Sanity check for my AC diagnosis (1 Viewer)

[jbc28]

I just replaced my compressor and drier last week due to a faulty clutch and a cracked drier line. This is my 1st attempt at ac work. I followed jpooles thread on here. During install I pulled a vacuum for 2 hrs and then added 850 grams of freon. I didn't replace the expansion valve. I rolled the dice on that since I was running low on time to get it finished. It has worked great for a week. I was getting temps in the low 40's in 90F weather.

Today I cranked it up to let it cool off at work. When I came back out the compressor was short cycling on and off quickly. I also had bubbles in the site glass. This evening I put gauges on it and found the following

With compressor running the pressure is immediately above FSM specs on both high and low side. The high side is close to spec but quickly builds psi

Bubbles appear quickly in the sight glass

High side piping gets very hot very quickly. Low side piping starts off cool, but a few minutes into running it at 1500 rpm the low side starts to heat up. High side psi went above 400 in about 4 minutes. Low side psi was around 50.

It was still cooling well until the compressor started cycling

On shutdown bubbles in the sight glass dissappear and liquid is visible


After reviewing the FSM i think I have moisture in the system. If so, it must have entered when I was swapping cans of freon. I thought that I purged the supply and low side hoses correctly, but maybe not. I'm scratching my head on why it took a week and maybe 6 hrs of drive time to show up. Could the drier have been taking it out then finally get saturated?

If it is moisture should I have it professionally evacuated/recharged and replace the drier again or keep the 1 week old drier?

I appreciate all feedback. Thanks.

 

[jpoole]

Hate to hear you are having issues. I put that howto together using input from a number of folks on the forum but @flintknapper provided most of the info as I recall and is also good at diagnosis and troubleshooting AC systems so I'm pinging him here.

It seems like it would be hard to get problematic moisture levels into the system if you followed the fill process very closely, after a few hours of deep vacuum, so maybe there's something else going on that may end up being easier to resolve?

Hopefully you are on solid footing with the AC soon, it's too hot around here right now not to be!

 

[jbc28]

Hate to hear you are having issues. I put that howto together using input from a number of folks on the forum but @flintknapper provided most of the info as I recall and is also good at diagnosis and troubleshooting AC systems so I'm pinging him here.

It seems like it would be hard to get problematic moisture levels into the system if you followed the fill process very closely, after a few hours of deep vacuum, so maybe there's something else going on that may end up being easier to resolve?

Hopefully you are on solid footing with the AC soon, it's too hot around here right now not to be!

Thanks. I'm just not confident I got a good purge on the yellow line after swapping 2 cans. I do remember the high side psi being high when I was charging it through the low side, but as I got more freon in the system it dropped back close to spec.

 

[flintknapper]

Thanks. I'm just not confident I got a good purge on the yellow line after swapping 2 cans. I do remember the high side psi being high when I was charging it through the low side, but as I got more freon in the system it dropped back close to spec.

Doubtful your issue is moisture in the system from the procedure you described.

My best 'guess' not being able to actually see the gauge readings/function in real time is:

A restriction somewhere in the High Side. Usually this will occur at the TXV but can also be at the condenser.

The TXV is most suspect. It can become stuck Open/Closed or anywhere in between. Insufficient airflow across the condenser can also cause elevated high side readings....so check your fan clutch.

 

[jbc28]

Doubtful your issue is moisture in the system from the procedure you described.

My best 'guess' not being able to actually see the gauge readings/function in real time is:

A restriction somewhere in the High Side. Usually this will occur at the TXV but can also be at the condenser.

The TXV is most suspect. It can become stuck Open/Closed or anywhere in between. Insufficient airflow across the condenser can also cause elevated high side readings....so check your fan clutch.

Thanks. TXV = the expansion valve? Sorry I'm not up to date on abbreviations.

Fan clutch seems good. I also put a big shop fan in front of the grill with no change.

I forgot to mention that I'm not getting much condensate dripping. It does drip just very slowly and will continue for a while after shut down. I guess it's time to get into the evaporator.

 

[blinkerfluid]

I just replaced my compressor and drier last week due to a faulty clutch and a cracked drier line. This is my 1st attempt at ac work. I followed jpooles thread on here. During install I pulled a vacuum for 2 hrs and then added 850 grams of freon. I didn't replace the expansion valve. I rolled the dice on that since I was running low on time to get it finished. It has worked great for a week. I was getting temps in the low 40's in 90F weather.

Today I cranked it up to let it cool off at work. When I came back out the compressor was short cycling on and off quickly. I also had bubbles in the site glass. This evening I put gauges on it and found the following

With compressor running the pressure is immediately above FSM specs on both high and low side. The high side is close to spec but quickly builds psi

Bubbles appear quickly in the sight glass

High side piping gets very hot very quickly. Low side piping starts off cool, but a few minutes into running it at 1500 rpm the low side starts to heat up. High side psi went above 400 in about 4 minutes. Low side psi was around 50.

It was still cooling well until the compressor started cycling

On shutdown bubbles in the sight glass dissappear and liquid is visible


After reviewing the FSM i think I have moisture in the system. If so, it must have entered when I was swapping cans of freon. I thought that I purged the supply and low side hoses correctly, but maybe not. I'm scratching my head on why it took a week and maybe 6 hrs of drive time to show up. Could the drier have been taking it out then finally get saturated?

If it is moisture should I have it professionally evacuated/recharged and replace the drier again or keep the 1 week old drier?

I appreciate all feedback. Thanks.

Its cycling because high side pressure gets too high, that's usually a restriction, bad condenser or refrigerant overcharge

 

[blinkerfluid]

Thanks. TXV = the expansion valve? Sorry I'm not up to date on abbreviations.

Fan clutch seems good. I also put a big shop fan in front of the grill with no change.

I forgot to mention that I'm not getting much condensate dripping. It does drip just very slowly and will continue for a while after shut down. I guess it's time to get into the evaporator.

Yes, TXV is expansion valve, which could also be failing and acting as a restriction

 

[flintknapper]

Thanks. TXV = the expansion valve? Sorry I'm not up to date on abbreviations.

Fan clutch seems good. I also put a big shop fan in front of the grill with no change.

I forgot to mention that I'm not getting much condensate dripping. It does drip just very slowly and will continue for a while after shut down. I guess it's time to get into the evaporator.

Yes, sorry. TXV= Thermal Expansion Valve. It is attached to the evaporator.

Good that you went ahead and used a fan to increase airflow/cooling. Another way to check is to 'mist' the condenser/radiator with water and note if there is a significant change in manifold gauge pressure and lower vent temps. Since that did not have much effect...we can turn elsewhere for the issue.

It sounds to me like you have a 'partial' restriction. Since you started with an evacuated system and added a known amount of refrigerant (up to 1.98 pounds is fine), then we should not suspect an 'overcharge'.

Unfortunately....replacing the TXV requires evacuation of the system and removal of the Evaporator. It isn't as difficult job on an 80 series as it is with a 100 series and provides an opportunity to inspect and clean the Evaporator. It will be pretty dirty in most cases.

If you live in 'Bama' then you have high levels of humidity. On a typical Summer Day you should be seeing a good amount of condensation run off when your A/C system is working correctly. Since you are not....we know right there something is amiss.

 

[jpoole]

I'll throw out an additional question / idea. Did you flush the lines and clean the system before the last charge? Is it possible that there was leak repair added, debris from compressor failure or an open system in the past that could have resulted in things getting dirty?

Flintknapper and the other experts in this thread can weigh in on the likely need for cleaning if you have to split the system open again. Just pulling the Evap, replacing the TXV then resealing/recharging would obviously be easiest but if it seems possible that there is debris in the system then I wonder if you could possibly re-encounter issues unless you get the system cleaned up.

I'm also curious if you will want to change the dryer again or not but again assume that others on this thread will know what's best on that front.

 

[duece71]

Great thread, compiling parts myself for the AC system. Most likely an R12 to R134a conversion.

 

[jbc28]

I'll throw out an additional question / idea. Did you flush the lines and clean the system before the last charge? Is it possible that there was leak repair added, debris from compressor failure or an open system in the past that could have resulted in things getting dirty?

Flintknapper and the other experts in this thread can weigh in on the likely need for cleaning if you have to split the system open again. Just pulling the Evap, replacing the TXV then resealing/recharging would obviously be easiest but if it seems possible that there is debris in the system then I wonder if you could possibly re-encounter issues unless you get the system cleaned up.

I'm also curious if you will want to change the dryer again or not but again assume that others on this thread will know what's best on that front.

I didn't do a flush. My old compressor didn't fail internally. The clutch bearing was making noise, and I just replaced it with a new Denso. The drier line cracked when I was trying to bend it back into shape. I didn't drive it or try to run the compressor after that. System was working fine other than the bearing noise. I did notice that it had dye in the oil. I don't know the history. I just bought it back in Oct. Compressor and everything else appears to be the original parts.

I guess I will evac it and pull the expansion valve and give everything a good cleaning. I'm kicking myself for not doing it first. I have the valve. I was just running out of time the night before a group ride that I did.

 

[jbc28]

Yes, sorry. TXV= Thermal Expansion Valve. It is attached to the evaporator.

Good that you went ahead and used a fan to increase airflow/cooling. Another way to check is to 'mist' the condenser/radiator with water and note if there is a significant change in manifold gauge pressure and lower vent temps. Since that did not have much effect...we can turn elsewhere for the issue.

It sounds to me like you have a 'partial' restriction. Since you started with an evacuated system and added a known amount of refrigerant (up to 1.98 pounds is fine), then we should not suspect an 'overcharge'.

Unfortunately....replacing the TXV requires evacuation of the system and removal of the Evaporator. It isn't as difficult job on an 80 series as it is with a 100 series and provides an opportunity to inspect and clean the Evaporator. It will be pretty dirty in most cases.

If you live in 'Bama' then you have high levels of humidity. On a typical Summer Day you should be seeing a good amount of condensation run off when your A/C system is working correctly. Since you are not....we know right there something is amiss.

How does a condenser typically fail? I'm assuming plugging from debris. Learning as I go here. My compressor didn't fail internally. My clutch bearing was going bad. Hopefully its just the valve. I'm going to replace the expansion valve and try again.

 

[jpoole]

We all roll the dice sometimes and it could have worked out well for you. Removing/cleaning the evap is worth doing, esp. if you don't know the rigs history. I'll bet you find a decent layer of cruft on the evap.

 

[flintknapper]

How does a condenser typically fail? I'm assuming plugging from debris. Learning as I go here. My compressor didn't fail internally. My clutch bearing was going bad. Hopefully its just the valve. I'm going to replace the expansion valve and try again.

^^^^
Correct. Depending on Condenser construction....the 'tube' openings can be quite small and easily clogged. Stop leak products come to mind first.

 

[jbc28]

I'm back on the AC after weeks of distractions. I pulled the evaporator this evening and it was absolutely disgusting. At least half of the surface area was matted about 1/8" thick in dog hair, fuzz, and God knows what else. I've spent about an hour washing it and am still getting dirt out. I'm going use some AC condenser cleaner on it tomorrow. Also all of the foam gaskets are crumbling. So a trip to Lowes's is in order to pick up a few things. I'm going back with a new AC Delco expansion valve and new o-rings. Hopefully, this will fix it. In hindsight, I really should have bit the bullet and did this when I did the compressor. Live and learn.

 

[jbc28]

Yes, sorry. TXV= Thermal Expansion Valve. It is attached to the evaporator.

Good that you went ahead and used a fan to increase airflow/cooling. Another way to check is to 'mist' the condenser/radiator with water and note if there is a significant change in manifold gauge pressure and lower vent temps. Since that did not have much effect...we can turn elsewhere for the issue.

It sounds to me like you have a 'partial' restriction. Since you started with an evacuated system and added a known amount of refrigerant (up to 1.98 pounds is fine), then we should not suspect an 'overcharge'.

Unfortunately....replacing the TXV requires evacuation of the system and removal of the Evaporator. It isn't as difficult job on an 80 series as it is with a 100 series and provides an opportunity to inspect and clean the Evaporator. It will be pretty dirty in most cases.

If you live in 'Bama' then you have high levels of humidity. On a typical Summer Day you should be seeing a good amount of condensation run off when your A/C system is working correctly. Since you are not....we know right there something is amiss.

I replaced the expansion valve today and recharged it. It held 250 to 275 psi on the high side at idle with a shop fan in front. It was 95F in the shop. Misting the condenser with water would drop it down to 200 psi. After cleaning the absolutely nasty and caked up evaporator I'm getting a lot of condensate dripping.

Does that high side psi sound normal for idle at 95F ambient?

Thanks to everyone who replied and helped out with this. I learned a lot and I'm pretty sure it's fixed.

 

[RiverCityDave]

Right On!!!

 

[jbc28]

We all roll the dice sometimes and it could have worked out well for you. Removing/cleaning the evap is worth doing, esp. if you don't know the rigs history. I'll bet you find a decent layer of cruft on the evap.

You were correct. It was nasty

 

[flintknapper]

I replaced the expansion valve today and recharged it. It held 250 to 275 psi on the high side at idle with a shop fan in front. It was 95F in the shop. Misting the condenser with water would drop it down to 200 psi. After cleaning the absolutely nasty and caked up evaporator I'm getting a lot of condensate dripping.

Does that high side psi sound normal for idle at 95F ambient?

Thanks to everyone who replied and helped out with this. I learned a lot and I'm pretty sure it's fixed.

Your high side pressure does sound normal. But to expand on High and Low side pressures:

1. The main purpose for using a manifold gauge set is as a diagnostic tool to determine the relative health/function of the system.

2. High and low side pressures give us an 'idea' of where we should be within (windows) with respect to the refrigerant charge since we know the temperature/pressure relationship of a given refrigerant.

3. High and low side pressure readings are most beneficial when you are charging a partially filled system since we do not know the exact amount of refrigerant (by weight) the system contains.

4. Ideally....we would want to start with a completely evacuated system and then WEIGH in the refrigerant amount.
This will always be the most accurate method to fill the system.

5. The FSM will suggest certain pressures but can't account for every local condition the vehicle is under. Further....it asks you to look for the presence (or lack of) bubbles in the sight glass. I would completely dispense with the latter method unless you are way out in BFE and have no tools of any type.

6. My goal when doing my own A/C work is to achieve the best 'Vent Temps' the system is capable of under given ambient temps. To that end....I will take the time to add or subtract the refrigerant charge by small amounts while monitoring the vent temps. As long as the high and low side pressures remain within safe limits....I give them no further thought. There simply isn't an 'ideal' number you should be at. Only 'windows' that are considered normal and safe.

In summary...I am not saying ignore manifold pressures. I am just saying they are not the final word with respect to best system performance. Too many variables to be considered. If you have the luxury of starting a with an empty system, then 'weigh' in the initial charge. IF this gives you satisfactory vent temps, you're done. IF you want to fine tune the system, add or subtract small amounts and you'll find the spot of diminishing returns.

 

[jbc28]

Your high side pressure does sound normal. But to expand on High and Low side pressures:

1. The main purpose for using a manifold gauge set is as a diagnostic tool to determine the relative health/function of the system.

2. High and low side pressures give us an 'idea' of where we should be within (windows) with respect to the refrigerant charge since we know the temperature/pressure relationship of a given refrigerant.

3. High and low side pressure readings are most beneficial when you are charging a partially filled system since we do not know the exact amount of refrigerant (by weight) the system contains.

4. Ideally....we would want to start with a completely evacuated system and then WEIGH in the refrigerant amount.
This will always be the most accurate method to fill the system.

5. The FSM will suggest certain pressures but can't account for every local condition the vehicle is under. Further....it asks you to look for the presence (or lack of) bubbles in the sight glass. I would completely dispense with the latter method unless you are way out in BFE and have no tools of any type.

6. My goal when doing my own A/C work is to achieve the best 'Vent Temps' the system is capable of under given ambient temps. To that end....I will take the time to add or subtract the refrigerant charge by small amounts while monitoring the vent temps. As long as the high and low side pressures remain within safe limits....I give them no further thought. There simply isn't an 'ideal' number you should be at. Only 'windows' that are considered normal and safe.

In summary...I am not saying ignore manifold pressures. I am just saying they are not the final word with respect to best system performance. Too many variables to be considered. If you have the luxury of starting a with an empty system, then 'weigh' in the initial charge. IF this gives you satisfactory vent temps, you're done. IF you want to fine tune the system, add or subtract small amounts and you'll find the spot of diminishing returns.

Good info. Thanks. I added 860g yesterday. It seems to be cooling fine. I will get some vent temps soon. Hopefully, this new expansion valve won't stick like the old one. I do think the old one was the original. It was a denso part, and I didn't see any evidence of someone being in there. I also replaced all of the foam gaskets on the evap box. They were falling apart. I could not feel any leaks around it once reinstalled.