SirVelociraptor

So I've had a couple of really annoying electrical bugs pop up over the past few days that I'm having trouble tracking down. First off, a little background info that might be pertinent, last month I replaced the entire gauge cluster in my car (the previous owner skillfully cut a nice, jagged, kind-of-rectangular hole into it for an aftermarket radio and unfortunately, the dash is one big piece of molded plastic), however I re-used all of the electrical components from my original dash (climate controls, blower switch, the PCB mounted to the back of the gauge cluster, everything) and they all worked without issue beforehand. Anyways...

The first issue is the blower speed. About a week ago if I had it on Medium-High it would just switch into High on its own. Sometimes it would go back to the original speed after a varying amount of time and sometimes I had to switch the climate control off and on again to get it to operate normally again. However now its pulled a complete 180 on me and will now ONLY operate in Medium-High, even if I switch the climate control off entirely. The only time it stops running is when the key is switched off. Putting the blower switch to High or the climate controls to Max AC will still switch the blower relay and engage High speed, however.
^ (Possibly a bad blower resistor?)

The second and arguably more annoying issue I'm having is that the Instrument Cluster bulb fuse has started blowing. So far it's blown the original 4 Amp, a 5 Amp and even a 10 Amp fuse. It's not instantaneous, the bulbs will work for a few minutes, but it's still a matter of when, not if, the fuse will blow (and man, is it an annoying one to change).

I know the PCB that holds the gauge lights and the under-dash lamps are clean, not corroded and not melted. Likewise the ash-tray, glove box and clock lights are all clean and okay, so I doubt it's a short at or near the sockets. Could it be the dimmer or headlight switch?

If anyone has any pointers on where else to look for these issues, it would be appreciated.

Olds64

If you're blowing fuses there's a short in the circuit somewhere. I experienced this with the interior lights in my 71 after having my interior redone. It turned out there was a sheet metal screw that pierced one of the light wires near the package tray.

If you're having trouble with the fan speeds you might look at the resistor on the AC box in the engine bay. Oldsmobile used that for years and it sometimes goes bad.

SirVelociraptor

Is it possible the dimmer in the headlight switch has gone bad, causing a short? I know a short in the feed for the Instrument Lamps is a likely cause, but I woupd really prefer to check everything else off before contorting my way around the underside of a dash trying to trace a wire.


The resistor was my first thought too, however it was fine. Turn out it was the fan speed selector switch. Something happened internally causing it to constantly send 12v down the wire for Medium-High speed. Thankfully I had a spare from the replacement dash.

cjsdad

Something that happens a lot when aftermarket stereos find themselves in GM cars is the dash light wire gets mistaken for a ground wire. Make sure the grey wire is not grounded at the stereo/radio location.

SirVelociraptor

Now here's something to scratch your head over; Ever since I replaced the blower speed selector switch, not only has the blower behaved and stayed at the speed I set it to, but the Instrument Cluster bulb fuse has not blown. So somehow the Medium-High blower speed had become bridged with the power feed (or ground) for the cluster lights, causing the fuse to blow and the fan to constantly run at Medium-High. I have no idea how that happened, but in some way or another it did. Here's to hoping it doesn't happen again.