Leprechaun in Suburban AC unit

Sounds like a leprechaun with a hammer has crawled up into the blower/air handling unit on my ?94 Suburban C1500 2WD. When the A/C is turned on, there is a bang, bang, bang that comes from the area near the blower motor. Need help getting the cover off to see if I can locate that little sucker and take the hammer away. Switching between regular and max A/C makes him go away for a little while, but he keeps coming back. Any help would be appreciated. Thanks, Rainman

Reply to
rainman14624
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"rainman14624" wrote: > Sounds like a leprechaun with a hammer has crawled up into the > blower/air handling unit on my '94 Suburban C1500 2WD. When > the A/C is turned on, there is a bang, bang, bang that comes > from the area near the blower motor. Need help getting the > cover off to see if I can locate that little sucker and take > the hammer away. Switching between regular and max A/C makes > him go away for a little while, but he keeps coming back. Any > help would be appreciated. > Thanks, > Rainman

Check charge level first as it may be over charged and you have a "slug" of freon or oil "banging in there as it heats and expands.

Reply to
SnoMan

this is a JOKE, right ?

please tell me you aren't serious about this

Reply to
TranSurgeon

It's no joke. My '93 3/4 ton Chevy diesel p.u. does the same thing. It's the recirc. door actuator and I'm going to tackle mine soon. When the key is turned on the actuator is commanded to open, (if you've don't have the "max" button pushed), for 10 seconds. The acutator is faulty, it's running to the end of it's travel and the nut on the wormgear is popping of the end of the the worm. The door the actuator controls is spring loaded, so it sits there and pops like that for about 8 or 10 seconds. There's likely a clip or snapring on the end of the wormshaft that's come off. You need to replace the actuator, and it looks like a pretty aggravating job in my '93. Don't know about your Suburban. I'm an airline electrician and I'll bet I've seen a couple hundred door actuators on Boeing and Douglas do this. Same design. The other actuators in the a/c in my truck have a position output to the a/c control. It knows where they're at, so they don't overrun. If you change it out soon, I'd like to know how bad of a job it was, if you don't mind.

Garrett Fulton

Reply to
Garrett Fulton

no, I meant the part about 'a slug of Freon or oil'

Reply to
TranSurgeon

Sorry about that. I misread the post.

Garrett

Reply to
Garrett Fulton

I have actually seen it happen in overcharged systems where the freon does not expand properly becuase evaperator pressures are too high and the liquid boils off in "slugs" that can bang around as the gas expands in evaporator and can cause quite a fuss. It is kinda rare but I have seen it happens.

Reply to
SnoMan

and just HOW does this 'slug' get past the orifice tube ?

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Reply to
TranSurgeon

That would actually be classified as a gremlin. Unless he's leaving breakfast cereal in the vents.

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Reply to
Stan

Actually quite easily, if the pressure in evaporator is high enough, it will just squirt through office without really expanding and pool on the otherside of orfice and then the pool/slug will move and bang around as gas try to axpand behind and around it as pressure drops and from the pool starting to boil itself. It is all about pressure and tempature and charge level. While evaporator generally do not have liquid in them, they can on occaision for reasons above. There is also a remote possibilty that he could have some moisture in freon that is freezing up and breaking loose and causing the noise too.

Reply to
SnoMan

but.......you just said that the pressure in the evap was too high for it to expand

if that is true, it would just lie there as liquid

you can't have it both ways...........either it stays liquid or it expands as it comes thru the orifice tube

Reply to
TranSurgeon

Not so, it the temp and pressure is right t will just squirt thru as a liquid and flask boil when it reaches a spot in evaporator warm enough to boil it at its current temp and sometimes "cluck" and "pop" while doing it. The temp has to be considerably above its boil point at a give pressure for it to "flash" to vapor the instant it leaves the orfice. It can happen and I have seen it! On why to confirm this problem is to watch the gauges (high and low) while it is doing it. if low pressure jumps around while banging, you have a "slug" problem cause by a overcharge, weak compressor or a bad orfice valve. (slight chance of ice/moisture too)

Reply to
SnoMan

Garrett: Sorry for the late reply. Been on a fishing trip in south Florida. I haven?t had a chance to fool with the Suburban?s leprechaun, but I suspected something like your diagnosis. I pulled the bottom plastic panel off the air handling unit and couldn?t see any access. Do you think I can get to it through the glove box? Never tackled anything like this before. Thanks, David

Reply to
rainman14624

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Wish I could help, David. I haven't replaced my actuator yet but the cursory look I gave to the job seemed to indicate quite a bit of dismantling of the underdash area. Good luck.

Garrett

Reply to
gfulton

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