NRAROX

My AC fan is running like crazy but not moving any air. I’m replacing the air conditioning hoses and the system is fully discharged so now is the time to figure out what to do. I’m wondering if the evaporator has stuff blocking it. And if I must remove the evaporator, I’m wondering what the procedure is. Details follow. Where should I go from here? BTW, happy Independence Day.

Blockage Assessment- I tried to snake an endoscope down into the blower air intake by the wipers to check for blockage without success. Two problems: 1. I really have no idea where the inlet is (only approximately) and there are a lot of dead ends; and 2. My endoscope has a very poor light so it must be very close to any object to work. First question, since the fan is on recirculate during AC use, can there really be any blockage that is relevant?

Air Selector Operation- The air selector doors were opening properly when I replaced the actuator on the firewall side of the air selector duct (heater core box); although I have not pulled the panels to verify.

Evaporator Housing (Partial Removal)- I’ve read most of the threads on the evaporator removal but cannot find the details I seek. Can I remove just the right half of the evaporator/blower assembly housing? If so, how many bolts/screws/nuts are there and where are they located? Another Forum posters described four bolts holding the two parts together. I can only find three. He then describes removing two more bolts that hold the right side of the housing to the firewall; one from at the top and the other at the bottom (accessible from under the car). (My car has nuts on studs at the top; I presume the bottom is the same.) He then describes how his housing got stuck and how he had to loosen the Air Selector (aka heater core housing) inside the cabin. What is up with that?

Evaporator/Blower Assembly Removal- In reviewing the AIM it appears that the evaporator/blower assembly was installed as a single unit, with three nuts (two at the top and one on the bottom (toward the engine); that seems odd as the lower fender side would have no fastener. That said, am I better off removing the entire assembly? If so, how many fasteners are there?

Valve Removal– Regardless of how I do the above, I’m thinking of removing some of the attached valves and fittings to clean them up. Do you see any issues with that? Will I need to replace some o-rings or other seals? For example, there are a couple seals on the compressor fitting/muffler assembly; must I replace those seals?

Thoughts?

This photo from another member does a good job of isolating the right side of the Blower/Evaporator Housing (and showing the usual Corvette tight spacing).

DUB

You are not going to get the assembly out very easily as a unit ...with the engine in the car.

Removing the white half in the photo you posted will work but getting to the screws that hold those two halves together can be a challenge due to the brackets and A/C system parts may get in the way.

Just make sure that IF you remove a hose or line...tape it off IMMEDIATELY!

The other half that has the blower motor attached to it is being held in with nuts also due to threaded studs coming from the firewall. These can be fun to get to also.

YES...the heater box is holding this in place due to the two studs the top are on your heater box...and if I am not mistaken the inner lower bolt may need to be removed also.

I would check and see if coming off of you blower motor you have rubber hose that goes over to the evap box. I have removed that hose and used my borescope to go in and see what the front face of the evap core looks like. I know later year models have this hose but I cannot remember if a 68 does or not. To much to try to remember on the fly.

Getting ti apart is one thing...getting it all back together with the seals and such can be more of challenge....just saying.

DUB

NRAROX

Thanks, Dub. I will look for that hose, but cannot recall seeing one (from memory). To the point of taping off openings, are you concerned about something entering or just atmosphere (and H2O in that atmosphere)? The hose broke over 13 years ago so I'm sure the atmosphere in the system is the same as my garage. Yes, I've been warned I may run into some bad things.

NRAROX (Happy Independence Day)

NRAROX

Dub, my car has the tube to which you refer - I presume it is part of the water precipitate system. Are you suggesting I temporarily disconnect that tube from the evaporator housing and put my bore scope in that opening? (It seems pretty flexible despite its age so I guess there is little risk in damaging it in the process.) Is that where debris sometimes gather? That would mean the debris is carried past the fan by the fan itself and then pushed against the evaporator radiator. Correct? I've never had mine apart so I am flying blind.

Thanks.

NRAROX

DUB

YES...IF you are referring to the rubber hose that is attached to the side of your blower motor....that goes down to this plastic fitting that is attached to the side of the evaporator case hours...YES...that is the side of the evaporator core ITSELF that will get plugged up with leaves and crud due to the blower motor has allowed it to pass by it when it was running.

Keep in mind that form my experienced...I bend my borescope down and try to look at the bottom of the evaporator core itself adn see how much crud and filled up in the bottom due to the SHAPE of this housing. I have seen some over 30% covered with what I literally call compost due to it can be wet and you could grow tomatoes in it if you threw in some seeds.

As for why I mention masking of or REALLY sealing off any open areas on your A/C system is two fold. I do not want crap to get into the system...but more so. I do not want the system exposed to moisture if at all possible. I know the system will have a vacuum put on it to pull it out....but sealing these off can aid you in NOT having to replace parts due to NOT sealing them off.

I would say that IF you get out the evaporator core...I would have it checked and or replace it.. And IF you do plan on getting a new one..,,I would ALSO have it checked. I ASSUME nothing is as how it is supposed to be.. And that goes for new heater cores, radiators and condensers. Because you would be surprised on how many 'new' parts that when tested where leaking right out of the box.

DUB

NRAROX

Thanks again, Dub. Well put, especially your experience with 'new' parts. I will give the scope a shot.

It looks as though there are six bolts that hold the housing together: two at the top, two on the side, and two on the bottom. Inserted below are pictures of a 1969 housing from ebay; they say the same thing.



I could not find anything helpful in the service manual, other than this illustration of the air flow, showing the position of the evaporator and fan. (I believe this will show up as an attachment.)

From the Corvette Parts Book I found an illustration of the assembly from 1967. It shows three studs protruding from the firewall and a nut, likely attached from the cabin, at the 5 o'clock position. Does that reflect your experience?

NRAROX

Here is a larger version. I got that one too small.

DUB

The 1967 is COMPLETELY different and you cannot use that information from the illustration you posted.

What are your concerns at this point???

DUB

NRAROX

Thanks. That's helpful. At this point I am simply trying to anticipate the number of fasteners that will need to be removed on the engine side of the housing as well as their location. Also the number of fasteners attaching the housing to the firewall and their location. I overthink things but prefer to have a solid plan in my head before turning a wrench. After I scope the hole this may be a moot point. Hopefully that will be the case.

NRAROX

DUB

Understood. Will wait and see what you find out with your scope.

But you basically have it figured out. on how to get the one half off.

DUB

mrvette

Two things, once you get it cleaned out, get hold of that spring on the outside/cowl/fresh air intake door under the fender, and disable it, then seal the door shut with RTV, remove the door behind the pass side kick panel, and block the single control vacuum line that ran both of those doors.....this puts the a/c on constant recirc, and reduces the amount of crap that blocks the air flow....I did this some 20 years ago to my system in my '72 and I got air flow even better by replacing the C3 blower/fan/motor assy with one from a C4 and making a 3/4 inch spacer for it because larger fan/squirrel cage.....my hvac really blows now, freeze the keys in the ignition, and I"m in FLORIDA with humidity matching temps......
As you can see from my pix below, my car is totally modified, NOTHING stock from wheels through roof, and stem to stern...NOTHING.....

NRAROX

When I pulled the pipe, I saw this junk hanging from the pipe inlet.



I then hooked a rubber gas line drain hose to my shop vac.

When I was done, I saw this:



What the heck is that? I then reduced the hose with the housing from a plastic mechanical pencil. I got this:


Yup, 2 Tablespoons of some kind of seed. I'm betting a mouse made a nest in there at one time or another. How would that much seed end up in the same place.

After sucking that out, all I could get was this:



The tube bends going into the housing and my scope is too long to make the turn. That tiny light brown thing at the end is either a gummed up evaporator or more muck. While I was jiggling it, more seeds fell into the opening. I'm thinking I have to pull the thing apart. Your thoughts?

Mrvette, while I don't like to modify the car, I think you're right. When the controller is set to 'Vent' the air is hotter than blazes anyway.

NRAROX

chevymans 77

Pull the blower motor and put your scope in there, at the bottom of the case you'll be able to see the coil,
This was mine from when I pulled it to clean it,

chevymans 77

You may have some luck with a small vacuum hose through the blower opening once the blower is removed. Then spray some coil cleaner in there with a flexible sprayer wand, not the best option but may help with air flow and prevent the need to remove the coil.

Neal

NRAROX

Good idea. Wow! That is a ton of stuff.

chevymans 77

A couple things you can check is that the blower is getting 12 volts or higher when on high, voltage is critical to the blower. When checking the voltage make sure to use the ground wire that the blower is using. There are also many threads about installing a blower motor from a newer vette as they used a larger blower and they move a good bit more air. Its a modification that is not permanent, you need to add a spacer to space the motor out around 3/4" as the blower wheel is longer.

Getting the coil clean is probably the most important thing you can do to get more air flow.

Neal

chevymans 77

I had the motor out when I pulled mine so it wasn't difficult but with the motor in I'm not sure I would have been able to get it out.

chevymans 77

I'm not sure if the 68 had the little grills on each end of the wiper gutter area but they are critical to keeping the debris out of the air inlet to the blower.

Neal

NRAROX

I tried adding a pigtail loop to increase the ground strength; no change. I can't remember testing the voltage, but I must have; my memory is not what it once was. I plan to do the blower upgrade, but first I need a working system. For now, I think I can get to the blower for inspection. With the blown hose from 13 years ago I can only wonder what I will have to replace.

DUB

If you have had a blown hose for your AC system and it happened 13 years ago.

I would suggest a complete replacement of the evap core and condenser...and any other part you feel comfortable in replacing. The reason I say this is my A/C guy says that when moisture enters the system it actually starts to corrode the inside of the condenser and evap core.

So when I get one in my shop like this I do not try to save anything and then have to get back into it time and time again. New parts where ever possible and then I have the compressor sent out for rebuilding. I may do VIR eliminator kit. In my opinion there are times when trying to save parts is OK...but then there are times to spend the money.

Granted... I do not have a crystal ball...so I cannot see into the future...but I rather put new parts on that make sense instead of having to deal with problem due to trying to save a buck.

DUB