TheSamba.com :: View topic - Wiring up a "dual" VDO Oil Pressure Sender

Sun Apr 06, 2008 10:18 am

I'm installing an aftermarket dual VDO Oil Pressure sender which has two sender wires, one for the VDO pressure gauge and one which I will hook up to the Vanagon idiot light on the dash.

The two sender terminals are marked "G" and "WK". Can someone who has one of these installed tell me which terminal goes to the idiot light and which to the gauge?

(I assume "G" is for gauge...but who knows...it might be something else in German).

Warren C.

Sun Apr 06, 2008 1:19 pm

I'm no expert but I wired one of these up recently but as I remember it, the instructions for the gauge and sender indicate what goes where. I think G=gauge.

That said, most if not all Vanagon owners do NOT wire the VDO pressure sender to the Vanagon's idiot light but rather they add a "T" fitting and use an additional standard idiot sender. For some reason the dual-sender causes some hell for the idiot light. This is what I did and I'm glad for it.

So a search here (and on Google) as much has been written on this subject.

Sun Apr 06, 2008 1:39 pm

On VDO senders the terminal "WK" goes to the idiot light. In my understanding many people don't use the idiot light function on these senders relates to the pressure when the circuit closes. I think I read that the VDO sender makes the light come on at 7 PSI but the stock sender closes at closer to 4 psi. This would make the light come on more often than the stock set up. If you have a new engine this might not be an issue though.

Sun Apr 06, 2008 1:45 pm

Warren,

I used the VDO dual sender for my subie conversion. G was gauge and I did use the idiot light function for my dash light. No problems.

Regards,

Dave O

Sun Apr 06, 2008 11:09 pm

G to gauge, WK to idiot light.

I also used the same VDO kit with no problems. I mounted the clamp to the engine tin a little differently, so that it's easier to remove and install the tin:

Other than that I followed the instructions on the van-cafe web site:

http://volkscafe.com/vanagonparts.jsp?pa=ip&ip=1401786957

Mon Apr 07, 2008 4:05 am

I was one of the unfortunate (?) ones that hooked the "WK" to the idiot light. In 3 days, the oil buzzer and lamp would come on, about 10 minutes of driving.

I went and installed a "T" and included the stock sender to operate the idiot light, and now I have no problems.

A search will show a good write up done by TENCENTLIFE (who else!) and he explained the querk that some may experience when attempting to use the dual sender.

It works great for the gauge, just may cause problems with the idiot light.

Mon Apr 07, 2008 7:25 am

in my early 80 & 82 vans the Dual sender I had (scavanged from junkyard) worked in the OPPOSITE fashion as the OE idiot light sender.

Light is off when Ign on and engine off,
start engine light comes on with pressure built..

I had to use a relay to reverse the dual sender to the stock dash idiotlight..

both those vans are not 'Dynamic oilpressure sensor" systems though.

Ahh found a good explaination on the Dynamic oil pressure page

Quote:
Dynamic Oil Pressure Warning System Operation and Testing.

In the beginning oil pressure warning lights were very simple devices and earned their nickname of idiot lights. The light was powered from dashboard circuitry and grounded through the oil pressure switch. The oil pressure switch usually opened between three and five psi turning off the light. If the oil light ever came on while driving it was usually to alert you that it was too late.

The Dynamic Oil Pressure Warning System adds a considerable enhancement to the oil light warning system. There's now a high pressure switch that is normally opened, it closes at 1.8 bar. If the engine rpm is over approximately 2000 rpm while the switch is still open, the electronic control unit flashes the warning light and sounds the warning beeper. This is a far better system than the earlier system as it can warn you in advance of impending engine problems.

Dynamic Oil Pressure Warning System problems are most often just that, Dynamic Oil Pressure Warning System problems.

The diaphragms and the springs inside the switches get old and lose tension, the switch contacts can corrode from age and use.

It is very simple to test the control circuitry. With the key on and engine off the oil pressure light should be on steady on early cars, or blinking on later cars. Disconnect the yellow wire from the terminal marked "WK" ("Wahrning Kontraption" in German ) on the dual sender on the left side of the cylinder head, (this is the low pressure switch), the oil light should go out. Start the car with this wire disconnected, light should remain out. Ground this wire and light should come on and remain on as long as this wire is grounded.
Disconnect the blue/black wire from the white, high pressure switch on the oil filter flange and rev the engine over 2000 rpm. After approximately a two second delay the light and warning beeper should come on and remain on no matter what rpm the engine is running until the blue/black wire is grounded.

There are 4 oil sensors on these cars if you have both the Dynamic Oil Pressure Warning System and console gauges.

1) The smallest on the oil filter flange is a variable resistance temperature sender for the console gauge, sorry, Bentley doesn't show the wire color, it's a gauge sender, this thread is about lights and buzzers, so no more about this one now.

2) The other, bigger one on the filter flange should have a white body and a blue/black wire connected. This one is the high pressure switch. It is a normally open contact switch, it is spec'd to close at 1.8 + - 0.2 bar. If engine rpm is above approximately 2000 RPM and this switch is open, the light and buzzer should come on, the control unit has sensed less than 26 psi at 2000 RPM after an approximate 2 second delay. Once this switch has has opened while RPM's are over 2000 after the 2 second delay, the light and buzzer will continue regardless of the engine RPM until the switch closes to ground again.

3a) The combination switch/sender on the side of the head has a variable resistance sender for the console oil pressure gauge marked "G", it should have a blue/yellow wire connected. When the wire is unplugged, the pressure gauge in the console should peg, when grounded, should read zero.

3b) The combination switch/sender on the side of the head has a normally closed pressure switch spec'd to open at 0.3 + - 0.15 bar marked "WK" ("Wahrning Kontraption" in German), it should have a yellow wire connected to it. Any time this wire is connected to ground, the warning light should come on. If this wire is disconnected, there should be no light, even with key on, engine off. Any time this yellow wire connects to ground, the oil warning indicator should be indicating.

3c) Cars without an oil pressure gauge have a brown switch in the side of the cylinder head, it's function and specs are identical to "WK", above in 3b. It's part number is
056 919 081 C. This switch is a cheap easy replacement for a failed "WK" section of the dual sender described in 3c, screw it into an unused pressure port on the oil filter flange, the wire will stretch the distance and connect right up. The only drawback to this "mod" is the location for checking pressure. When located in the head, it reads pressure at the lowest possible location, re-loaced to the filter flange, the oil pressure is at it's highest possible. Note that 16V engines locate both switches in the filter flange as do ABA engines in A3s that also have lower pressure spec switches. It appears to me, by the later model lowering of the specs, the system was too sensitive as originally configured, VW lowered expectations and un-needed warranty claims by decreasing the sensitivity.

Quick, simple diagnosis of Dynamic Oil Pressure Warning System by symptom.

Assuming your engine has oil and hasn't yet started knocking, most likely causes of oil lights/buzzers are in the warning system itself.

1) 2 seconds after 2000 RPM or more, light and buzzer come on, replace the high pressure switch.

2) Oil warning light on at idle, especially when hot, replace the low pressure switch.

3) No oil light blinking with key on, engine off, replace low pressure switch and/or repair light in instrument cluster.

4) If these quick tips fail to address oil warning light/buzzer issues, do not pass go, head immediately to your nearby mechanical oil pressure gauge store and buy a gauge. Buy or make a 10 x 1.0 mm threaded adapter. Test your oil pressure, cold and hot. Know what you are looking at. Check the specs in Bentley.

--------------------------------------------------------------------------------

An oil pump pumps or flows volume, resistance to flow causes pressure. Think of a garden hose with an open end and a pressure gauge at the faucet. The longer the hose, the higher the pressure, if a very short hose is used, pressure will be very low, flow will be maximum. Squeeze the end of the hose, less water comes out but it sprays farther, flow decreased, pressure increased.
Same same inside an engine only the resistance to flow is the clearances between the bearings and the journals. Tight clearances in a fairly fresh engine makes for high oil pressure, worn clearances allow higher flow within the pump's capacity but lower pressure.
Once an engine is running, there is essentially no direct contact between the bearing surfaces and the journals, the journals ride on a pressurized film of oil. Adequate oil pressure is essential for engine longevity.

Oil pumps do fail, but it is very rare. It's real obvious when they go, driver has become instant pedestrian, engine is severely knocking or locked.
Oil pumps also wear over time, but rarely enough to cause pressure loss. If a pump shows wear, the bearings are usually worn worse.

In our engines, a low oil pressure remedy often recommended is a 2.0 oil pump. It works as a patch only. The 2.0 pump has longer gears, it can move more volume and may be able to keep up with worn bearing clearances. It is only a patch delaying the inevitable catastrophic engine destruction.

Thanks to VW's marvelous Dynamic Oil Pressure Warning System and simple loss of spring tension inside the switches, along with real flaky gauges, our cars are often mis-diagnosed as having low oil pressure. Whenever in doubt about oil pressure, check it with a known good mechanical gauge screwed directly into the engine.

Mon Apr 07, 2008 7:44 am

I'm about to do this install, and will put in the stock sender with a T, and the dual sender (since it's the one I got) and perhaps try the dual and then the stock to see what happens.

Mon Apr 07, 2008 11:56 am

The opening setpoint for the WK pin should be stamped in the body of the sender.

If it is higher than the one stamped on your OEM low switch, you may anticipate nuisance indications of the idiot light at hot idle, depending on the condition of your engine and oiling system.

The wbx OEM lo-switch opening setpoint is 0.3 bar (0.15-0.45 bar; 2.2-6.5 psi).

The excerpt Dan quoted above seems to be about VW I4 engines. The dynamic system is the same, but the hi-switch closing setpoint is much lower for a wbx. The high switch on wbx's is set to close at 0.9 bar (0.75-1.05 bar; 10.9-14.8 psi), not 1.8. A 1.8 switch might also cause nuisance warnings of the dynamic system with most wbx's, even ones in good condition.

I see that in Bentley, the wiring diagrams for '88 and later wbx vans show a hi-switch with the 1.8 bar setting. I believe this to be in error.

Mon Apr 07, 2008 1:18 pm

dobryan wrote: Warren,

I used the VDO dual sender for my subie conversion. G was gauge and I did use the idiot light function for my dash light. No problems.

Regards,

Dave O

Dave,

I'm also using the dual sender on a Suby engine. Is your van a latemodel version with the dynamic oil pressure circuitry. If so, I assume you used the low pressure sender wire hooked to the VDO WK terminal.

Right?

Warren C.

Thu Jul 10, 2008 7:21 am

What is the source of the magical T-connector splitter thingy? I'm putting in a 2.1L WBX with an existing pressure gauge sender line set up, but I want to use the factory .3 bar switch to trigger the oil light without having to rely on the dual-pole sender.

Thu Jul 10, 2008 9:07 am

A magical hardware store.

Use an enchanted 1/8" FPT brass tee.

Thu Jul 10, 2008 10:31 am

I will encant +30 magic upon your install. It will ensure sucess, :)

Thu Jul 10, 2008 3:34 pm

tencentlife wrote: A magical hardware store.

Use an enchanted 1/8" FPT brass tee.

Isn't the oil sender a 10mm hole with different pitch threading? 10x1? That couldn't be good.

Thu Jul 10, 2008 7:44 pm

It's a near perfect match. The sender threads wlll bottom in the FPT taper and seal themselves.

Fri Jul 11, 2008 5:24 am

tencentlife wrote: It's a near perfect match. The sender threads wlll bottom in the FPT taper and seal themselves.

Wow! Magical indeed! :D

Sun Nov 15, 2009 2:17 pm

I'm putting a suby engine into a bug and was wondering if anyone knew if VDO makes a dual sender for the Subaru EJ20? I have a dual sender from my VW engine and I could use an adapter but wondered if I could do it with no adapter. Or at the very least what thread sizes would I need for an adapter.
thanks.

Sun Nov 15, 2009 3:45 pm

Hi

I have the VDO oil sending unit on a "sandwich" adapter on the oil filter totally independent of everything else on the van. I have added a warning light wired from the VDO sending unit. I left the "original" considering I have a Sub engine, totally alone and untouched.

You can see the additional oil pressure warning light on the very left of my auxiliary dash.

No, problems, no complications, no nothing. straight and simple

Good luck :lol:

Sun Nov 15, 2009 10:56 pm

Thanks for the idea although I am using a sandwich adapter for an oil cooler. It's not the same one that has the oil sender fitting. I'll have to double check to see if it does have a fitting for the sending unit.

Sat Jul 06, 2013 2:00 pm

Hey VW guys, I need help. I have a 73 Beetle, and I put a 2 pole VDO Sender on the block, and wired it to VDO gauge. I have the G wire going to the S terminal on the gauge and the WK wire going to my idiot light on the speedo head. The + terminal is on a 12v switched terminal on the fuse block. When I turn the ignition on, the gauge pegs all the way over and does not come back when the egine cranks up. I do not care about the idiot light, I just need my gauge to read oil pressure. Can somebody help me? Thanks, Barry