NEED HELP Suburban popping sound

LVJJJ

Active Member
#1
Just driving along, all of a sudden a loud popping sound began coming out of the passenger side of the dash board. It is loud and rhythmic, pop, pop, pop. I thought it was something from the radio coming thru the dash speaker, but isn't, disconnected the speaker, didn't stop. The only electrical thing in that area I can think of is the computer. I have added a "FastChip" that increases power at WOT for towing. However, what component in the computer would be to vibrate able to make a sound?? Truck runs fine so maybe not computer.

I also thought it might have something to do with the windshield washer pump as that is rhythmic when it runs. Recently ran out of washer fluid, wonder if that has something to do with it. Help.

btw. its a 1994 GMC k1500, SLE
 

MRRSM

Lifetime VIP Supporter
#2
If the sound emanates from under the Dashboard... it probably has something to do with one of the HVAC Blend Door Actuator(s) going bad on or near the Evaporator Coil Blower-Fan Box Housing. It would be best if you have a Genuine Service Manual to get to it and do this PITA R&R. These Videos will illustrate the 2 repairs:

"My Wife is SOoooo Annoying......I Mean she is SOoooo Annoyed..." LOL


 
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LVJJJ

Active Member
#3
MRRSM, thank you sooooooooooooo much. Knowing what it is that's causing the problem is 90% of the solution, well in this case cause its under the dash, maybe 50%. It does sound like a gear is slipping.
 

MRRSM

Lifetime VIP Supporter
#4
You are Welcome, Brother... Perhaps just using the solution on Video#1 and side-stepping all that unnecessary labor will do the trick ...if you live where it does not get too cold. But ...if it comes down to cases and you need to follow a similar path as in Video #2... Please remember these suggestions:

(1) While working in such cramped quarters... it will be very easy to get frustrated and impatient and this could make for twice as much work for yourself by having to "Break your way in..." to get access to the damned Blend Door Actuator. Taking Frequent, Short "Breaks" will prevent such problems in the rush to get in and out. The MORE Haste...The LESS Speed.

(2) Try to ensure that you have EVERYTHING you'll need well B4 you Start...such as A Battery Powered Hand Drill, Extra 1.5" slender Stainless Steel Screws, the Proper Silicone Sealer and Gun and a Roll of Nashua Aluminum HVAC Duct Tape for permanent sealing and closing up the seams on those Opened Ducts. And of course... the EXACT Make & Model BDA to perfectly replace the original OEM Unit. Stick to buying an OEM Delphi or ACDelco Replacement Component, if possible.

(3) Plan for a Full Day-Long Time Line so you won't feel compelled to rush. As you enter and leave the Work Field... Look everything over very carefully from Three Different View Angles because you just might discover in that momentary pause and observation that a change in your approaches can wind up saving you hours of labor in the long run.

(4)The more it hurts to do this work... the harder it will be to concentrate on the job.... so do not be ashamed to use some Medium Sized Pillows (...wrapped and taped up inside of Garbage Bags to keep them from getting ruined) to lay down and/or kneel upon and get as comfortable as possible when leaning over the seat and the door Rocker Panels to get under the damned Dashboard on the Passenger side of the Vehicle.

(5) Refer to as many Youtube Videos as you can get your hands on to bolster your knowledge ...and your courage. And I repeat this idea... Taking frequent "Breaks" will help you to avoid getting a "Case of The Breaks" during the struggle.

(6) If you are able... Take some pics and/or videos of your work and Post them back here...and you will become "The Hero of Your Own Story" for others with similar problems to follow... and The Very Best of Luck to you... :>)
 
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LVJJJ

Active Member
#5
Great advice, thanks. Being rather experienced at fixing things, I know it ain't comfortable getting under there. I'm an upper level shade tree-hammer mechanic (not real good, but not real bad either) so I've done a lot of work like this over the past 7 decades. It has occurred to me, what does this blend door do? If I use the redneck solution and just unplug it, do I lose A/C? Sounds like it blends heat to the A/C so the A/C won't freeze you out.
 

MRRSM

Lifetime VIP Supporter
#6
Please don't be offended...my explanations are invariably as complete as I can make them ...and never meant to be insulting or given with any pejorative intent. To answer your last question... During the designs of the post-1980s Vehicles... some systems actually used the Air Conditioning and Heating Exchangers at the same time... right along with a necessary percentage of the intake of Fresh, Ambient Air to literally "blend" the conducted air coming from all three sources. It was done this way in order to Moderate and Cool down any excessively Hot or Frigid Cold Air Streams into one flow that would become less stridently "intemperate".

The very latest designs ...even in " Pick Up Trucks" ...includes isolated "Comfort Zones" using this method with PCM HVAC Controlled Modules watching things to "fine tune" the environments inside of the Front and Rear Passenger Compartments. These Blend Doors access this mixture of Hot, Cold and Fresh Air Streams and once mixed, they guide the bulk of it through the Under Dash Ducting ...to Keep Everyone Happy and not "Venting" about their discomfort.

If the "Blend Door(s)" were positioned to direct the air out of the Window Vents when the A/C is on... it would cause the outside of the Wind Screen to cool down so much that condensation might collect on contact and make it necessary to run the Wipers to clear the stuff away. Likewise...if you required Heat and the "Blend Doors" were only positioned to drive Warm Air towards the Lower Cabin... until the interior warmed up enough... Ice could form and remain on the Windshield and not rapidly Defrost. It would all depend upon what their positions were in when they cannot be controlled with the HVAC Panel Controls and working BDAs.
 
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LVJJJ

Active Member
#7
not offended at all, really appreciate the advice, some new, some reminding me how awful it is under dash. I'll have to see whether I've got heating, cooling, defrosting, etc. next time I drive it. Wife says just put up with the clicking. Just really appreciate knowing what the problem is.
 

MRRSM

Lifetime VIP Supporter
#8
I'm not sure whether or not the Blend Door Actuator for your Older Model 94' GM K1500 has been "Grandfathered In" right along with the latest BDAs designed for Late Model GM Trucks... but apparently, with the addition of a "Green Gear" POT Resistance Adjustment in the Newer BDAs ... it is entirely possible to get one ROTS (Right Off The Shelf)... and STILL winds up with having Blend Door Actuator "Out of Sync" Problems. So observing how this Video Original Poster works away while performing a Beautiful Tear Down, Adjustment and Re-Assembly of the Old & New BDAs is well worth watching:

 
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LVJJJ

Active Member
#9
"Fixed it" Saw a redneck solution on YouTube, disconnected the power to the door way up under the dash with a long screwdriver. Doesn't seem to have affected anything, heat works, defroster works, a/c works, vent works
 

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