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hey guys, two things,

1/ forgive me if this has been covered before, i searched through tons of threads but could only find info about oil pressure gauge and/or oil pressure warning (red) light.

the check oil (level) light in my car is constantly on, this is the red light with a picture of a dipstick in a circle. where is the sensor for this? i believe it is seperate to the sender units in middle of V (gauge), or under dizzy (pressure warning) ?

2/ the dash "backlight" that illuminates the oil pressure gauge is dim making it difficult to read the gauge itself.. i'm sure i've read details on dash disassembly to replace faulty bulb (likely cause?), but couldn't find it when i searched.. anyone point me in the right direction?

cheers
 

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The low oil sensor is located near the base of the dipstick tube. Check the connectors to see if it is covered over in crud, shorting out between the two terminals.
 

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The theory of operation for the oil level sensor is:

- Thin resistance wire is wrapped around bimetal strip with contacts in series with resistance wire. One connection terminal is connected to resistance wire, the other to stationary contact.

- At ignition switch-on, approx. five volts flows from the check control unit, through resistance wire, through closed contacts, and back to the check control unit.

- If oil level normal, nothing happens - heat dissipates into surrounding oil - contacts remain closed. Check control unit shuts off current after about five seconds.

- If oil level low, heat builds up in bimetal strip and contacts spring open. Check control unit 'sees' open circuit and turns warning light on. Warning light stays on until next ignition switch off/switch on.

- Theoretically if oil really hot from engine being used hard, contacts may be open at time of ignition switch-on. Or, if parked facing up-hill, oil level will appear 'low'. The owner's handbook contains a clause to guard against this eventuality (!) - basically saying to switch off and on later.


Usual failure modes:

1. Resistance wire breaks, so open-circuit at connection terminals.
2. Contacts are bent/damaged/dirty, so not closed and no current through resistance wire, open-circuit at connection terminals.
3. Connection broken at terminals - i.e. dirty terminals, chafed wire.

In the case of the first failure, I don't think repair is possible. Remove sensor and check for open-circuit. Clean contacts through perforated shield with toothbrush and electrical contact-cleaner to eliminate possiblity of fault 2.

If someone shorts sensor wire to ground or shorts two wires together (in an effort to turn off the warning light), check control unit may be damaged. Verify if this is the case by putting a 12 Ohm resistor across the connection terminals. This should cause the light to remain off (and is the only 'safe' way to disable a faulty sensor). If light remains on with 12 Ohm resistor fitted, then check wiring and replace control unit behind instruments.

As you can imagine, I have experience of these sensors fitted to FIAT/Lancia applications. Some versions of the lowly Uno (70S, 70SX, some Uno Turbos) came with a check control panel; the oil level sensor was mounted on a special large tubular dipstick pushed into the standard dipstick hole. I imagine that one of these would provide low-cost repair parts for a 164 sensor. Resistance should be in the region of 12 Ohms if the sensor is not faulty (open-circuit if faulty).

-Alex
 

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Alex, does the brake light low fluid level sensor work on the same principle or is it just a contact/no contact thing on a float?
 

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Alex, does the brake light low fluid level sensor work on the same principle or is it just a contact/no contact thing on a float?
You got it with your float contact/no contact assumption :)

The ones I have seen have a float with a plastic pushrod that has a magnet inside the rubber 'press to test' bulb. When you push down on the rubber bulb, you are pushing the pushrod down. There is a glass reed switch (magnetic-field sensitive switch) soldered between the two wire terminals. Usually any fault is due to the reed switch coming adrift - it has to be really close to the magnet (magnetic field drops off as a square of the distance, so a millimetre really counts!)

I have also seen a broken reed switch due to the wire terminal being bent up. Fortunately the reed switch costs a few cents to replace (from an electronic components-shop, e.g. Jaycar - I see you're in Oz!).

There are a couple of different types of brake fluid cap in use - later ones where the wires come out on the same side, and early ones where the wires come out on opposing sides. They should be interchangeable for all intents and purposes, but usually you can repair what you have.

I find the fluid level sensor is useful for spotting brake pad wear - when the level light comes on, it's a good time to check how worn the front pads are (the pad wear causes a significant drop in the fluid level as the pistons rest further out in the calipers). This is assuming that you don't religiously top-up the brake fluid level...

-Alex
 

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I have new brake pads in my car (the dash was like a christmas tree before I started work) but the **** light is still on. I've double checked the fluid level, tried shorting across the terminals of the switch (although I suspect you need to do it at turn-on or something which I didn't do). It's still on. All the other lights are off (or bypassed like the coolant level one which I still can't get the float to float). Oops, hijacked the thread.
 

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2/ the dash "backlight" that illuminates the oil pressure gauge is dim making it difficult to read the gauge itself.. i'm sure i've read details on dash disassembly to replace faulty bulb (likely cause?), but couldn't find it when i searched.. anyone point me in the right direction?
For replacing dash lighting, start by picking-out the two legend panels for the dimmer/test and 'km' reset buttons. This should give access to the screws that hold the plastic strip below the instruments (lower steering column also). With that strip removed, undo screws through bottom of white instrument cluster frame. Cluster should now lift off two hooks in dash top. Note that outer vinyl 'hood' lifts off with instruments as an assembly.

I find the best tool to identify dash bulbs is an LED keyring-torch. Twist out bulbs and shine LED-torch through hole (I assume that in Australia, you use the word 'torch' to mean a flashlight, like we do ;)) Other giveaway is the sight of a green filter inside hole.

I like to rig up a bulb-holder with small wires soldered to the copper tabs and connected to a 12V power supply. That way, when I fit it into the instrument panel, the other illumination bulbs glow as well.

While you're there, you may like to do something about the awful odometer illumination. I found that cleaning the odometer drums (with methylated spirits) helped - the 'white' was very dirty. I cut back the black tin around the odometer (which didn't really help except to allow the 'km' marking to glow). Also I moved the odometer back in the housing by eliminating the rubber grommet mountings. I reasoned that if, while driving, the loudest noise in the interior was the odometer ticking over, then that would be a happy day indeed.

You may wonder why I bothered - I used to use my '92 164 for company-reimbursed night trips and I had to remember to keep a torch in the glovebox, until I made that improvement :)

-Alex
 

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