AC on high, lights go out - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Inthuwind · 11-28-2014, 07:41 PM

I would like to know why my lights go out when I turn my AC on high. The fuse does not blow and when I turn the AC off for a few minutes, the lights will come back on. What causes this? And how do i fix it? I have a 140am Powermaster alternator, also a Mark VIII electric fan in my truck. Any other info needed? Thanks in advance.

_Ogre · 11-28-2014, 07:57 PM

chances are that your ac is on the same circuit as your headlights
there should be an auto reset breaker in your headlight circuit, it opens when the load is too big
change where you feed the ac circuit, the headlight circuit is for headlights

Inthuwind · 11-28-2014, 08:16 PM

That's what I was thinking, it has an aftermarket wiring harness and AC, so I'll see where they tied in. There should be a separate circuit off the harness for AC, shouldn't there?

_Ogre · 12-06-2014, 03:33 PM

there is a heater fuse, my vintage air unit has a separate 30 amp feed from the battery for main power
i used my heater fuse for my alarm system

11-28-2014, 07:41 PM	#1
Inthuwind Straight jacket required Join Date: Oct 2003 Location: OKC, OK Posts: 882	AC on high, lights go out I would like to know why my lights go out when I turn my AC on high. The fuse does not blow and when I turn the AC off for a few minutes, the lights will come back on. What causes this? And how do i fix it? I have a 140am Powermaster alternator, also a Mark VIII electric fan in my truck. Any other info needed? Thanks in advance. __________________ 1968 C10 Short Stepper 350/350 A/C P/S P/B Front disc 3/5 static/ 12bolt rear 3:73 1979 Pontiac Trans Am 10th Anniversary/455/4spd 2011 H-D Street Glide - CAMMED n lowered Dad always said,"Son, if you can't be good...be good at it."

11-28-2014, 07:57 PM	#2
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,677	Re: AC on high, lights go out chances are that your ac is on the same circuit as your headlights there should be an auto reset breaker in your headlight circuit, it opens when the load is too big change where you feed the ac circuit, the headlight circuit is for headlights __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer

11-28-2014, 08:16 PM	#3
Inthuwind Straight jacket required Join Date: Oct 2003 Location: OKC, OK Posts: 882	Re: AC on high, lights go out That's what I was thinking, it has an aftermarket wiring harness and AC, so I'll see where they tied in. There should be a separate circuit off the harness for AC, shouldn't there? __________________ 1968 C10 Short Stepper 350/350 A/C P/S P/B Front disc 3/5 static/ 12bolt rear 3:73 1979 Pontiac Trans Am 10th Anniversary/455/4spd 2011 H-D Street Glide - CAMMED n lowered Dad always said,"Son, if you can't be good...be good at it."

12-06-2014, 03:33 PM	#4
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,677	Re: AC on high, lights go out there is a heater fuse, my vintage air unit has a separate 30 amp feed from the battery for main power i used my heater fuse for my alarm system __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer



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