bigredodge

ok guys needing some help here as I am not the best with electrical systems (but learning a lot very fast).
problem:1) ac compressor not kicking on w/ac.
2) ac compressor relay #30 pin (brown wire) is cut

with that being said, this is an obvious electrical issue. (I think lol)

when I got the truck: #30pin brn wire was capped together with red wire w/ black tracer going to bulk head which then goes to ignition switch. I do not recall if the compressor ever worked this way (part of my problem) BUT compressor looks brand new.
what I have done: ignition 40amp fusible link fried (short I fixed)
ac 40amp fusible link was already fried (previous fixed by capping wires directly I guess?)
installed maxi fuses in place, connected red w/black tracer and Brn. wire after 40amp maxi fuse.
ac off try to start truck, instantly blows ignition maxi fuse, ac doesn't blow at all.
remove brown wire from the fuse leaving red w/blk. fused.
truck starts, ac blows, compressor does not kick on but no blown fuses.
rig brown #30 directly to battery, relay doesn't click still.
removed relay tested w/ 9 v bat. + to #85 or 86(- to the opposite) and it clicks so relay good (?).

what am I missing? my wiring harness is nearly completely exposed because I have been working on these electrical issues and have resolved all but this one.
where does this brown wire need to be for the compressor to work I can't find this on any diagrams etc. have traced wires everywhere. I'm missing something and would appreciate some help.
thanks
big red

maybe368

Does it have any pressure? There is a low pressure cutoff switch connected to the block on the passenger side by the big black heater thingy. Disconnect the wire and jumper between the 2 contacts. If the compressor comes on, the gas is low, if not, you have other problems and we can o from there...Mark

bigredodge

ok will check asap
does that have something to do with the brown wire on the relay?

maybe368

Not really, maybe I misread your second post, I thought that the system came on, but the compressor didn't. If there is still an electrical wiring problem, this may not tell you anything. If you have gauges, you can check for pressure that way..Mark

bigredodge

update: tried jumping a 2 prong plug, blew a 20 amp dome light and windshield wiper fuse, replaced fuse.
tried jumping between another 2 prong plug got nothing
jumped trigger terminal on relay plug directly to battery, something clicks sounds like it starts to move (whatever it is) then it stopped thought maybe I have to start the truck and turn ac on. went to start blew my 40amp ignition maxi. got mad swapped 40amp ac maxi into ignition spot and started truck to move it in the shade, started fine and idled for about 5 seconds and died, ignition maxi fuse blew again. out of maxi fuses and no idea why it blew that second time, didn't have anything jumped etc. normally it will run fine.
will update later when I can get to town for more maxis.

maybe368

Sounds like a dead short somewhere. I assume that you have already dealt with the fusible links? Electrical gremlins suck,especially when someone has hacked it up...Mark

bigredodge

yes definitely electrical. brown wire from ac compressor relay is not plugged into anything. found a connector for my windshield wipers that's not plugged into anything.
I'm not finding any shorts, im at a loss here.

maybe368

What year is your truck? I have a 90 FSM and I'll look for you if it is the same...Mark

bigredodge

it's a 92 d350. thanks but I do think they changed them up a bit 91.5 right?

j_martin

There's a link to a 91.5 electrical diagrams set in the FAQ section of this forum. That's the diagrams you need.

bigredodge

found the diagrams thanks

is this the relay?? also what does "natural" mean?

bigredodge

ok now my ignition fuse is blowing with ac off and just flipping the ignition to on/acc... guess air conditioning repair is on hold until I figure out where this short is.

I have a high end maxi fuse block in place of ignition and ac fuse links each on a 40 amp maxi

maybe368

That could be something as simple as the ignition switch. Don't know about the later trucks, but mine is on the steering column and is pretty easy to change out. I don't see how it could be the lock cylinder because it just actuates the switch...Mark

bigredodge

the ignition switch itself could be causing this? i did buy a cheapo from oriellys. how would i test it to see if its shorted? i have been tracing ignition switch wires and dont see any cut, pinched or shorted wires

maybe368

If it has messed itself up inside sure. Think about it, you said that just by turning on the switch, it blows. It could be just energizing the actual short else where or it could have an internal fault that takes it to ground. They are not that expensive and the easiest way would be to replace it with a quality switch and see what happens. I don't like throwing parts at problems, but in this case it may be the easiest thing to do.I like rockauto because they generally give you multiple options for quality. Dies everything move smoothly when the switch is turned?...Mark