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Can not locate the heater vacuum line on 1999 gmc Sierra

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  • Bernie Derksen
    Bernie Derksen Dec 26, 2013

    We can not find the line off the canister or where it goes through the firewall. The mechanic says it comes off the side of the motor but there is no line there.


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  • Cars & Trucks Master
  • 3,103 Answers

There is a vacuum reservoirunder the hood.. its a canister type or a plastic usually has 2 lines on it is the main line one goes inside to the follows through the firewall to the interior of the vehicle..

Posted on Dec 25, 2013

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Posted on Jan 02, 2017

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SOURCE: 2003 GMC Sierra heater Blower wont shut off

My 2003 Sierra's blower came on by itself in the garage while I was sleeping and ran the battery completely down. I had to replace the blower switch located under the glove box next to the blower at the bottom of the right corner of the dash. The switch is in front of the blower and held in by two screws. Disconnect the two wire connections. This is a "dealer only" part and cost me 65.00. Also check the wire harness with seven wires connected to it for melted plastic. It will be marked "ABCDEFG". If it has melted, you'll need to replace it. Pay attention when reinstalling either part, that the wires "ABCDEFG" match the switch in that order.

Posted on Jan 17, 2009

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SOURCE: fuel pump fuse located on 1997 gmc sierra

The fuse is actually a Relay Switch and its located in the Fuse Relay Center on the driverside of the engine compartment. The Black Box is labled Fuse Relay Center, the diagram on the cap displays which Relay is the Fuel Pump relay...the Relay switch is usually $8-$15 depending on where you shop

Posted on Jul 28, 2009

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SOURCE: replace neutral safety switch on a 1988 gmc sierra

Typically the Neutral Safety Switches are located with the gear selector, either in the column or the floor.

Hope this helps,

Posted on Aug 21, 2009

  • 6 Answers

SOURCE: 2000 gmc sierra 1500 5.3 v8. a/c heater control problem

your heat/cool and vent selection options are controlled by engine vacuum through small clear tubes attached to the rear of your climate control interface. Other vehicles have small steel pull wires that operate the desired changes. You might try removing the trim and any fasteners affiliated with the interface/console. GENTLY pull outward and look to see if any of these tubes are pulled off or cut/damaged. Did anyone recently install a new stereo in the vehicle? If so, the vacuum tubing and or pull wires that change your outlets could have been damaged when the stereo unit was pushed into place. Hope this helps

Posted on Sep 09, 2009

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SOURCE: 1999 gmc sierra brake line diagram

I would join for free and they have most any diagram you will need for free for this vehicle

Posted on Sep 16, 2009

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Send symptoms of the problem in a comment if you are having an issue with heat and a HCV isn't installed on your vehicle...Guru...........Saailer

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I have a 95 gmc sierra and heat does not work. I havechanged the thermostat and the heater core what else could it be

You have a Valve on the pass side of the engine. It will have a small Vacuum line on top, and three water lines one of which goes to the heater core. This valve can get stopped up or the vacuum line falls off. Check that out. This valve lets the coolant flow into the core when open, or it by-passes back to the block.

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