Flasher/Warnings CPU

[Casey]

That just leaves the last circuit connecting to pins A, B, F, H and L on the module. I cannot find any reference to these pins in the Mazda wiring diagrams!!

Eureka! I got a Japanese speaking friend of mine to translate the Japanese text on the silk screen print on the "mystery" part of the circuit board:

20210622_162125.jpg (110.79 KiB) Viewed 10984 times

He came back with "intermittent wiper"

I had already worked out there was a set of conditions I could apply to this particular circuit which left the relay "on" for 2-3 seconds after removing the condition, so that made perfect sense. The relay directly operates the power to the wiper motor.

On rechecking the Mazda wiring diagrams and found this:

Wiper circuit.JPG (42.45 KiB) Viewed 10984 times

So I now know where the module pins A, B, F, H and L connect

If anyone has any problem with the "single wipe/wash" or intermittent wipe, but the normal wiper functions normally, it'll most likely either be the switch contact or this part of the module that is the culprit.

I've ordered some parts to start putting together a text box and Pete has kindly put a module connector in the post to me, so all looking good.

It's been an very interesting and enjoyable challenge to reverse engineer this module

[ian65]

Really interesting stuff Malcolm, I never knew the intermittent wash wipe went through that module

[Casey]

Nor did I - I was very surprised to discover that!

[Casey]

I have now completed and tested a prototype circuit which is capable of plugging into the hazard unit to operate all the functions - thanks Pete for the donated plug . Next job is to check I have all the bits lying around to construct a proper test box.

BTW, kiwidave kindly lent me his CPU module to reverse engineer and design the tester. Everything except the 30 sec "ignition barrel illumination function" seemed to work. If you look back a page to the rough cct diags I discovered two transistors (Q5 and Q6) had blown. I replaced those with some similar spec NPN transistors in my collection and it's all working again - very satisfying

To summarise, this module does the following (in the UK version):

1. controls the indicator and hazard light flash timing
2. operates the ignition barrel illumination light for ~30 secs after a door is opened, until the ignition goes live.
3. controls the intermittent wipe and single wash/wipe.
4. operates an intermittent warning buzzer in the dash when the lights are on, the door is open and the ignition is off.

[ian65]

Brilliant work Malcolm, first time in 30+ yrs I’ve actually understood what controls these functions. Excellent stuff

[ian65]

While you’re on a roll... what does the cpu under the plate in the passenger footwell control?

[Casey]

That's the emissions control gubbins

[Casey]

Prototype tester works a treat - diagnosed a dodgy connection on one pin which controlled the intermittent wipe. Contact cleaned and all good

So, Dave, can you recall what problems you had which caused you to change out that module?

[KiwiDave]

The intermittent wipe was one although I had no idea that the flasher CPU was involved with that. I would turn on intermittent wipe and it would wipe once or twice intermittently and then no more.

The reasom I changed it out was a background hum / squeak which would occur from startup particularly in cold temps amd would disappear eventually. I traced where the sound was coming from, disconnected the unit and the noise stopped. I just happened to have a spare one in storage and that does the same thing but not nearly as frequently.

[ian65]

That's the emissions control gubbins

So if a car had a rats nest delete and the nikki taken off then this cpu is obsolete?