Technical Tips > Electrical-Electronics-Air-Lighting-Guages-Security-Vacuum

C4 1990 Electrical Ccts FSM

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bfit:
Someone said to me once that there only switches.
Bfit

Vettech:
Yes well said Bfit, there is nothing like "Boolean Logic".
Which is like getting thru a Gate or two or is it like jumping thru hoops?

Needless to say I'm home now, and referring to the Gospel according to GM - it shows that the seat belt switch is an "NC" contactor.
Supplies earth to the Audio Alarm Module's A2 input (C4 84~89). A quick glance at the cct below shows that AAM then switches or flashes the "Fasten Seatbelt Lamp".

Once belt is buckled, the cct is opened and removes the earth from the "A2" input. Which now answers another question, the loose plug in the centre console, its open cct, ergo no seat belt alarms, since I need to get under LH footwell to restore relays & fittings etc back to normal, I'll remove the seat for ease and double check the seat belt fitting to ensure there is no switch.

Vettech:
Any members out there with a GM 1990, 91 or 92 Electrical Diagnosis Service Manual Supplement, or if you have seen one for sale in Oz or could lend me. I have the 87 book, but as you all know the C4 Series 2 commenced in 90 and included a lot of changes esp in the electrical, electronics and dash/consol and wiring.

Please let me know, with warmer weather, I'm about to pull the RH seat out to find/fix these nagging irritating intermittent electrical faults. Untill found I suppose ill just have to be the passenger in the wifes Mustang. Of couse it also depends upon my latest bout of Gout in the right knee - which does tend to knobble ones movements, esp those requiring one to crawl head first upside down under the dash.

Vettech:
OK a big thankyou once again to Uncle Burton (batee.com)
Always very helpfull.
He had some 90 circuit diagrams, see one attached.

My "security Indicator" is currently not working, and is one of several iritating minor electrical issues. I suppose we will start with the fuse and work our way to the globe. I'll get a pic of the "under dash" layout soon - this will give you an idea of the mess created by converters that us owners have to put up with.

Hopefully a wire, connector or splice, if its the bulb, then out comes the Instrument Cluster, and at this stage of disassembly it may just take four (4) more screws and it should unplug and pull out  - of course once out, we may as well go over it and check everything.

Of course this is the simple side of the probable cause, the Central Control Module (CCM) switches this lamp on and off, and requires "X" number of inputs on its gates to give the desired response, so the search may become more involved.

sirfixalot:
to check the fuse Doug just see what also is on same fuse. My first point to test after fuse would be to remove instrument cluster you then can test to prove + & - sides of circuit

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