Heated mirrors without rear defrost

MountaineerTom · July 16, 2004

My truck does not have a rear window defoger or heated mirrors. I have a set of Tahoe mirrors with the puddle light on the bottom that I'm going to be installing sometime soon. Both have heated mirrors. I was originally thinking I would change the mirro glass over and put my non-heated ones in. However, I "think" the harness is prewired for heated mirrors. I'm thinking of checking ot the harness that plugs into the a/c and heat contols to see if it appears to be prewired as well. If so, I may get a set f controls with the defrost button and see if I can get the heated mirrors working.

My question is, if the harness that goes back to the rear window is prewired, would I have any electrical problems (mainly a fire hazard) from those wires when I push the button to make the heated mirrors work, since I don't have the defroster on my rear window?

Thanks.

atomoverride · July 16, 2004

you shouldnt have any issues...but you might need to get your computer reprogrammed. Best thing to do is check with your local gm dealership.

I would think if you dont have the rear defroster button you can just pickup a unit from the junk yard and plug it in.

99-2door · July 16, 2004

You shouldn't have any problem with any exposed wires, because the harness that goes to the rear window is different for ones with the rear defogger. The harness plugs in at the center under the dash in the driver's foot well.

GnatGoSplat · July 16, 2004

Your truck should be prewired and there shouldn't be any fire hazards because all connectors are insulated.

MountaineerTom · July 17, 2004

Outstanding. Thanks for all the info.

I kind of figured it would be ok, but wasn't sure.

MS3DALE · July 17, 2004

I TRIED TO ADD THE HEATED MIRRORS TO MY '99 SILVERADO WHEN I HAD IT AND BOUGHT THE HVAC CONTROLS FOR THE RR.DEFOG. BUT THE MIRRORS WOULD NOT WORK,I WORK IN THE PARTS DEPT. AT A CHEVY DEALER AND THE DOOR HARNESS PARTS NUMBERS ARE ALL THE SAME NO MATTER WHAT MIRRORS YOU HAVE SO I DON'T WHATS DIFFERENT BUT THEY WOULD NOT "HEAT"

JUST THOUGHT I WOULD LET YOU KNOW.

GnatGoSplat · July 17, 2004

Oh yeah, you also have to add a relay underhood to make the mirror heaters work. I almost forgot about that.

MountaineerTom · July 18, 2004

Oh yeah, you also have to add a relay underhood to make the mirror heaters work. I almost forgot about that.

Is one that gets added in the under fuse electrical center, or an aftermarket one mounted under the hood?

Thanks for any details.

Dex857 · July 19, 2004

its a factory relay. its for the rear defog. It controls the mirrors too.

look in a junkyard.. GM wants about 20.00 for it. I did the same thing you are doing. Works good.

MountaineerTom · July 19, 2004

its a factory relay. its for the rear defog. It controls the mirrors too.
look in a junkyard.. GM wants about 20.00 for it. I did the same thing you are doing. Works good.

I havn't looked under the hood yet, put is it the same shape as a regular relay that you can buy at a parts store for, say foglights?

GnatGoSplat · July 20, 2004

No, the standard auto parts store relays fit Bosch style sockets which have larger terminals. The GM ones are the same physical size, but have very small terminals.

Junkyard is your best bet, just poke around late model GM's. They actually come in 2 sizes with the same pinouts, a smaller rectangular size and a larger square size. I got a larger one. I was able to get one out of a 96 Monte Carlo ABS system.