How To Clean HVAC System

[cc333]

I don't know if this is the proper place to post this, but I'm curious about something.

Everything seems to work more or less fine (all actuators seem to work, blower works at all speeds, A/C blows relatively cold (could be better I think, but that's a different topic), all controls seem to work), but it seems like the volume of air with the blower on full is somewhat lacking.

Why?

Is it dirty? If so, is it possible to clean it without opening everything up?

I was thinking I could just shove the hose of my shop vac in the ducts for the panel vents and see what happens, but maybe that's a bad idea?

c

 

[454cid]

I don't know if this is the proper place to post this, but I'm curious about something.

Everything seems to work more or less fine (all actuators seem to work, blower works at all speeds, A/C blows relatively cold (could be better I think, but that's a different topic)), but it seems like the volume of air with the blower on full is somewhat lacking.

Why?

Is it dirty? If so, is it possible to clean it without opening everything up?

c

I'd assume your heater core and/or AC evaporator are dirty. The heater core is easy to get to on our trucks. After pulling the 6 or 7 screws (there is one hidden in the back next to the firewall) the heater core will free except the the heater hoses. I've never tried to drop the heater core without first having the hoses disconnected, so I don't know what kind of movement there is there. If you are able to move it, or just remove it, you'll have room to shove a hose up there and spray the evaporator.....AFTER, you've pulled the blower moter out on the other side. I think I sprayed the evaporator from both directions. As you may have surmised by now, I don't have carpet in my truck. However, I think heavy plastic or a tarp could be spread well enough, and draped out the door to get rid of the water. I may have used a shop vac to get the last of the water out of where the blower motor goes.

Ok, here's the answer you actually asked for. Yes, there is a way to clean evaporators with everything assembled. You spray a coil cleaner up the drain tube, and follow a Youtube video and/or the instructions on the can. However, I'm not sure that's going to be as effective as it could be on our trucks. Our trucks have a higher chance of collecting larger pieces of stuff than many vehicles because we don't have cabin filters. If there is grass, leaves, dog hair, Taco Bell bags, I don't think you're going to get that with coil cleaner very well. It's more for molds/smells than chunks of debris.

 

[cc333]

Thank you for the timely reply!

I see. The air smells OK, so mold isn't a problem, for what it's worth.

This will be a long-term project I think, as I'm not eager to mess with the heater core until I have lots of time to do it carefully and right (I've never worked on anything related to heater cores before, which is connected to the cooling system, if I'm not mistaken).

In the meantime, can I try pulling the blower motor (which I should be able to handle) and blowing/vacuuming stuff from there, maybe?

It won't do a complete job, but better than nothing?

c

 

[454cid]

It wouldn't hurt. You want to vacuum not blow, as the blowers already been doing that. That would also give you a chance to inspect the blower.

 

[someotherguy]

Yep, vacuum the junk out of there, then spray some evaporator core cleaner in there too, because guaranteed what's really clogging up the fins is caked-on dirt. All the air in the system must pass through the evaporator core, regardless of any settings; it's directly in the path of the air from the blower motor.

It's a little tricky and you'll need the smallest possible vacuum nozzle, and if it's either short, or flexible somehow, that will help. The HVAC box necks down between the blower motor housing and the evaporator core.

Leaves, pine needles, and debris, absolutely..

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But the caked-on dirt, mud, is the real airflow killer.

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Those pictures are from where I took a box out of the truck (requires pulling the dash) and took it all the way apart. You can get a lot done without pulling the dash or box. But, you'll see when you get the blower motor out, that access is limited.

Section with blower motor housing on the left; you can see the necked-down area where the air travels through to the evaporator core, and just how crudded-up they can get.

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I was gonna say, no sense pulling the heater core down to clean it as they don't really get dirty. However, if you are going to clean the evaporator core in place like @454cid is suggesting, getting the heater core down will allow you access to spray water against the backside of the evaporator, which you'll need to rinse the cleaner and crud out. You'll need to adjust the temperature control door above the heater core (turn the controls to full hot - don't try to manually move the door) so that it moves up out of your way. Be careful not to bump the door as you can break it. This picture also shows the locations of the screws that hold the heater core cover on.

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Richard

 

[jd33173]

May also want to check your door is closing when you have it on max cold- believe this is door in the blower compartment. Makes a big difference

 

[cc333]

OK, I'm glad I asked!

So, where, exactly is the heater core access door located? I'm guessing it's in the engine compartment to the left of the engine, somewhere on the firewall. Please forgive my ignorance, as I've never paid any attention to it, so I don't know exactly what it looks like in context.

This is a like-long California truck whose interior is in overall excellent condition for its age, including the original dash, the core of which is in almost flawless condition (there is one crack and blown out bolt hole on the bottom plastic, sort of under and to the right of the tape deck hole, but it doesn't appear to serve any structural purpose, thankfully), so I REALLY don't want to pull it if I don't have to!

c

 

[someotherguy]

Passenger side of the interior, under the dash. Be careful with it as it's easy to break it during removal. The foil tape you can see in this pic is my hack-y patch job of repairing one that a previous owner preemptively broke for me..

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The picture I included showing the screw locations, note that 1 of them is between the HVAC box and the firewall and can be tricky to get to (and easy to forget.) Securely taping the socket to the extension is a good idea so that you don't lose it due to it getting grabbed between the firewall insulation pad and the HVAC box and staying behind when you go to remove the tool.

Once the cover is off, the heater core will be exposed. It helps if you've already got the hoses disconnected at the firewall under the hood, then you just have 1 screw on a little bracket at the upper tank end of the core and you can remove it.

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Strongly recommend you go to the Engines section of this forum and look at the top of the post listing for the service manual downloads. They're free. Grab the manuals for your year model as they are immensely helpful and will answer many of the questions you've got. They obviously don't have all the "tricks" but the basic location of things and disassembly/assembly is covered pretty thoroughly.

Richard