A/C Help

[mLuMaN83]

So heres the deal. When I get in the car, the AC blows great. Ice cold. But then after say 20 min or so, it decides to go luke warm. Also if I change to face and defroster, I feel cold air through the face vents for a second then goes luke warm again and blows hot air out the defroster. If I turn the car off for awhile and get back in, the AC works fine again and then after a bit, goes luke warm. I brought the car in last year for an evac and recharge and they said it was full and pressure was good and that they think the issue may be in the AC control unit itself.

Do I actually need an evac and recharge? Or could it be the control unit?

[kayger12]

See if the air on the drivers side is colder than the air on the passenger side when you're putting it through the dash vents.

[mLuMaN83]

It is slightly cooler on the drivers side then the passenger side. The odd thing here is that if the car sits awhile or overnight, and I jump in and go, the air is ice cold for about 20 min then all the sudden, it goes warm.

[kayger12]

I've read before that temperature differential between the two sides is a sign of low refrigerant.

I'd start there and then move on to trouble shooting the compressor.

Can the FSR affect that or is it only the blower speed?

[mLuMaN83]

Blower is fine. It's almost like the control unit is telling the flaps to do the wrong thing because if I change the vent, i feel ice cold for a second come out the face vents. I and thinking of buying a cheap used control unit off ebay and see what happens. If that doesnt work, then maybe go for an evac and recharge.

Weird weird. Either way, it's gotta get fixed. I live in Florida.

[LivesNearCostco]

Set your OBC to display exterior temp, see if it's roughly accurate. If it displays a much lower exterior temp than outside, it could shut off the A/C because it thinks it's cold outside. Or maybe your heater valve is broken?

[echo46]

I agree with KG, sounds like low refrigerant. You can hook up an AC guage and check the pressure to see if it needs a boost. You aRe checking the vacuum and pressure psi of the system. The high and low pressure can diagnose a lot of problems. Fairly easy. If you are doing it yourself, don't allow any to escape as it is fairly toxic and there are strict environmental laws concerning its capture. If you suspect a leak, which I don't here, you can put a tracer dye in the system serif it appears at any of the connections or the compressor. I replaced most of the AC system on my E36. Not that difficult.

[telijah]

It is not indicative of low refrigerant. Low refrigerant would not have cool air one moment then warm the next over and over. It is likely what LiveNearCosco said. There is also a water valve under the hood that I believe I've heard cause similar symptoms, #2 here (http://www.realoem.com/bmw/showparts.do?model=AV53&mospid=47725&btnr=64_0890&hg=64&fg=18).

To answer Kayger's question about the FSR, the FSR only shows symptoms of erratic or no blower control.

[echo46]

Couldn't the compressor be going bad also?

[WOLFN8TR]

You also need to get a pocket thermometer to check the temp coming out of the vents. A Low charge will make the compressor cycle on/off. My AC blows approx 35-38 degrees on Max. Good luck!

[kayger12]

Was looking at the Bentley. There's an evaporator temp sensor that needs to be above a certain temp for the compressor to operate. If that sensor is wonky it can kick the compressor offline.

Just another idea to add to the troubleshooting list.

[danewilson77]

Was looking at the Bentley. There's an evaporator temp sensor that needs to be above a certain temp for the compressor to operate. If that sensor is wonky it can kick the compressor offline.

Just another idea to add to the troubleshooting list.

HTC DNA, Williamsburg, VA

[mLuMaN83]

Oh boy, I've got a lot to look at. Cofused. On a good note, AC worked for my entire drive this evening. Woot. I think it is some sort of sensor or the control unit. It does not seem "mechanical". Seems like an "intellegent" problem.

[mLuMaN83]

AC worked all day today without going warm.

[kayger12]

Weird. Let me know of you want to look into that sensor and I'll dig the info out of the Bentley.

Sent from the Last Next Best Thing.

[KevinC]

I'm in a similar pickle, I've got ice cold air out of the left side vents (driver door and left half of center vent), and warmer air out of the right side, with the far right being slightly warmer than the center right. WTF? It's already triple-digits here in the Sonoran desert, and we still have a month of spring left before it REALLY heats up - so this is not a good situation. So does that sound like low refrigerant? I sure hope that's what it is, I dread it being anything like any of the flaps, motors or ducts in the dash, because tearing all that apart sounds ugly expensive, before the ugly expensive parts cost even kicks in. I'm a little skeptical that it's that simple, I wouldn't expect arctic air blowing out of one side with the refrigerant going low, but maybe? Any wisdom appreciated before I haul it into my local indy.

[kayger12]

^ From everything I've read over the years, cold on the drivers side and warmer on the passenger side indicates low refrigerant.

Hopefully it's that simple in your case.

Sent from the Last Next Best Thing.

[mLuMaN83]

Yeah I will do Kayger. I've got to get a moment to dedicate to doing some diagnosing. I would love to just bring it in to BMW and get a diag done but the money is outrageous.

[kayger12]

Agreed. That's a good last resort option of you can't get it figured out.

Sent from the Last Next Best Thing.

[LivesNearCostco]

Kayger, my car is obviously in sympathy with yours, because yesterday my final stage resistor gave out. At least that's what it seems like. First the heat became sporadic (A/C was still working). Then with car stopped and key out, blower fan kept going but no other HVAC controls worked. Pulling blower fan fuse stopped the fan, and replacing another 5A fuse gave me control back of the HVAC settings (but still no fan).

[kayger12]

Kayger, my car is obviously in sympathy with yours, because yesterday my final stage resistor gave out. At least that's what it seems like. First the heat became sporadic (A/C was still working). Then with car stopped and key out, blower fan kept going but no other HVAC controls worked. Pulling blower fan fuse stopped the fan, and replacing another 5A fuse gave me control back of the HVAC settings (but still no fan).

Mine is actually fine. OP is chasing the gremlin.

Yours definitely sounds like the FSR.

Been there on the 325. Easy fix (unless you have big hands).


Sent from the Last Next Best Thing.

[3ZHP]

So heres the deal. When I get in the car, the AC blows great. Ice cold. But then after say 20 min or so, it decides to go luke warm. Also if I change to face and defroster, I feel cold air through the face vents for a second then goes luke warm again and blows hot air out the defroster. If I turn the car off for awhile and get back in, the AC works fine again and then after a bit, goes luke warm. I brought the car in last year for an evac and recharge and they said it was full and pressure was good and that they think the issue may be in the AC control unit itself.

Do I actually need an evac and recharge? Or could it be the control unit?

I started having the exact problems last weekend, still looking for a quick solution before a long road trip this weekend. Please keep me posted if you find something and I will do the same. FYI; mine's an 03 with 130k

[Dave_B]

If any of your suspect a low freon issue, make sure you have the place that refills it put dye in the system.

Cooling systems are closed loop systems so it shouldn't be losing freon. If it is, there is a leak. The blacklight reactive dye will show up with certain glasses and a black light.

[LivesNearCostco]

got home, new FSR arrived. Going in now to try to replace.

Mine is actually fine. OP is chasing the gremlin.
Yours definitely sounds like the FSR.
Been there on the 325. Easy fix (unless you have big hands).
Sent from the Last Next Best Thing.

[danewilson77]

got home, new FSR arrived. Going in now to try to replace.

Gawd I hated replacing that.

HTC DNA ON TT4 BETA, WILLIAMSBURG, VA

[ryankokesh]

I'm dreading doing my blower.

[3ZHP]

Found this on E46Fanatics on a similar thread, and will probably try it first.

"This was also my experience. I described the symptoms to my (very honest, very knowledgeable) independent BMW mechanic, and he had never heard of the heater control valve going bad. His contacts in the BMW parts supply business also denied knowledge of any HCV's requiring replacement. He was, therefore, reluctant to replace a part that he didn't believe was the culprit.

So, I replaced it myself, which took less than 30 minutes (with a helper). Nearly 3 years later, I consider the problem fixed. My advice: get the part (64118369805) online (less than $100; $68.62 currently at http://getbmwparts.com/) and replace it yourself. There's a reasonable chance that that will correct the problem. If not, you'll at least know to look elsewhere."

http://forum.e46fanatics.com/showthread.php?t=594925&page=2

[KevinC]

Had mine fixed last week.. as suspected, the cool on the left/warmer on the right was being caused by a lack of refrigerant. My indy added a pound, leak and overall tested the system (good), and now I'm chillin' like an eskimo. Except on days like today, where my car is out in an uncovered parking lot all day, and it's 110 when I get in at 5pm, with only a 20-minute ride home. Gee, and it's still more than 2 weeks before summer even starts. O joy!

[wertyu78]

Expansion valve

[LivesNearCostco]

Ryan, I replaced my blower 2 years ago. It was 3x the work of the FSR, though the FSR requires more contortionist skills. FSR requires removing about 3 parts (not including FSR). Blower fan requires removing at least 7 parts (not including blower itself) and clipping the new blower in is a hassle.

I'm dreading doing my blower.

My FSR was held in only by a retention clip, no screws. The module in front of it did have 2 torx screws. My replacement Uro FSR looked exactly like the old BMW/Behr FSR. Not sure if that means both are the old, bad design, or my car was born late enough to get the revised FSR. After all my original one did last 10 years!
With new FSR, fan blows stronger at lowest setting than it did before.

Shortly before FSR failed completely the heater function became unreliable. I could control fan speed but heat would sometimes come on, sometimes not. When FSR failed the fan ran at medium-high all the time even with key out of ignition. When pulling the 40A fuse to stop fan, I found one of the 5A fuses for the A/C was blown. My theory is that blown fuse controlled one of the servos that moves the flaps. Other possibility is failing heater control valve or air trapped in the system.

On A/C recharge... I recently recharged the minivan. First I bought R134a with leak stop and oil but no dye. Then a few weeks later I added more 134a which had dye but no oil or leak stop. Doesn't someone make R134a that has oil, dye, and leak sealer?

[mLuMaN83]

Any update 3ZHP? I have not had the time or funds to get into this yet. Getting ready for fall classes and becoming a Florida resident again...

Although I made a 2 hour trip into St Augustine to get some waves and AC stopped 30 min into the trip. Had to roll down the windows at 92 degrees. Thankfully it worked for most of the trip back. Freekin weird. I'm usually pretty good at diagnosing but this one has me stumped.

[3ZHP]

I started having the exact problems last weekend, still looking for a quick solution before a long road trip this weekend. Please keep me posted if you find something and I will do the same. FYI; mine's an 03 with 130k

The 1200 mile road trip seamed to have fixed the problem for now.:dunno

[mLuMaN83]

It will be back. I have had months go by with no issues in the past but it has returned with vengeance now that I am here in Florida. If it is in fact the same thing. I still have a hunch it is the control unit itself. Something is making the flaps go wacky from time to time. I hope I can get this solved and help people with the same problem in the future. This is a weird one.

[mLuMaN83]

I wanted to bump this up. I bought another Climate Control unit off ebay, the new style one, and I hope this will fix my issue. I will keep you posted in case this helps anybody in the future if this is in fact the reason for the issue. This thing has my mind boggled!

Edit:
So far, I think this may have done it! It is blowing the correct air temps out of the correct selected vents. Time will tell but I have a feeling this fixed it. I hope this thread can help somebody in the future. I was perplexed for 2 years!

[mLuMaN83]

UPDATE: Problem NOT fixed. I was driving home on the highway today and BAM! Warm air out the vents. I am back to square 1. Anybody have any earthly idea why the AC will work beautifully then while driving, out of nowhere, goes warm? As stated above, if I turn off the car for a bit and start her back up, 50% of the time, the AC will work again. Possible compressor going bad? Fan? Switches? Sensors? Help!

[kayger12]

Spit balling here, but could it be a belt/tensioner issue?

After the car warms up, just enough thermal expansion for the belt to slip?

Cools back down, just enough contraction to grab and spin the compressor...

Just trying to throw ideas your way.

Sent from my SCH-I535 using Tapatalk 4

[3ZHP]

UPDATE: Problem NOT fixed. I was driving home on the highway today and BAM! Warm air out the vents. I am back to square 1. Anybody have any earthly idea why the AC will work beautifully then while driving, out of nowhere, goes warm? As stated above, if I turn off the car for a bit and start her back up, 50% of the time, the AC will work again. Possible compressor going bad? Fan? Switches? Sensors? Help!

Had that same problem this summer but haven't experienced it lately. I have changed my belts recently but, that was just a PM thing. Note: I did find other threads ou there about the situation so, It's not that uncommon.


Sent from my iPhone using Tapatalk

[telijah]

When it goes warm, check to see if the center of the compressor is still turning. If not, then it could be compressor or pressure switch issues. If it is still spinning, maybe it is an actual HVAC unit failure?

[ELCID86]

Any updates on this? I'm having warmer air out of the two passenger side vents.

[kayger12]

Any updates on this? I'm having warmer air out of the two passenger side vents.

That sounds like low refrigerant.

[ELCID86]

That's what I was thinking. New to me car. PO had it charged at 102k and evac/charge at 133k according to the records he gave me. I'm now at 138k. I wonder if they used dye.

[mLuMaN83]

Nope. Problem still exists with new climate control unit. Goes warm when it dam well pleases. It's like the little flaps in there quit working because if I change from say auto to defrost or to feet, I feel ice cold out the face vents for a seconds while the vents change position then back to warm...buuuut, still luke warm out the selected vent area. Once it goes warm, it stays that way until I shut the car off for a little bit, then its a 50/50 chance the AC will blow as it should. Wild wild.

I'm going to have to bring it in somewhere. I can't figure it out.