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bigcoaxum on Tue May 06, 2008 11:21 AM User is offline

Year: 1973
Refrigerant Type: R134A

Ok, this might take a minute to explain but I hope someone can help. My problem all started when I noticed I had a very poor air flow coming out of my vents. I took my car to an A/C mechanic and he told me I had anywhere from a 500-1500 dollar problem but could not give me an exact amount to fix it. Any way, what I decided to do was to fix it myself. I have taken the dash board completely apart and found out why my circulation was so poor. The box (Black box) that all of my air vent ducts connect to was destroyed. It was cracked, had been taped together but not no able to be used. the ducts had all come apart. Since I have the dash apart and I'm able to see exactly whats going on, I want to try to fix all the problem while i can. The first thing i would like to know is where can i find some duct tubes to replace the old worn out duct. While under the dash, I started my car and played with the temperature control switch to change from defrost to ac to vent to heater etc. Just to make sure everything is ok, I would like to check to see if all of my vacuum lines are connected the proper way but i'm not sure how this is suppose to be done. I noticed that when i switch the control to AC, the door all the way to the right below the passenger side of the dash opens up and lets the air flow in. I'm not sure what doors are suppose to open when i switch the control to different levels. Can anyone help? Also, my switch only works on High or Low but not the two middle stages. I have a four cycle switch. the switch is brand new, not rebuilt or refurbish. What could be causing this to happen? Under the hood, My freon is freezing up on the line that runs to the back of the compressor and on the line that goes into the evaporator core. I was told that the evaporator is probably stopped up and thats what's causing this to happen. If anyone has a diagram of how the dash ducts should be installed and any information on how to check the vacuum lines to make sure the doors are opening and closing properly that would help alot. I'm also looking to install a new blower motor but i'm not sure where its located. As you can see i have alot going on but withing a few weeks I should have it straightened out with a little help. Any feedback would be helpful. Also, any webistes or links for installation would be helpful too.

mk378 on Tue May 06, 2008 11:59 AM User is offline

That frost is a good sign, it means the evaporator is getting plenty cold. If you can just get the air to flow thru it.

The intermediate speeds of the fan are controlled by a resistor unit usually located near the fan motor.

bigcoaxum on Tue May 06, 2008 1:38 PM User is offline

So I need to try to get the air flowing through my evaporator? Since the tubes are freezing does this mean my evaportator is not bad?

Cussboy on Tue May 06, 2008 4:02 PM User is offline

That's what it sounds like to me, that the evap is OK. The constant air flow over it will prevent frost.

bigcoaxum on Wed May 07, 2008 8:04 AM User is offline

so what would be my next step to try to get the air to flow throw the evaporator? Should I try a new expansion valve?

Edited: Wed May 07, 2008 at 8:05 AM by bigcoaxum

oznznut on Wed May 07, 2008 8:52 AM User is offline


Had a similar problem with my 1967 Impala SS. First off, a new txv will do nothing for air flow. It only meters refrigerant to the evap. What you need to do is clean the evaporator. Not a bad job. You can do it yourself. Don't have to pay a shop.
1) remove the refrigerant lines into and out of the VIR. Or course the refrigerant has to be removed. Im pretty sure you have a VIR, if not, remove the inlet to the txv, poa inlet, and oil return line to poa.

2) Remove the screws holding the engine side of the evap "suitcase". 6-7 if I remember.

3) Remove suitcase/evap as a unit. If you have a small block, it will almost come out by itself. I have a big block, and even that was easy. Don't have to unhook exhaust or anything else.

4) Clean the evap and inside of the suitcase. Mine was caked with years of gunk. Almost looked like a blanket over the evap fins. You'll find the suitcase fully of leaves, trash, small Japanese cars, etc.

5) When all is spotless, put it back together. Good time to check the evap fins. Straighten them with a small screwdriver or a fin comb. BE CAREFUL.

My airflow probably tripled or more.

Good luck


oznznut on Wed May 07, 2008 9:05 AM User is offline


Part 2.

Vent tubes can be sourced from nearly impala supplier. Classic industries, year one, classic muscle etc.
On my impala. have to remove bumper, hood, right fender to remove blower. Cross fingers you don't have to.
Might try junkyarding to find under dash air box. Thats where I got mine.

Now, for any a/c stuff, get it from ac kits. They run this forum and have good stuff / good prices.


bigcoaxum on Wed May 07, 2008 11:19 AM User is offline

Thanks alot. I'll try all of that and hope it works. I'm sure it will. I'll be sure to post and let you know the outcome.

oznznut on Wed May 07, 2008 11:39 AM User is offline


Part 3.

I would go to any of the impala suppliers and purchase the FACTORY service manual. NOT a chiltons or haynes. This will show all the controls, doors, sensors, etc. Explains how/why the system works---and how its put together. I have 67,70,71 but I am sure your system is just enough different for these books to be worthless to you.

Again--good luck. You should almost be able to hang meat in there when you get it right.


oznznut on Wed May 07, 2008 11:40 AM User is offline

PS Go back to R12. Your VIR or POA is set for it, it cools better, and is not really that much more than 134a.

bigcoaxum on Tue March 29, 2011 8:57 AM User is offline

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