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Unread 01-21-2014, 08:40 AM   #1
bootleg23
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Join Date: Nov 2010
Location: toronto, ont
Posts: 11
1998 XJ sport

Hey guys,

Issue with my HVAC.

when i put the knob from floor to either wind shield defrost or a setting where the AC compressor turns on (another mystery to me, but that's for another thread) on full heat regardless of fan speed the Jeep will make a loud annoying buzzing noise that lasts for about 5-10 seconds, and here's the kicker, to those who think its the AC compressor bearing.

1. the noise still continues when the engine is OFF.
2. the AC compressor was replaced 20 months ago.

everything works as it should, blows heat fine, blows AC fine, all fan speeds work.

The belt was replaced with a goodyear gator about 16 months ago.

If the noise is still there when the engine is off what could it be, some relay thats not fully engaging or disengaging?

this only happens when its set to a setting when the AC is enabled, blowing on the floor it doesn't happen (blowing ONLY on floor doesn't engage the AC compressor)

any help appreciated.

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Unread 01-21-2014, 10:41 AM   #2
CCKen
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1999 XJ Cherokee 
 
Join Date: Jul 2011
Location: Canton, MI
Posts: 1,903
Quote:
Originally Posted by bootleg23 View Post
Hey guys,

Issue with my HVAC.

when i put the knob from floor to either wind shield defrost or a setting where the AC compressor turns on (another mystery to me, but that's for another thread) on full heat regardless of fan speed the Jeep will make a loud annoying buzzing noise that lasts for about 5-10 seconds, and here's the kicker, to those who think its the AC compressor bearing.

1. the noise still continues when the engine is OFF.
2. the AC compressor was replaced 20 months ago.

everything works as it should, blows heat fine, blows AC fine, all fan speeds work.

The belt was replaced with a goodyear gator about 16 months ago.

If the noise is still there when the engine is off what could it be, some relay thats not fully engaging or disengaging?

this only happens when its set to a setting when the AC is enabled, blowing on the floor it doesn't happen (blowing ONLY on floor doesn't engage the AC compressor)

any help appreciated.
The AC compressor will engage when Defrost or Mix (Windshield/Floor outlets) is selected and the outside temperature is above 30*F.

To see if you can find the buzzing noise after the engine is shut down you may want to roll down your glove box and poke you head close to the opening and see if you can hear the noise.

Here's a pic through the glove box opening. In view is the blower relay and the HVAC vacuum harness disconnect. To roll the glove box down just remove the 2 rubber stoppers and the glove box will hang down on its hinge.



If the noise seems to be furher down, remove the kick panel below the glove box. It's held on with 4 fatsteners. The top fastener holes are slotted so you don't have to remove the screws, just the botton 2. Listen around this area.

.
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Unread 01-23-2014, 06:10 AM   #3
bootleg23
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Join Date: Nov 2010
Location: toronto, ont
Posts: 11
Ok thanks for the tip,

Ill go have a look when it warms up a bit, its -20 celsius out.

do you think its possibly that?

by very quickly listening when it happened it seems like it was coming from under the hood.

anyway ill report my finding in near future.
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Unread 01-23-2014, 09:13 AM   #4
CCKen
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1999 XJ Cherokee 
 
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Location: Canton, MI
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Quote:
Originally Posted by bootleg23 View Post
Ok thanks for the tip,

Ill go have a look when it warms up a bit, its -20 celsius out.

do you think its possibly that?

Not necessarily. Just giving you some areas to check if you think the noise is coming from under the dash (HVAC related).

by very quickly listening when it happened it seems like it was coming from under the hood.

anyway ill report my finding in near future.
.
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Unread 01-25-2014, 08:34 AM   #5
tsc
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2006 LJ Wrangler 
 
Join Date: Mar 2007
Location: Pacific Northwest
Posts: 514
That right black block in your photo is a relay- unplug it and see if still does it- it could the relay vibrating.
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