a simple on/off switch. No real way to test it unless you have some method of applying a pressurized liquid into the port on the switch.
No pressure = switch closed = oil light on.
Pressure = switch open = oil light off.
Kinda the same principle as the brake light switches, just opposite. _________________ 1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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