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Brake fluid level indicator - DIFFERENT WIRING

875 Views 0 Replies 1 Participant Last post by  SpiralArchitect
Early models (I'm not sure if this will apply to any car sold in the USA) do not use a relay to close pins 7 and 8 on ALFA ROMEO CONTROL N22B. The schematic on Cardisc doesn't apply.

If both wires at brake fluid level switch H17 are orange, that is the early wiring.
Switch H17 is wired through G150 to N22B pins 7 and 8 and closes them directly when full. Relay I72 doesn't exist.

The H17 switches of early and late models are different and incompatible as the late model closes when empty.

Although there are "low fluid" and "worn pads" lights, both circuits trigger both lamps at the same time. There is absolutely no way to tell if the fluid is low or the brake pads are worn without checking.

This is to remind that the rear pads don't have indicators and low fluid is the real warning. It also ensures that a blown bulb won't stop a warning from being displayed.

These lights will energize in the following conditions:
- front brake pad wear;
- brake pad indicator circuit open;
- brake pad indicator circuit grounded;
- low brake fluid level;
- fluid level indicator circuit open;
- fluid level indicator circuit grounded (as opposed to late model where grounding the circuit causes the relay to open its contacts);
- N22 fault.

Whenever these lights come on and the cause is unknown check that the fluid level and pad wear circuits are closed at N22B and both are isolated from ground.

Level indicators can be rebuilt easily. To take the switch apart simply remove the orange cap, press out the two contact tabs and pull the stem out. Remove the contact washer and polish.

If the pad wear indicator circuit is grounded, check if the insulation at the pad is damaged. I found out that brake pad dust can bridge an exposed wire to ground (my pads are conductive) and cause the light to come on. A voltage check works better than a resistance check in this case but do disconnect N22B before commencing.
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