1992 RRC.

The oil light blinks for about 10 seconds on every startup. He who would help the expert-to-be must answer me these questions three:

-I assume that the logic unit has a lower boundary for oil pressure. Does it have an upper pressure boundary where it trips the lamp also? (The truck is overfilled by about 1/2 quart which is why I ask. If left alone, it will leak/burn down of its own accord)

-Does anyone know the size fitting that will screw in to the oil switch hole to adapt a pressure gauge? Is it some kind of NPT?

-I changed the oil about two weeks ago and forgot to fill the new filter. If it had an airlock as described in the manual, the motor would have blown up by now, right? Trying to eliminate a 'partial air lock' or 'intermittent air lock' as a possibility.

Your new oil filter may have a bad anti drain back valve. Drain back overnight can sphion a fair amount of oil out of the valve train.

The blinking oil light is for low level of oil. The light is steady red with low pressure. Sometimes the oil level light will be in error due to broken wires at the oil level sensor that is screwed into the side of the pan. The low pressure switch portion of the circuit is near the oil filter.

Check you oil level. If you are using the large filter and and didn't fill it, just adding the usual amount of oil will leave you 1/2 to 3/4 of a quart low.

On my 1991 the light will go on just as the oil level starts to drop below fill on the dipstick.

This is a common problem. My 1990 does it all the time. Oil level if fine. I have "heard" from the LR mechanics that the sensor is suspect. I don't really feel like fixing it so I have learned to live with it.

I didn't even check my oil level when it started blinking.
Last friday i checked and had to fill three litres (quarts) :rolleyes:

T

Just disconnect the logic unit. It will still work for the pressure sensor I believe.

JP

if you're really annoyed with that, turn the ignition on/off/on again, and it won't stay blinking.

Disconnecting the logic unit disables the low pressure functionality.

This is a very common fault, the logic units fail and begin to do this. At one point, I did a write-up on how to retain pressure functionality without having the annoying flashing light, but lost the write-up and the time required to open up the dash to reverse engineer it is too much, on the rare occasion that the vehicle is in the shop.

To determine if it is the sensor, disconnect the sensor and check functionality with it open circuit and jumpered. If no difference with either condition, it's the logic unit. The logic unit is under the steering wheel, up quite high, on the left side IIRC (NAS). There's a bunch of stuff up there, make sure you have the right black box!

IIRC, I ran a new wire from the pressure switch to one of the wires from the logic unit, bypassing the logic unit. The method by which the instrument panel operates is somewhat confusing (British?) and it took me awhile to figure it out, but if you duplicate my efforts, please post up so I can fix Shopgrrl's truck :grinpimp:.

Believe it or not, the local dealer told my client they merely disconnect the unit and don't worry about low oil pressure warnings. I guess if you're in the business to replace blowed up engines due to your own stupidity, you can do things that way.

The threaded fittings are BPP, British Parallel Pipe. If you have a well-stocked hydraulic shop local to you, you may be able to find the necessary fittings, otherwise, I take the pressure switch and tap it for 1/8" NPT and use this as an adapter. Some of the on-line hot rod shops have adapter fittings as well, but you may have to search for them.

PT

Thanks. As always, I'm humbled.

i am with pendy on this one you can unplug the logic unit and still have the oil pressure sensor turn on the light

i am with pendy on this one you can unplug the logic unit and still have the oil pressure sensor turn on the light

Both sensors go to the logic unit.

the oil sensor grounds before it gets to the logic unit

the oil sensor grounds before it gets to the logic unit

OK, after looking at the wiring diagram, now I'm really confused. It appears as though the pressure switch is independent of the logic unit and the logic unit grounds the circuit to illuminate the light.

It appears as though if one were to remove the logic unit, the pressure switch should continue to operate.

I stand corrected (again).

OK, after looking at the wiring diagram, now I'm really confused. It appears as though the pressure switch is independent of the logic unit and the logic unit grounds the circuit to illuminate the light.

It appears as though if one were to remove the logic unit, the pressure switch should continue to operate.

I stand corrected (again).
I'll bet you a brand new oil pressure sender that I can throw a logic unit farther than you (prolly can't throw you far at all) but I've had some practice with the illogical units.

Matt Browne
Overland Engineering

I stand corrected (again).

Some days shine brighter.

Some days shine brighter.

I know you would have preferred it if I'd said that I stand in awe of your voluminous knowledge of such!:flipoff2: