evaluating an AC compressor when system is currently discharged - Page 11 - PeachParts Mercedes-Benz Forum

ROLLGUY · #**151** 07-10-2018, 07:57 PM

Quote:

Originally Posted by kuene

I hear ya.

If i'm going to go through all the trouble to take the compressor off, then I'll probably want to spend a couple hundred to put an actual correct one back on - with the right clocking and the right pulley size.

Unless there is a way to change thee clocking while leaving it on, I'm probably going to consider getting a new one. I don't see any reason to reseal this one, I just bought it.

Also, just to note, I think its clocked at 90 degree difference than the proper one - not 180 (9 versus 12). But doubt that matters.

I just have to consider if I want to go through all the work again right away - it was difficult for me. at this point money is less my worry.

Welcome to the R4 nightmare, I had the same nightmare many years ago. That was the last time I installed an R4 in one of my cars. I installed a "rebuilt" unit. After charging the system, it was found to be defective, and the second one was bad straight out of the box. I didn't even bother installing it. I sought out a better compressor, and found a Sanden. I made a bracket to adapt it to my OM617 (1984 300SD). The rest is history.....Rich

funola · #**152** 07-10-2018, 08:20 PM

Quote:

Originally Posted by ROLLGUY

Welcome to the R4 nightmare, I had the same nightmare many years ago. That was the last time I installed an R4 in one of my cars. I installed a "rebuilt" unit. After charging the system, it was found to be defective, and the second one was bad straight out of the box. I didn't even bother installing it. I sought out a better compressor, and found a Sanden. I made a bracket to adapt it to my OM617 (1984 300SD). The rest is history.....Rich

Probably operator error or bad luck or both. 94 F here today, 40 F vent temp with a (2 year old now) 4 Seasons remanufactured R4 with R12 refrig, all original hoses, condenser, evaporator.

ROLLGUY · #**153** 07-10-2018, 08:33 PM

Quote:

Originally Posted by funola

Probably operator error or bad luck or both. 94 F here today, 40 F vent temp with a (2 year old now) 4 Seasons remanufactured R4 with R12 refrig, all original hoses, condenser, evaporator.

Not everyone has the nightmare, but sadly many do. Consider yourself blessed to not have experienced the R4 nightmare.

kuene · #**154** 07-10-2018, 09:26 PM

My R4 situation is presently entirely due to the fact that I bought the wrong part and cannot be (at this time) blames on the R4 design itself.

97 SL320 · #**155** 07-10-2018, 09:52 PM

As I asked in post 150 WHAT SITUATION?

funola · #**156** 07-10-2018, 10:10 PM

Even if the lube hole clocking is incorrect, it would take much longer IMO (years) before the main shaft seal starts to leak due to insufficient lubrication. Clocking for the clutch connector don't matter as long as your harness is long enough to reach it. If you are not leaking refrigerant, clocking is not your problem.

Here's some Photobucket pics in posts #42 - 44 dissembling R4 compressor of the lube hole and how it's marked by an X. This was from many years ago when I took apart an R4. If your's has the x at 12 o'clock on the aluminum seal carrier/ cover, it is clocked correctly.

funola · #**157** 07-10-2018, 10:19 PM

Quote:

Originally Posted by ROLLGUY

Not everyone has the nightmare, but sadly many do. Consider yourself blessed to not have experienced the R4 nightmare.

My success in getting my AC to work is not because I was blessed. It is from willing to learn, being persistent, not give up easily, being able to differentiate good advice from BS. Automotive AC is not easy. I had my share of failures before finally getting it to work well.

vwnate1 · #**158** 07-10-2018, 11:17 PM

...With envy ! .

I'm lucky to get 60* F at the dash outlets .

I went through living hell to make the Klima I on my 1980 300CD working, the R4 compressor never gave me a lick of trouble, I ran R12 in it and nearly froze in Death Valley .

Agreed, AC can be a PIA if you don't do it regularly .

Diseasel300 · #**159** 07-10-2018, 11:31 PM

Quote:

Originally Posted by funola

My success in getting my AC to work is not because I was blessed. It is from willing to learn, being persistent, not give up easily, being able to differentiate good advice from BS. Automotive AC is not easy. I had my share of failures before finally getting it to work well.

^^^ This.

Separating the BS (and BOY is there a lot of it) from reality is the biggest key. If you pay attention to all the "experts" on the Internet, you'll quickly come to the conclusion that the A/C will never work, the design is flawed, it'll never cool off in the summer, all the hoses will leak, and the compressor will blow up.

Push all that crap aside, R&R the system with common sense and follow basic guidelines of servicing HVAC equipment and it'll blow cold. Like Funola, I'm running a stock system with reman compressor, R134a expansion valve, and new filter/dryer. Running on 134a, I'm blowing 40-44˚ at the center vent with it 95+ outside and no window tint. This is season 2 and still no leaks on the original 1986 hoses. I'm impressed for a 32 year old car, but it works better than my 2011 Honda (which has DARK tint) in exactly the same conditions.

R&R work on automotive A/C systems is not rocket science, nor is it voodoo. It just takes patience and a methodical approach. Do it right, take your time, and be thorough in your practices and you'll be rewarded with a comfortable car and a reliable A/C. Take shortcuts, skip steps, or overthink it and you'll complain about how poorly your A/C works and how it's always breaking down.

kuene · #**160** 07-12-2018, 09:59 AM

sorry 97 SL - I was referring to the situation that a few commenters pointed out: That because I have an incorrectly clocked r4 installed, the oil port that would be part of the compressor lubrication system is not in the right orientation for gravity to do its work - thus apparently dooming the compressor to a shorter lifespan.

I also have a new separate situation (mentioned in another thread started after I posted the update here) where my cool air started blowing warm on a highway driver this weekend. After turning off and parking for a while, it was back to cool, but I'm trying to diagnose that - to be clear, I don't belive that is at all connected to the clocking issue though. Thinking it could be restriction, or ETS malfunction, or maybe under/overcharge, or perhaps incorrect oil amount? hard to say at this point.

Quote:

Originally Posted by 97 SL320

As I asked in post 150 WHAT SITUATION?

97 SL320 · #**161** 07-12-2018, 07:31 PM

Quote:

Originally Posted by kuene

That because I have an incorrectly clocked r4 installed, the oil port that would be part of the compressor lubrication system is not in the right orientation for gravity to do its work - thus apparently dooming the compressor to a shorter lifespan.

I'm not convinced that orientation of the oil hole matters. With all the pulsation going on inside the compressor crank case it likely does not matter. Even if it did, any sort of front needle bearing / front seal failure would be pretty far down the road.

One way to find out for sure if the hole matters is look at a GM factory manual for a car that uses this compressor ( lots of mid 70's / mid 80's stuff )

Quote:

Originally Posted by kuene

I also have a new separate situation (mentioned in another thread started after I posted the update here) where my cool air started blowing warm on a highway driver this weekend. After turning off and parking for a while, it was back to cool, but I'm trying to diagnose that - to be clear, I don't belive that is at all connected to the clocking issue though.

Apparently this is the thread

Bad new ac low pressure cuttoff switch?

Correct, oil clocking has nothing to do with a iced evaporator.

Quote:

Originally Posted by kuene

Thinking it could be restriction,

This won't cause evap icing.

Quote:

Originally Posted by kuene

or ETS malfunction,

What is an ETS?

Quote:

Originally Posted by kuene

or maybe under/overcharge,

Under charge can lead to icing of the evap because low side pressure is too low causing the evaporating liquid to absorb too much heat.

Over charge will result in high side pressures being too high.

I haven't done a R12 to R132 conversion, but some searching shows 85 - 90 -95 % of R12 capacity.

Try to get some accurate pressures, wait for the low side to get to it's minimum and take the high side at that moment. To calculate pressure ratio, add 15 to each pressure then divide low into high.

From your prior post (low side was like 25 high side around 230-250 maybe)

25+15 = 40 ______ 230 + 15 = 245 _______ 250 + 15 = 265

1 to _______________6.12 _________________ 6.62

According to https://www.cpsproducts.com/wp-content/uploads/CTK1300A_manual.pdf

R12 needs 5 - 6 to 1

R132 needs 6 - 7 to 1

When you operate the AC, does the discharge line from the evaporator get cold? ( This is the one between the evaporator and compressor ) If the line isn't cold, the system is undercharged.

Quote:

Originally Posted by kuene

or perhaps incorrect oil amount?

Too much oil reduces efficiency because oil starts to coat the condenser / evaporator piping. Too little oil won't cause the evap to ice up.

Quote:

Originally Posted by kuene

hard to say at this point.

Is your condensation drain clogged?

Do you have a wiring diagram for the clutch control / pressure / temp switches? Something needs to shut the compressor off when evap temp is low or suction pressures is too low.

A factory manual describing how this particular system operates would be valuable.

kuene · #**162** 07-13-2018, 11:05 AM

ETS is what I've seen some people/docs refer to the "evaporator temp sensor" as.

I'll get accurate pressures using the method you and others described. I don't have the mercedes CC manual, but in the Haynes AC book, there is a table of pressures and for 82 mercedes diesel I think the high pressure was supposed to be around 230-250 or so. No idea if those tables in that book are to be trusted.

for the r134 charge I put in exactly 80% of the r12 weight specified on my radiator support tag - I read up on the ranges from 75-90% and did not want to over charge initially.

If the condenser drain is that foam tube that goes down into the transmission tunnel - I replace that disintegrated engineering marvel (foam???) a while ago with a piece of rubber from a garbage disposal drain kit. I have what looks like normal condensation draining out from under the car when the AC is in use.

the electrical wiring/relays and such related to the fan and compressor appear to be functioning correctly. temp and pressure switches on receiver are new (as is receiver). If one of those switches were faulty, would they default to OFF or on? Compressor is working so should I assume that switch is getting enough pressure to complete the circuit?
`

Quote:

Originally Posted by 97 SL320

I'm not convinced that orientation of the oil hole matters. With all the pulsation going on inside the compressor crank case it likely does not matter. Even if it did, any sort of front needle bearing / front seal failure would be pretty far down the road.

One way to find out for sure if the hole matters is look at a GM factory manual for a car that uses this compressor ( lots of mid 70's / mid 80's stuff )

Apparently this is the thread

Bad new ac low pressure cuttoff switch?

Correct, oil clocking has nothing to do with a iced evaporator.

This won't cause evap icing.

What is an ETS?

Under charge can lead to icing of the evap because low side pressure is too low causing the evaporating liquid to absorb too much heat.

Over charge will result in high side pressures being too high.

I haven't done a R12 to R132 conversion, but some searching shows 85 - 90 -95 % of R12 capacity.

Try to get some accurate pressures, wait for the low side to get to it's minimum and take the high side at that moment. To calculate pressure ratio, add 15 to each pressure then divide low into high.

From your prior post (low side was like 25 high side around 230-250 maybe)

25+15 = 40 ______ 230 + 15 = 245 _______ 250 + 15 = 265

1 to _______________6.12 _________________ 6.62

According to https://www.cpsproducts.com/wp-content/uploads/CTK1300A_manual.pdf

R12 needs 5 - 6 to 1

R132 needs 6 - 7 to 1

When you operate the AC, does the discharge line from the evaporator get cold? ( This is the one between the evaporator and compressor ) If the line isn't cold, the system is undercharged.

Too much oil reduces efficiency because oil starts to coat the condenser / evaporator piping. Too little oil won't cause the evap to ice up.

Is your condensation drain clogged?

Do you have a wiring diagram for the clutch control / pressure / temp switches? Something needs to shut the compressor off when evap temp is low or suction pressures is too low.

A factory manual describing how this particular system operates would be valuable.

97 SL320 · #**163** 07-13-2018, 02:27 PM

Quote:

Originally Posted by kuene

ETS is what I've seen some people/docs refer to the "evaporator temp sensor" as.

Do we know if this is electronic or mechanical?

Other older brands are mechanical using a sealed system consisting of a sensing bulb / capillary tube / thermostat to sense evap temp. Basically, this is a remote sensing device where the sensing bulb and tube are filled with gas that expands when hot and contracts when cold. This gas presses on a diaphragm that then actuates a switch. If this gas escapes, the switch will think things are hot and let the compressor run.

There are also situations where worn contacts will weld themselves together causing the switch to stick on.

If you have such a system, is it possible to bring the sensing bulb out and stick it in an ice bath for testing?

Quote:

Originally Posted by kuene

I'll get accurate pressures using the method you and others described. I don't have the mercedes CC manual, but in the Haynes AC book, there is a table of pressures and for 82 mercedes diesel I think the high pressure was supposed to be around 230-250 or so. No idea if those tables in that book are to be trusted.

A pressure chart for R12 won't work with a R132 system so using pressure ratios will be needed.

Quote:

Originally Posted by kuene

for the r134 charge I put in exactly 80% of the r12 weight specified on my radiator support tag - I read up on the ranges from 75-90% and did not want to over charge initially.

Lets see what the actual pressures show.

Quote:

Originally Posted by kuene

If the condenser drain is that foam tube that goes down into the transmission tunnel - I replace that disintegrated engineering marvel (foam???) a while ago with a piece of rubber from a garbage disposal drain kit. I have what looks like normal condensation draining out from under the car when the AC is in use.

Yep some sort of drain tube. Given you have water coming out, it should be OK.

Another thought, I've pulled a few evaporators on various cars that had leaves and other debris clogging the fins, this would lead to reduced air flow and icing.

Is there any way to look inside the AC box?

Quote:

Originally Posted by kuene

the electrical wiring/relays and such related to the fan and compressor appear to be functioning correctly. temp and pressure switches on receiver are new (as is receiver). If one of those switches were faulty, would they default to OFF or on? Compressor is working so should I assume that switch is getting enough pressure to complete the circuit?
`

My concern is that something was jumpered in the the past allowing the compressor not to cycle when low side pressure drops too low / evap temp is too low. A factory manual would offer principles of operation, from there we can figure out what it going on.

Diseasel300 · #**164** 07-13-2018, 02:37 PM

Just so we're clear, it's R134a, not R132.

In the other thread, it's already been suggested to check the ETS (evaporator temperature switch). On the earlier W123's it was a mechanical switch with a sensing bulb. Later SD's and 1986+ vehicles used a thermistor and an electronic sensing system. Not sure if the W123 ever switched over to the electronic variety, I'd suspect not.

The ETS and the CCU are the only things that will cycle the compressor on and off. If a later dual-pressure switch was installed on the receiver/dryer, then high head can trip the compressor off. There is no low pressure switch to cycle the compressor, that function is performed by the ETS and the CCU when the thermostat is satisfied.

It's already been suggested that Kuene check and clean the evaporator coil. They get absolutely filthy after decades of use and a dirty evaporator WILL cause icing of the coil. Frozen coil will also cause low suction pressures and can cause liquid refrigerant to make it back to the compressor (not good).

If the coil is freezing up, about the only thing in the circuit that will cause it is the ETS or a stuck clutch relay (there is no Klima relay on this car). Since the compressor kicks on and off with the CCU, that pretty well rules out the clutch relay.

BillGrissom · #**165** 07-14-2018, 12:46 AM

Re the evaporator temperature switch (anti-icing switch, ETR to M-B), see my recent post (AC Fix 1983 300D). Yes, you can remove and test (mine was bad). I replaced w/ a $10 one for a Pontiac, but P-P sells them. If it sticks closed, I think nothing will limit the compressor running, until pressure builds to where a hose blows or the clutch slips and melts. Changing to a binary pressure switch seems smart.

Re R4 vs Sanden. I had both on my 1985 (Sanden w/ Rollguy's brackets). Both worked and I can't say the Sanden was colder from the vents. But, I kept the OE condenser and the heater servo-valve can leak so you get heat which can overwhelm the AC. The later is often problematic so adds another variable to any comparisons.