Air Conditioner Mystery

[steveawitt]

1992 525i 120,000 miles

My Ac will not work and it really has me stumped.
I would appreciate any help.

Everything works, but it will not get cold.
New compressor
new expansion valve
new dryer.

………………………………………….. ……………………
I blew out all the tubes with air compressor when I had it apart.
put it back together pulled a vacume (no leaks)
added half a can of r134 , compressor kicks on, and low side shot up to 90 psi,…

Topic

[John B Kobberstad]

Quoted From steveawitt:

1992 525i 120,000 miles

My Ac will not work and it really has me stumped.
I would appreciate any help.

Everything works, but it will not get cold.
New compressor
new expansion valve
new dryer.

………………………………………….. ……………………
I blew out all the tubes with air compressor when I had it apart.
put it back together pulled a vacume (no leaks)
added half a can of r134 , compressor kicks on, and low side shot up to 90 psi,…
high side 0.
shut compressor off and they equlize. this is odd?????
I don’t understand why it only takes a half a can or 134 and the pressure shoots up so high??

If I run the compressor for a while at 40 psi on the low side, nothing gets cold.
I checked all the tubes nothing cold.
………………………………………….. ………………………
The ac button engages, ( blue dot on dial turned down) ,the condenser fan comes on, inside temp gage works, compressor kicks on, blower fan on.

If anybody has any ideas I could really use some help. thanks

1- You need to do a proper system flush rather than blow out with air compressor. If the compressor you replaced had a catastrophic failure you’ve got some bad stuff in the system and flushing is required or the new compressor will meet the same fate as the one that was replaced. Before you put that new compressor into service you should have rotated the clutch plate a couple times to circulate the oil in the compressor so everything inside it is lubed and ready to go.
2- Should have replaced all the O rings when you had the system apart.
3- I don’t see anything about adding the proper viscosity oil and the proper amount of it to the system. You need to reduce the amount the system requires by the amount that comes in the new compressor and use the same viscosity and maybe add some dye in with it.
4- Don’t know how you pulled a vacuum, or how you checked for leaks.
5- If everything is working correctly it should work. Something(s) is(are) NOT working this is obvious.
6- Did you check to see what the proper amount of R 134a is supposed to be in the system?

You may have debris in the system causing a blockage and your new compressor may have been destroyed by the debris that was not cleaned out of the system. I hope this is not the case though.

[spelunkerd]

So, if I am reading you correctly, low side pressure rises when compressor starts, high side doesn’t change. Would it be possible to have accidentally hooked the new compressor up backwards?

[college man]

all great posts above. how much charge does the system take total?
how much is a 1/2 can of r134a? when the compressor was replaced
did you remove the caps that cover the ports of the new compressor.
make sure you can account for them.

[John B Kobberstad]

Sorry I missed that it is a 1992, so –

Are you running original system (R 12) or has this already been converted over? Is new pump replacement for original (R 12) or is it an equivalent to be able to run R 134a? Using R12 gages or R 134a gages?

[Matt]

Quoted From spelunkerd:

So, if I am reading you correctly, low side pressure rises when compressor starts, high side doesn’t change. Would it be possible to have accidentally hooked the new compressor up backwards?

I’m on this same train of thought. I’m not sure if it’s possible to hook the compressor up backwards, but if so, then that makes perfect sense. Otherwise, make sure you have your gages on the right ports. If it’s an R-12 system, then the connectors are identical. It’s more likely that the high side is getting high fast, and the low side is getting nothing. This could be due to a clogged metering device (orifice tube, thermal expansion valve) and the high and/or low side pressure sensors aren’t seeing what they want to see, and that’s shutting off the compressor.

[steveawitt]

Thanks again

under the hood it says 3 + lbs that is around 55 oz. no where near 8 oz that it takes now.
I add my charge thru the small tube I assumed that was the low side. that is how my gages are set up.
I did not check how much oil was in the comp. when I got it , I took the caps off and turned it by hand and oil emediatly started coming out so i assumed that it had the right amount of oil in it. What would happen if it had way to much oil in the comp.?

steve

[EricTheCarGuy]

It could be that you have a restriction somewhere in the low psi side, it’s not uncommon to have an issue like this after a conversion. This one is tough because I believe you’re probably hooked up correctly. You may be able to use an inferred thermometer to find the restriction if you follow the hoses along their path looking for a sudden change in temp.

[steveawitt]

Wow!
Thanks for all the input.
When I blew the tubes out; the comp. , the exp. valve , the dryer were all off.
I watched the other end as the old refridgerent came out., I saw no contamints or noticed any blockage. ( I was looking for it).
installed new exp. valve , comp., and dryer. Turned comp. by hand 7 times.
Comp. came with oil in it (mistake ? )

?I pulled a vacum with a vacum pump, and let it run for about an hour.
I used a cheap vacum pump that you hook up to your air comp. from Harbor Frieght.,
So I don’t really know how much vacume I pulled (Mistake? )

?Converted to r134 used R134 gauges.
You cannot hook the comp. up backwords. Low side ,small tube? High side, large tube.? charged low side small tube.
It took about 3/4 of a 12 oz. can of R134.
low side shoots up to 90 psi, comp. starts and it drops to about 70 psi. High side, (large tube) drops to 0 shut comp. off and they equilize .
I reduced the pressure to about 35 psi on the low side and let the comp. run for 10 min. then checked the tubes coming off the comp. to see if they were cool ,they were not.

I am not sure of the total wieght of coolant my system takes, I was going by pressure. I will find out.
Thanks for your help.

[John B Kobberstad]

Quoted From steveawitt:

“Wow!
Thanks for all the input.
When I blew the tubes out; the comp. , the exp. valve , the dryer were all off.” Off the vehicle?? A/C cleaning solvent must be used to clean the system.

“I watched the other end as the old refridgerent came out.” Refrigerant MUST BE RECAPTURED by law!!! Unless you have the proper equipment to do it, take it in to a licensed refrigerant removal site. What about the oil? It should have come out also and needs to be replaced. “, I saw no contamints or noticed any blockage.” Contaminents are very small and not easily seen. “( I was looking for it).
installed new exp. valve , comp., and dryer. Turned comp. by hand 7 times.” This is good to have been done.
“Comp. came with oil in it (mistake ? )” No mistake, they usually do. but more must be added. Subtract what is required for the compressor from the total amount needed for the system and add oil accordingly.

“?I pulled a vacuum with a vacuum pump, and let it run for about an hour.
I used a cheap vacuum pump that you hook up to your air comp. from Harbor Freight.,” Not the right kind of pump for A/C work. You probably still have moisture in the system and this will cause acid to form in the system and a pressure increase.
“So I don’t really know how much vacuum I pulled (Mistake? )” What did your gages tell you? Should go negative pressure to -30 (Atmosphere)

“?Converted to r134 used R134 gauges.” Quick connects with different size for Hi and Low? If yes then it was probably converted. Correctly???

“You cannot hook the comp. up backwords. Low side ,small tube? High side, large tube.? charged low side small tube.
It took about 3/4 of a 12 oz. can of R134.” If you still have moisture in the system it might be hard to get more refrigerant in and since you have refrigerant in, you need to take the vehicle in to a licensed removal site and have the system evacuated of the refrigerant before trying to remove the moisture again yourself.

“low side shoots up to 90 psi, comp. starts and it drops to about 70 psi. High side, (large tube) drops to 0 shut comp. off and they equilize .
“I reduced the pressure to about 35 psi on the low side and let the comp. run for 10 min. then checked the tubes coming off the comp. to see if they were cool ,they were not.” How are YOU reducing the low side pressure to 35 psi?

I am not sure of the total wieght of coolant my system takes, I was going by pressure. You need to have the correct amount of oil in the system and must be the same viscosity as the oil in the pump. Call the manufacturer of the pump to find out what oil they use for your pump. I will find out.

Thanks for your help.

Bottom line — If you want the A/C to work take it in to a professional.

[college man]

something backwards. The high side is the small line and the bigger
line is the low side. find the tag under the hood for the original R-12
I will help you calculate the R134A system charge.

[college man]

your system charge should be 47-48 oz or 3lbs of r134a
your greatly under at 8oz

[steveawitt]

Mystery Solved!!!

Yea…… College Man was right. When I conveted to r134 I put the large nipple on the large line. The large nipple is for the high side the large tube is the low side.
I have been trying to charge the high side. swaped them out and it took a charge right away.
Thanks for all the help.
Steve

[Mike]

Change the traffic light to green.

[dreamer2355]

Thanks for posting the fix and using the ETCG forums!

[EricTheCarGuy]

Glad you got it sorted out thanks for keeping us up to date and for using the ETCG forum.

[Author]

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