Cigarette Lighter and Blower Relay Wiring Questions
 

I have a 1971 Jimmy that I discovered the cigarette lighter had stopped working. Related to that I believe after investigating and doing some research, recently I noticed a burning smell when the heater blower speed was set on high. It goes away on lower settings. Anyway when I looked at the cigarette connection on the fuse panel I found that connector (orange wire) had some melting. I replaced the connector but the red wire at the back of the lighter still doesn’t have power.

That led me to doing some research and I found the first photo below on a different forum post. It shows both an orange wire and red wire at the CIG fuse panel connection. The second photo is my panel. You can see it has only the orange wire (blue arrow) however, there is also a separate red wire (yellow arrow) I found disconnected that I thought might be the power to the lighter. I connected it to the fuse panel at the post that is directly below the cluster connector (red arrow, it has unswitched power) but still nothing at the lighter.

Anyone have any ideas on what could be going on here? The lighter worked until it didn’t. I hadn’t removed or disconnected any wires at the fuse panel. One thing I found strange is the CIG connection is unfused. Is there a fuse or fusible link somewhere else? I tried to trace the red wire back from the lighter but it disappears behind the dash panel and I didn’t want to pull the panel until I had some answers to my questions.

Thanks in advance for any insight.

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

Its my experience that GM typically doesn't fuse the cigarette lighter which can be problematic. I had a lighter short out internally while driving down the freeway in my old S10.

I don't smoke and never used the lighter but out of the blue one day smoke starts billowing out from the dash area where the lighter is. Needless to say I made a sharp right to the side of the road and started tearing wires out of the dash.

I believe that the cigarette lighter and the high speed fan power can share the same connector at the fuse panel. The link explains the circuit as well as has the wiring diagram.

http://67-72chevytrucks.com/vboard/s...d.php?t=705082

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

So to follow-up and close this post: today I looked closer at the disconnected red wire near the fuse panel and to me it just had to be the lighter wire. I reconnected it to the same blade as yesterday that I thought was constant 12 volts, turned the ignition to Run and was happy to find power to the lighter. I then connected the red wire to the piggyback connector on the orange wire (high blower relay), installed an inline 20 amp fuse to protect them and called it good. I feel much better having this relatively high-amp wire protected. No more melting!

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

The lighter circuit is protected by the large fusible link in the main harness by the battery.

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

No melting is good! Best to keep the smoke inside the wires so everything works. :lol:

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

If that’s the case wouldn’t the blower relay circuit also be protected since they get power from the same blade on the fuse panel? If so why did I experience melting on the relay fuse panel connector?

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

The nature of fuseable links is that they are a slow blow type of fuse. Meaning that if it is rated for 30 amps once exposed to 35 amps it may take as long as a minute to blow where a fuse would blow in a matter of seconds.

In your case both the fuseable link and the wiring at the fuse block were heating up simultaneously. You were only able to smell the wires in the cab.

I would recommend doing a physical inspection of the fuseable link by bending or flexing the fuseable link looking for stiff or ridged areas. When a fuseable link fails it shouldn't show any signs of overheating. So flexing and stretching the link should allow you to detect any melting of the conductors inside.

Another possibility is that someone in the past replaced the factory fuseable link with an incorrect wire that doesn't protect the harness.

I posted some information on fuseable links in post 469 in the link

http://67-72chevytrucks.com/vboard/s...or#post8564169

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

Good information, thanks for sharing. I have just enough electrical aptitude to scrape by with help from others like yourself.

I inspected the fusible link and it seems to be in satisfactory condition. Supple without any outward signs of damage and it’s smaller than the wire it’s connected to, though I don’t know the gauge of either. Nonetheless at least the blower relay and lighter circuits are protected now with the fuse installed.

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

Isn't the blower circuit supposed to run through the fuse labeled "HEAT" below the radio terminal?
A 14Ga wire to the heater switch (allegedly brown) on my diagram

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

On non-AC trucks the Heat fuse supplies 12dc positive to the blower fan in all speeds. As shown by the brown wire the drawing. See link for drawing

On AC trucks the heat fuse only supplies 12dc positive to low and medium speeds. (The brown wire again) High speed comes from the fuse box (Orange wire) like shown in the photos above. Link also shows AC addendum to main harness drawing.

http://67-72chevytrucks.com/vboard/s...d.php?t=705082

Re: Cigarette Lighter and Blower Relay Wiring Questions
 

Thanks. I bookmarked that page, but forgot it existed ;-)