AC/Heater help

[jteck10]

sorry if this is posted in the wrong spot.

I recently had my belt rip apart on me in my 1990 k5 Blazer
when i went to put a new one in, i noticed the connector on top of the AC compressor was about to fall off
(before the belt ripped, my AC and heater both worked fine)
so as i pull the connector off to clean and put back on, the two tabs on the AC compressor completely break off

i took the truck to a shop and had them depressurize/repressurize the system, i replaced the AC compressor and put the connector back on the new compressor
now when i try to turn on my air, i get a faint hissing noise from each setting (defrost, etc.) that slowly fades as i change them
no AC, no heater

the shop told me i had 1.1lbs in the system, and they replaced 1.1 lbs

im going to start with fuses, but anything else that might be preventing my heater/AC from working now?
vacuum leak somewhere? blower motor for the heater out?

any help is appreciated

 

[Wes Harden]

So the positions, defrost, heat, vent, ac, each position changes doors to open and close various paths in the plenum. This is done with vacuum. The hissing maybe vacuum leaking.
The blower should run with the fan switch. When the vacuum system fails the the doors default to defrost, put the blower on high and check for air at the defrost vents, if you have a strong flow of air from defrost vents in any position, this indicates a vacuum problem.
There should be a black hard plastic vacuum line form intake manifold to a vacuum reservoir, looks like a black plastic ball bolted to the firewall, normally near blower motor. From reservoir it should go through the firewall, somewhere near the a/c housing. this line get brittle and fragile with age, is very easy to break. My 1st goto is this vacuum line, when doors aren't working.
If no air from blower at all, is probably electrical. The may have blown fuse when the clutch coil failed. Check all your fuses. There will be a resistor block and a high blower relay, both on the a/c plenum under the hood.
1.1 pd of gas is not enough, what gas did they charge the system with ? R134a ? R12?

these two attachments aren't 1990 but are similar to what your system is.

Welcome to CK5
If you can't see the attachments let me know

 

[jteck10]

So the positions, defrost, heat, vent, ac, each position changes doors to open and close various paths in the plenum. This is done with vacuum. The hissing maybe vacuum leaking.
The blower should run with the fan switch. When the vacuum system fails the the doors default to defrost, put the blower on high and check for air at the defrost vents, if you have a strong flow of air from defrost vents in any position, this indicates a vacuum problem.
There should be a black hard plastic vacuum line form intake manifold to a vacuum reservoir, looks like a black plastic ball bolted to the firewall, normally near blower motor. From reservoir it should go through the firewall, somewhere near the a/c housing. this line get brittle and fragile with age, is very easy to break. My 1st goto is this vacuum line, when doors aren't working.
If no air from blower at all, is probably electrical. The may have blown when the clutch coil failed. Check all your fuses. There will be a resistor block and a high blower relay, both on the a/c plenum under the hood.
1.1 pd of gas is not enough, what gas did they charge the system with ? R134a ? R12?

these two attachments aren't 1990 but are similar to what your system is.

Welcome to CK5
If you can't see the attachments let me know

View attachment 400730

View attachment 400733

Thanks for the welcome! Pumped to be in here more often. Couldn’t see the attachments, said I needed a premium account

When you say ‘blower should run with the fan switch’, you mean by the ac/heat controls on the dash right? They don’t currently. there is no air at the defrost when on high.

Ill check the vacuum line at firewall when I replace the fuses tomorrow. But I believe the issue to be electrical. Where is the high blower relay?

also, they charged with R134A. Anyway to find out how much is needed more than 1.1lbs? I couldn’t find anywhere

 

[Wes Harden]

There should be a sticker on the a/c plenum, or the radiator support, that list the a/c capacity for r12. When changing to r134a you need @ 80% of the r12 charge.
High blower relay will be under the hood passside near the blower motor. Do you have any fan speeds ?

 

[jteck10]

There should be a sticker on the a/c plenum, or the radiator support, that list the a/c capacity for r12. When changing to r134a you need @ 80% of the r12 charge.
High blower relay will be under the hood passside near the blower motor. Do you have any fan speeds ?

got it, I’ll have to check to see if there’s a sticker anywhere in the morning for the lbs. in looking around online I’m thinking maybe 3lbs?
Also, not sure if it’s worth mentioning, I didn’t add anymore oil to the compressor than the 3oz that it came prefilled with. Not sure if I need to add more or where or what type

I have fan speeds from low to high, about 4 intervals I believe

 

[frankin5]

I did find a listing in napa for a 1985 chevy truck with R4 compressor listing it at 44 OZ of R12 and 8 OZ oil. That would be about 39.6 OZ of R134a, roughly equivilent to 2.475 lbs if my math is correct.

High blower relay will be under the hood passside near the blower motor. Do you have any fan speeds ?

located on right side of AC clam shell,

 

[jteck10]

I did find a listing in napa for a 1985 chevy truck with R4 compressor listing it at 44 OZ of R12 and 8 OZ oil. That would be about 39.6 OZ of R134a, roughly equivilent to 2.475 lbs if my math is correct.


located on right side of AC clam shell,

ah, got it. So no more oil but add more lbs to get from 1.1 to 2.5lbs

 

[frankin5]

Too much oil is not good. Needs more gas.

 

[jteck10]

There should be a sticker on the a/c plenum, or the radiator support, that list the a/c capacity for r12. When changing to r134a you need @ 80% of the r12 charge.
High blower relay will be under the hood passside near the blower motor. Do you have any fan speeds ?

Still trying to get this sorted out.

No sticker anywhere on radiator or fan housing for system pressure amount

I called the same shop that depressurized and repressurized the system for an estimate to get from 1.1lbs to 2.5lbs. I’m still not sure if that’s the right pressure, so I’m taking @frankin5 advice from below. Probably do this Monday. I noticed my system says it’s r12 and I think they charged it with r134a. How do I know if my system was converted previously? I have a picture of the nozzle if that helps. If it wasn’t converted, what now???

I ordered a new blower motor resistor, relay, and bought fuses to do all at once as well. I figure if repressurizing doesn’t work, those are worth a shot next.

There’s a connector I can’t find circled in one of the photos below. Anyone know what it is? Resistor connector?

I think I’m on the right track to get this figured out?

 

[jteck10]

 

[Wes Harden]

The fan should run wether you have a pressurized system or not.
So you do have an electrical issue.

Yes it wouldn't surprise me if your truck was converted. Yes that r134a connector. Got very hard an expensive to purchase r12.

 

[Wes Harden]

The sticker in the middle photo should have capacity near where it says r12

 

[jteck10]

The fan should run wether you have a pressurized system or not.
So you do have an electrical issue.

Yes it wouldn't surprise me if your truck was converted. Yes that r134a connector. Got very hard an expensive to purchase r12.

Got it, hope the resistor, relay, and fuses do the trick. Any idea what that connector is?

I’ll try and go look at the sticker better to get the capacity. Looks like it wore off

On another note, Became a premium member! Whoo

 

[Wes Harden]

No real clue about connector, It has a nice factory cap on it so it ma be an option you don't have. The EST( Electric Spark Timing ) has a connector that is similar, but I remember on the left and having brown colored wiring.
Congrats on Premium I think you will enjoy it.

 

[jteck10]

I’ll say again, use superheat/subcooling to charge.
I can’t see the pics as I let my membership lapse ( too much pay a shop to do it posts)

the age and abuse with prior owners that these trucks have you’ll be lucky to have legible nomenclature.

I’ve never heard of that. Is superheat/subcooling something the shop can take care of? Or easier to diy?

 

[Wes Harden]

Yes this the best way, is kinda technical which is why, capacity is given. Having a capacity gets you in the ball park.