Light for AC/Heat Control - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ratman90 · 03-30-2020, 11:32 PM

So I am working on 72 C10. Redoing a bunch of dash and gauge work.
Replaced some gauges and bulbs, replacing the AC/Heat controls and cables.

I see my control unit has a place for 2 bulbs, one on each end. I see i have one bulb socket, but also have another wire cut that i thought was hot with dash lights on so I bought another bulb socket to splice on and have 2 LED bulbs in AC controls.
It is ign hot though.

That being said, has anyone spliced into that other bulb line and run two lights to the AC controls? Any reason why not?

That ign hot line is coming from the IGN hot tap in fuse panel, maybe for former radio power.

THoughts on 2 bulbs since I have the extra socket and led bulb?

Larry

**dmjlambert** · 03-31-2020, 12:37 AM

The A/C-heater control light bulb wire should be a grey wire that gets its voltage from the instrument cluster grey wire. You can test for presence of the right switched power with a test light or multimeter. Yes, you can tap into that wire for both bulbs. If you don't see that grey wire set up, I recommend connect both A/C control light bulbs from a new grey wire that you plug in to the fuse panel. If you plug it in to the terminal marked PNL LTS (notice the little arrow pointing to the terminal), it will be the same source of power the instrument cluster gets, which works when the lights are on and twisting the headlight switch dims the cluster and A/C control lights. LED bulbs are not usually dimmable, or if they do dim, they don't dim very much before just going out.

Andy4639 · 04-04-2020, 09:23 AM

All AC controllers had 2 bulbs which are grey wires coming from head light switch. They turn on the dash lights when the head light switch is pulled out.

Heater controller only had 1 bulb wire which is grey also.

There is no problem splicing into the grey wire and running 2 bulbs.

ratman90 · 04-04-2020, 12:23 PM

Awesome that's what I was hoping to hear. I will splice into that other one and add some length.

The other wire coming of ign hot was probably a leftover from one of the PO for a radio.

This truck was a gift to me, bought at auction and is a train wreck.

Yes it drove across the auction block. With gauges glued up to look l9ke they worked.

Crazy stuff under this dash.

Thanks
Larry

03-30-2020, 11:32 PM	#1
ratman90 Registered User Join Date: Jul 2017 Location: Longmont, Colorado Posts: 64	Light for AC/Heat Control So I am working on 72 C10. Redoing a bunch of dash and gauge work. Replaced some gauges and bulbs, replacing the AC/Heat controls and cables. I see my control unit has a place for 2 bulbs, one on each end. I see i have one bulb socket, but also have another wire cut that i thought was hot with dash lights on so I bought another bulb socket to splice on and have 2 LED bulbs in AC controls. It is ign hot though. That being said, has anyone spliced into that other bulb line and run two lights to the AC controls? Any reason why not? That ign hot line is coming from the IGN hot tap in fuse panel, maybe for former radio power. THoughts on 2 bulbs since I have the extra socket and led bulb? Larry __________________ 1972 C10 LWB 2WD 307 4 speed Rescued from Field July 2017

03-31-2020, 12:37 AM	#2
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 3,563	Re: Light for AC/Heat Control The A/C-heater control light bulb wire should be a grey wire that gets its voltage from the instrument cluster grey wire. You can test for presence of the right switched power with a test light or multimeter. Yes, you can tap into that wire for both bulbs. If you don't see that grey wire set up, I recommend connect both A/C control light bulbs from a new grey wire that you plug in to the fuse panel. If you plug it in to the terminal marked PNL LTS (notice the little arrow pointing to the terminal), it will be the same source of power the instrument cluster gets, which works when the lights are on and twisting the headlight switch dims the cluster and A/C control lights. LED bulbs are not usually dimmable, or if they do dim, they don't dim very much before just going out. Last edited by dmjlambert; 03-31-2020 at 12:38 AM. Reason: spelling

04-04-2020, 09:23 AM	#3
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Light for AC/Heat Control All AC controllers had 2 bulbs which are grey wires coming from head light switch. They turn on the dash lights when the head light switch is pulled out. Heater controller only had 1 bulb wire which is grey also. There is no problem splicing into the grey wire and running 2 bulbs. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

04-04-2020, 12:23 PM	#4
ratman90 Registered User Join Date: Jul 2017 Location: Longmont, Colorado Posts: 64	Re: Light for AC/Heat Control Awesome that's what I was hoping to hear. I will splice into that other one and add some length. The other wire coming of ign hot was probably a leftover from one of the PO for a radio. This truck was a gift to me, bought at auction and is a train wreck. Yes it drove across the auction block. With gauges glued up to look l9ke they worked. Crazy stuff under this dash. Thanks Larry __________________ 1972 C10 LWB 2WD 307 4 speed Rescued from Field July 2017



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