1990 T3 Oil light on solid - [SOLVED]

[jmac66]

Hi there, hoping to get some help and thoughts on this one!

The oil light on my T3 has started coming on solid. It's dim at idle but goes bright when rev'd.

My current hypothesis is it's a false reading because to my understanding it should only ever flash/buzz but never come on solid? It also doesn't make sense to me that the oil pressure would reduce with revs.

What I've tried:
- To test the buzzer/flasher, I disconnected the sensor in the engine bay and rev'd it to 2k but it does the same thing regardless of whether the sensors are plugged in or not
- Tested the two sensor leads with a test-light following Thomas EXOVCDS video which came back correct - indicating the sensors are ok
- Cleaned a ground crown
- Removed the oil pressure logic board to check for damage - not sure what I'm looking for but it has got a brown residue on it, unsure what it is however - see photo.

What I haven't tried yet:
- Oil pressure test (will do one but I think its unlikely as the engine was rebuilt not long ago)
- Replacing the sensors


Questions:
- Keen on any ideas / help!
- Am I right that the later model T3s with the buzzer/flasher oil pressure units shouldn't ever come on solid?


Video of the light coming on during a cold start:

Link


Photos of oil pressure logic board:

[ZsZ]

here is a quick description on the system:

https://brickwerks.co.uk/blog/vw-t3-oil-pressure-switches/

Check the pressure with a gauge to be sure.

IIRC the solid/blinking is year related. 87-88 and newer is blinking.
_________________
Zoltan
1.9 MTdi 2wd Multivan (ex Caravelle)
Van since 2006, engine since 2008

[MarkWard]

I’ve found the wire from the oil pressure switch, the one between the pushrods melted to the engine case where it is routed up to the engine compartment on quite a few vans. This could cause your symptom, but yes always verify the actual pressure.

[jlrftype7]

[dabaron]

shorted wire, bad sensor (they aren't good quality these days), spun bearing. it's probably either of the first two, fingers crossed.
_________________
1991 Vanagon GL Camper
i had no idea i wanted to be a mechanic

[djkeev]

I'd atop running that engine at all
UNTIL
You screw in a real pressure gauge and see whether or not you have oil pressure and what pressure the gauge reads.

Don't just assume you have oil pressure, verify that you have oil pressure.
_________________
Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[jmac66]

Ok so update - I've replaced the two sensors which were relatively crusty, and unfortunately its still doing the same thing.

Next step I'm taking is to verify oil pressure once I've borrowed a tester from a mate.

Haven't been running it other than to check if any of my attempts have been successful.

I still think its highly unlikely its low on oil pressure as it doesn't make sense the light is solid - but keen to verify for peace of mind.

Thanks for all the help so far!

[jmac66]

Ok good news - I think pressure is ok.

Making 4.5 bar on start / cold idle which is healthy according to these specs:
https://club8090.co.uk/wiki/Petrol_engines_Oil_pressure_survey

But still leaves me with my false reading - and I don't intend on just running it disconnected.

Any new ideas?

[zerotofifty]

[dhaavers]

What do you know about the engine in your ‘90? The stock 2.1 petrol
with your symptoms are a known trouble problem, but a rebuild with
better rod bolts can be much more stout.

Cold OP is a great way to verify oil viscosity, but NOT an indicator
of engine health. HOT OP is what you need to know. Run on the
highway for 15-20 minutes <or> until radiator fan has run a time
or two, then look at your OP readings. That’ll tell the story.

You still haven’t verified wiring from your new OP senders to your
dash cluster…more homework for you!

- Dave
_________________
86 White Wolfsburg Westy Weekender
"The WonderVan"
<EDITED TO PROTECT INNOCENT PIXELS>

[Ahwahnee]

I'm not much interested in most of the gauges that can be added but an oil pressure gauge seems like a must-have item when driving an old vehicle with a high mileage engine.

[jmac66]

Thanks for the replies.

I know to truly validate pressure that I'd need to test more comprehensively but I really never thought it was oil pressure in the first place - the engine was rebuilt not long ago and is otherwise healthy.

The dash light is also not behaving in the way that its supposed to even if it were to indicate low-pressure running.

At this point, I think its catching power from somewhere as it lights brighter with revs, and flashes in sync with the blinker if it is on too.

Appreciate the input so far!

[ProvoCyclist]

I’m gonna ask two painfully obvious/ultra basic questions first and then a couple that are slightly out in left field, if you don’t mind
1) is your oil level correct?
2) what weight is it?
Now that’s out of the way, you say the engine was recently rebuilt.
3) Was the oil pump replaced as part of the rebuild?
4) What’s your hot oil pressure?
I ask this because I had installed a rebuilt WBX in my first van (mind you, this was 15+ yrs ago). Initially everything was superb. After a couple thousand miles the hot oil pressure was terrible regardless of rpm. It turns out the driven gear in the oil pump would expand just enough to the let the shaft get loose. When it was cold, everything looked great. When I pulled the pump out to replace it, I was able to separate the two pieces without much doing.
_________________
Clark
Current: 1986 Tintop GL 2wd, stock 2.1L, manual trans, Savanna Beige Metallic LH1V.
Past: 1985 Sunroof GL, 2wd, Subaru 3.3L, manual trans, resprayed to Diamond Silver L97A

[jmac66]

Ended up being a faulty voltage regulator.

Had a battery overcharge and toast itself - voltage regular resolved that issue along with some other electrical gremlins like the oil dash light behaviour.

Thank you all for the replies!

[vanis13]

[jmac66]

Guessed a bad voltage regulator for the battery - had all the symptoms of an overcharge. Swapped a spare in and tested it against the voltmeter and it was accurate.

Haven't officially tested if the last one was the cause but I'm comfortable with my assumptions. It was also visibly a bit mangled.


Edited the post to solved - thanks!

[vanis13]