WERE CAN I FIND THE CRIRCIT FROM THE HEATER, OR THE FUES BOX

open glove box , see users guide, read it, , page index FUSE
or google it find it easy,well 1987 no digital copies then 35 years old.
or read the service manual

https://eautorepair.net/Marketing/Default.asp

hood box and cab box
google this find answers, for sure 35year old, super rare paper books.
they show up time to tom fleabay.
bests both books.

it should tell you on the back of the fuse cove

YOU CAN PULL EVERY FUES WITH NEEDLE NOSE PLIERS WONT TAKE BUT 5MINS OR SO YOU MIGHT FIND OTHER ONES BLOWN..SOMETIMES IF ALL FUES ARE GOOD THE LIGHTER SOCKET GOES BAD OR THE LIGHTER GOES BAD

Hi,if you know where the fues box is your half way there.
just buy a electricle screwdriver that has a light inside it with a wire that has got a crockerdile clip on the end,
put the cockerdile clip on a earth the body of the car,
then look at the fues on the top of the fues there is two little bits of metal these are where you will put the screwdriver blade to,
if yoy put the ignition on then go back to the fuesestuch one side of the fues on the little bit of metal the screwdriver should light,This is the power side,now if you tuch the screwdriver on the other bit of metal the light should come on again,if it dose the fues is ok,
if not the fues is falty(replace fues)do this to all the fueses and you will find the fues that is falty.
all the best.

you need to take all the fues out then blow dry the fues box once dry put the fues back were there belong.

sounds like you have water in fues box, best thing i can think of to get it sorted is disconnect the battery get a large can of wd40and give the engine bay a good dowsing in it, all over the fues and fues box wires arround it, do all the alternator to and leads (if not deisel) leave it for about 30 to 45 mins ( dry period) then reconnect the battery and see how it goes, if no luck first time, repeat....hope this helps

FUSE PANEL IS ON DRIVER SIDE UPPER LEFT OF THE BRAKE PEDAL VERY HARD TO GET AT,YOU NEED A FUES PULLER TO REMOVE FUES. DUMB PLACE FOR FUES BOX!!!! I HAD A 93 BLAZER,,GOOD TRUCK LASTED OVER 500,000 KM.

Replace the ing. lock cylinder and chip key

Check your fuse box to make sure the fues didnt blow. the fuse box is located on the dash on the driver side door.

could be a wiring problem get a test light and test it