A/C Help - 1989 GMC Sierra 1500

[Rtlane]

I just purchased a 1989 GMC Sierra 1500. I'm wanting to try and fix the AC myself to learn and also because the closest AC shop is over an hour from here. It is currently an r12 system, but with the price of r12 I'm thinking I should go ahead and convert to r134a.

So far I've bought manifold gauges and a vacuum. When I first got the truck, I pushed one of the valves and heard pressure in it. I just did it for a second because I know you're not supposed to. I tried to connect the gauges, but when I got them in the mail, I realized I'm missing an adapter for the high side of the gauges. I then pushed one of the valves in again and heard no pressure coming out of it. So it must not have had much left in it.
I did jump the low pressure switch for a few seconds and the compressor engages and has no noises, so I'm hoping it is good.

I'm going to pick up a retrofit kit so I can connect my gauges. Should I see if it holds a vacuum at that point (probably not because it's now empty and it had to go somewhere)? Or should I go ahead and flush the system, change the o-rings, accumulator and orifice tube, see if it holds a vacuum, then refill with refrigerant and ester oil? If so, is that all I need to change to convert to r134a? Doing research, some say I need to change condenser, get new high and lower pressure switches and get barrier type hoses, but others are saying I don't need to do that?

Any help would be greatly appreciated.

 

[PlayingWithTBI]

You can do what you outlined and probably be fine. Make sure you flush it well. I changed my condenser to this parallel flow one on my 88.
www.amazon.com/Spectra-Premium-7-4168-Condenser-Chevrolet/dp/B000CKOW02/ref=sr_1_1?dchild=1&keywords=7-4168+condenser&qid=1630688099&s=automotive&sr=1-1

These earlier trucks which don't have the "Max" A/C button work differently. To switch to "Max" your temp selector needs to be on its coldest setting and the fan has to be on medium or high. Then, it will open the fresh air/recirculate blend door after 30 seconds.

The OE 1 wire "High Pressure" switch on the back of the R4 compressor closes that blend door, when it sees high pressure to allow more hot air through the evaporator, hopefully to lower the pressure. THERE IS NO HIGH PRESSURE SHUTOFF SAFETY! I took this switch which closes at 200 PSI and opens at 430 PSI. I wired it in series with the low pressure cycling switch. Now I have a working high pressure safety switch. Before I did this, I had a brand new compressor blow that switch out the back of the compressor - sounded like a shotgun going off! When you shut off the hot engine, and A/C running, come back shortly after and start it back up, it'll build super high pressures for a while until the system equalizes. Without that safety switch you will blow seals or, like mine, the switch right out the back. It also tore part of the snap ring groove so, that compressor was junk. HTH

www.oreillyauto.com/detail/c/murray-climate-control/lighting---electrical/switches/body-switches/a-c-pressure-switch/5e3a6dc98ab1/murray-climate-control-2-terminal-pressure-switch/mry0/35961/v/a/3010/automotive-truck-1989-chevrolet-c1500-pickup-rwd?q=a%2Fc+pressure+switch&pos=0

 

[Frank Enstein]

Get a new receiver drier/accumulator any time the system is open to atmosphere.

Get the Blue Ford Taurus orifice tube per one of my customers in an A/C shop in Florida (this has worked well for me).

1989 FORD TAURUS Four Seasons 38621 Four Seasons Orifice Tubes | Summit Racing

Free Shipping - Four Seasons Orifice Tubes with qualifying orders of $109. Shop Air Conditioning Orifice Tubes at Summit Racing.

www.summitracing.com

Flush the system with A/C flush stuff or at least compressed air.

Button it up and pull vacuum on it and if it holds vacuum, Fill 'er up!

And what he said

 

[Rtlane]

You can do what you outlined and probably be fine. Make sure you flush it well. I changed my condenser to this parallel flow one on my 88.
www.amazon.com/Spectra-Premium-7-4168-Condenser-Chevrolet/dp/B000CKOW02/ref=sr_1_1?dchild=1&keywords=7-4168+condenser&qid=1630688099&s=automotive&sr=1-1

These earlier trucks which don't have the "Max" A/C button work differently. To switch to "Max" your temp selector needs to be on its coldest setting and the fan has to be on medium or high. Then, it will open the fresh air/recirculate blend door after 30 seconds.

The OE 1 wire "High Pressure" switch on the back of the R4 compressor closes that blend door, when it sees high pressure to allow more hot air through the evaporator, hopefully to lower the pressure. THERE IS NO HIGH PRESSURE SHUTOFF SAFETY! I took this switch which closes at 200 PSI and opens at 430 PSI. I wired it in series with the low pressure cycling switch. Now I have a working high pressure safety switch. Before I did this, I had a brand new compressor blow that switch out the back of the compressor - sounded like a shotgun going off! When you shut off the hot engine, and A/C running, come back shortly after and start it back up, it'll build super high pressures for a while until the system equalizes. Without that safety switch you will blow seals or, like mine, the switch right out the back. It also tore part of the snap ring groove so, that compressor was junk. HTH

www.oreillyauto.com/detail/c/murray-climate-control/lighting---electrical/switches/body-switches/a-c-pressure-switch/5e3a6dc98ab1/murray-climate-control-2-terminal-pressure-switch/mry0/35961/v/a/3010/automotive-truck-1989-chevrolet-c1500-pickup-rwd?q=a%2Fc+pressure+switch&pos=0

Thank you! I will order that high pressure switch. If i change it later, will it leak freon or is it sealed?

Can you link me to the proper low pressure switch for r134a as well? I took mine off today and i dont see an adjustment screw.

Do you think I should upgrade my condensor to the one you linked or do you think it will be ok?

Also, did you change your hoses to barrier type? I read that you should, but then also read that its not needed? Lol

Get a new receiver drier/accumulator any time the system is open to atmosphere.

Get the Blue Ford Taurus orifice tube per one of my customers in an A/C shop in Florida (this has worked well for me).

1989 FORD TAURUS Four Seasons 38621 Four Seasons Orifice Tubes | Summit Racing

Free Shipping - Four Seasons Orifice Tubes with qualifying orders of $109. Shop Air Conditioning Orifice Tubes at Summit Racing.

www.summitracing.com

Flush the system with A/C flush stuff or at least compressed air.

Button it up and pull vacuum on it and if it holds vacuum, Fill 'er up!

And what he said

I picked up that blue tube today, thank you!

 

[PlayingWithTBI]

If i change it later, will it leak freon or is it sealed?

You'll loose all of your charge.

Can you link me to the proper low pressure switch for r134a as well? I took mine off today and i dont see an adjustment screw.

The adjustment screw s/b between the terminals of the connector. I didn't change mine.

Do you think I should upgrade my condensor to the one you linked or do you think it will be ok?

It's more efficient.

Also, did you change your hoses to barrier type? I read that you should, but then also read that its not needed? Lol

Nope.

 

[Rtlane]

You'll loose all of your charge.


The adjustment screw s/b between the terminals of the connector. I didn't change mine.


It's more efficient.


Nope.

Thank you for the responses. Oreilly’s has the consdenser, hp and lp switch (for r134a) in stock, so im headed to pick them up now.

I looked on both sides of my lp switch and there is no screw. You said you didn’t change yours anyway, so maybe I can save $24. Lol

The condenser is the same part number as the one you referenced but just doesn’t say spectra, so I'm assuming it’s the same.
O’reilly Condenser

 

[Rtlane]

Ok, I changed the accumulator, all orings, condenser, orifice tube (blue one for ford taurus), hp and lp switches (wiring it like PlayingWithTBI).

I drained as much of the old oil from
compressor as I could.

I flushed the lines and evaporator.

I put 4oz of ester oil in compressor and 4 oz in the accumulator.

I vacuumed the system for an hour. After vacuuming, I discovered that the vacuum oil cap was broke, so hopefully that wont affect anything?

I put 32 oz of r134a in because r12 capacity was 2.5lb and i putin 80% of that.

The air from the vents feel really cold, but i dont have a thermometer to check. Plus it’s 70 degrees F outside.

The only issue I see, which may not be an issue, is the compressor cycles about every 5-10 seconds Sometimes longer. What could be the issue or is that even an issue? Probably need to test when its warmer. Hopefully I dont have a compressor issue. When the compressor is on, my low side pressure is around 30 and my high side is around 165. It’s around 70 degrees outside.

 

[df2x4]

The only issue I see, which may not be an issue, is the compressor cycles about every 5-10 seconds Sometimes longer.

In my experience this is usually a sign of the system being low on refrigerant.

 

[kenh]

I have a 90 C1500. It was also an R12 system. My compressor was froze so i bought a kit with new compressor, accumulator, oil and o-rings, etc. I wound up with 2LBS of 134 in my system and it blows cold as heck and the compressor does not cycle. Your high side pressure seems low to me as does the low side. I agree you need to add a little more 134. You changed the condenser which may be a larger capacity than the original. Let the system pressure tell you when you have enough refrigerant in the system.

EDIT: My system has 2 1/4 pounds of 134 in it. NOT 2 pounds as stated above.

Ken

 

[Rtlane]

PlayingWithTBI, since you used the same condenser, how much refrigerant did you refill your system with?