1978 Caprice fuse help, please.

[patticake91356]

My husband is restoring his mother's 78 Caprice. Everything works except the door locks, horn, and cigarette lighter. He has checked all the fuses he can find and swares there must be another fuse box someplace. Are there two fuse boxes and if so where are they. Also, is there a place I can get a picture of the fuse box and what each fuse is for? He can't find the owner's manual right now. Thank you.

[randy78]

those are three different systems

only one fuse panel in these cars


the horn uses a relay it is rectangle and three spade plugs into the panel like the turn signal and hazard flashers do

the locks have a relay and also a circuit breaker

are two circuit breakers in the fuse panel, both metal and a little bit bigger than blade style fuses


can be a bad lock door switch

will have to us ea process of elimination to figure out what is wrong with each system

cigar lighter commonly fail because they are simply old and junk

make sure it is hot in the center and ground around the inside of the socket) all the metal) with a test light

make sure the horn wire at the cap is getting ground from the horn cam that runs around the steering column under the steering wheel

you will ahve to understand how these systems work and wire colors for each to figure out why they are no longer working

usually it is a component that has failed

almost always

unless visual wiring damage is seen or found

suspect switches and components and harness plugs first


the horn wires are dark green

they will be ground when the horn button is depressed

the cigar lighter is black and orange normally

orange hot all the time

make sure grounds are good

on the driver side under the end of the dash at the door pillar frame there are black ground wires and a blade connector screwed to the car metal that ground wires are plugged onto
make sure they are all good

if the circuits show hot in the fuse sockets, on both sides of the fuse

if not hot on one side with fuse installed, or no hot on either side fus einstalled or not then you have a feed problem or key needs to be on to run that circuit

no key needed for locks and cig lighter

or horn even

so..

if you are missing hot or ground in any of the circuits then check relays and breakers and switches and so on

[Blue Bowtie]

Originally Posted by patticake91356

...Everything works except the door locks, horn, and cigarette lighter.

If it's like the older (early '70s) B-cars, the CTSY fuse gets its power from a wire attached to the horn relay B+ (battery power) feed. Solve the horn problem, and the lighter and locks may also work, since they are all on constant power. There is a fusible link feeding the horn relay. The relay should have a constant +12 VDC whenever the battery is connected.