94 w124 Air Conditioning problem
 

On my 94 e320 my AC works moderately well if the car has been in the shade or other cool area but doesn't seem to be able to "catch up" with the heat and cool sufficiently if the car has been sitting in the sun. At low fan speed i can feel that the air coming out is cool but when the fan is on high (or auto) the air isn't cool at all. After about 30 or 40 minutes of driving around like the A/C is finally caught up and the car is cool. I would expect that it should only take about 5 or 10 minutes for the AC to feel cool on your face etc so i suspect that something isn't working properly. Where in the engine bay can I check the refrigerant level (where is the compressor?) Or is this likely a different issue.

http://image.inkfrog.com/pix/houstoninc/DSC04589.JPG

BTW: I read in a different post that all 94 cars had R134a - can anyone confirm this? If so, I should be able to recharge the system myself (if it is low that is).

You need a/c in Minn:eek:?

You may just be alittle low on r134 (yes it uses 134). I would insure that the electric fan in front of the condenser is coming on when it is supposed to too. Get some gauges on it and come back with the pressure readings/ambient temperature.

there is a sight glass behind the driver side headlight. look for bubbles.

If the system is 134, the sight glass can be very misleading. You need gauges to check 134 pressure.

hmm...so am i better off taking this to an A/C specialist or can i work on this system myself? I do virtually every other repair necessary on this car and our 190e so I'm fairly competent with a wrench. If I go to an auto parts store can I find the equipment to test my system pressure? I'll run the car with the AC on and check to make sure that the fans are engaging and the compressor is running. If i set the temp wheel at 65 and the fan on hi the compressor should run enough to kick the aux. fans in right? That should/would also tell me if the system was low on 134 (ie if the fans did not come on)

I was going to mention that if you had no gages..
usually, the aux fan should come on at ambient 75F at idle if there is enough refrigerant to trip the high side pressure sw... if not , try a little bit of rpms..
It is a good idea to jumper the fan high pressure sw first to be assured of the circuits integrity.. than you know it is pressure related [ vs electrical fan circuit] if it does not come on....
..just remember, the aux fandoes not always come on with a/c compressor on that model... it only comes on when there is a high heat load, and that takes at least 75F ambient to get accomplished..

wheres the high pressure sw to jumper to test out the aux fans. I suppose I can idle the car out in the heat (its been like 80 something here) with the AC on to see if the fans kick in. Do the aux fans have a temp threshold to come on as well? The 190e 2.3 had an engine block temp sensor for the aux fan that would trip the fan at like 87 or 90 degree C. Anything similar to that on the m104?

Thanks for the help!!

The aux fan does have a coolant temp sensor for high speed when coolant gets to 105C, BUT , that has NOTHING to do with the low fan curcuit, which is refrigerant a/c pressure activated. This sw is on the drier/reciever near the driver headlamp. It has a pigtail on it and you can jumper the feed wires ..that will [should] activate the LOW speed aux fan...which is what should happen under thermal heat load when there is enough freon/pressure on the systems high side [ condenser].. all the fan does is helps keep the high pressure in check at high load to aid in cooling and not let the pressure get so high that it kicks out the compressor...that is why it does not run all the time [ as in low thermal load conditions]

The confusion comes from many cars being wired to have fan on whenever a/c system is on .. not on this chassis..it is an AUXILLARY fan...meaning just that.

are you getting good air flow ?
 

Is it that the air flow is powerful but just not cold enough or could it be the air flow is not strong enough.

a wild card idea but I had the latter problem which turned out that some previous owner/tech had fitted the blower backwards which surprisingly gave reasonable air when stationary but very little on the move (as it was fighting the natural air flow). Turned the fan around and now I have lovely cold air :cool:

just an idea

Keith

What you describe could very well be a vacuum pod on the fresh air door not operating correctly. I would check the refrigerant level with manifold guages and a thermometer. If it appears to be somewhere near properly charged, your problem is then almost definitely a problem with the fresh air door. In really hot weather it should not be allowing fresh air until the cabin is cooled down really well.

Good luck,

According to my gauges, the low speed fans come on at about 250 psi on the highside, and turn off around 180-190 psi. NOTE: I have R-12 . If the ac worked before and now it cant "hold a thermal load" or in other words cant keep up, its probably just low on freon.

Don't forget to check if the low-speed aux fan resistor is working as well. Mine was shot, with crappy A/C as a symptom. On the E420 it took a while to replace - hard to get to, but the 300E should have a bit more space for working on it. i think the part was $40. Mine was corroded and obviously burnt.

troy
1995 E420 95k

Whether the aux fan works or not will have little to do with ac performance and capacity. That is NOT to say you should not worry about the aux fan working properly. It's purpose is to bring down dangerous high side pressure for system protection, thus it is very important.

Have a great day,

thanks for all the suggestions, i'll have to check out the aux fans and find some tools to check the pressure of the system. I know that the blower is installed correctly as there is plenty of air flow its just not cool enough. About the vacuum pod on the fresh air door, when i start the car i hear this vent somewhere under the dash move (i can't tell if its open or close) is this normal? I suspect that this fresh air door could be the culprit, but who knows.

ok, so what sort of pressure gauges do i need to check the pressure in the system and where could i buy these gauges?

Also, once I get the gauges where do i check the pressure? Thanks!!!

I'll attempt to measure the temperature of the air at some point and post the readings.

www.harbourfreight.com (probably a store near you)
has 134a gauges with three hoses starting at $39.95. Get a long digital thermometer and keep it stuck in the middle vent. Look for 41-48 degree vent temps at 80-85 degree Min weather.

The gauges-red goes to high side (going from compressor to condenser), blue goes to low side. (dryer can to firewall).

Today I took my car to a shop and had them do an AC-check up. They told me that the car had 1.1lbs of refridgerant in the system and that capacity was 2.2lbs. Therefore they would have to evacuate the system and recharge it. They quoted me 69.90 for the service and then about 70 or 80 more for the refrigerant (and oil) at 35.00/lb. I obviously said no to this and was hoping you guys could help me do this on my own. The car is a 94 E320 and should take r134a refrig.

Can I DIY this one (for under $150) and what do I need? (refidgerant, etc.)

.. well , seeing you know there is still over a lb pf refrigerant and you are not wanting to spend to do it up the best way.. you can just add 1 can of 134 and that should top it enough to get you going..
Not the best, but usually when there is still a decent amount left in a system, the leak is to the outside , ] usually high side] so moisture is not usually a problem and you can get away with a top off..
taking a chance , mind you...but it has worked in many many cases..

You know the proper way, but sometimes finance dictates..

Do not add more than 1 can til you see where you are at..and of that is suuficient , leave well enough alone

For the a/c guys .. yeah , I know ..but ....

Where on the car do I put the new refridg? I am a complete newb to AC systems (as you can probably tell). Is 150 a reasonable price to pay? Does anyone know of a reputable AC shop in south eastern minnesota (i live in rochester)

See attached thumb -> is this the port?

...It is , but if you are not hip to this stuff, give it to someone who is willing to top it off for you.

As in...take it to a shop :) Thats probably what I'll end up doing. I just wanted a fair price and a reputable shop.

$35 a lb for R134 seems way high.... I've heard it's been going up, but $35 a lb?
You might want to look for a dedicated AC service place, preferably one that advertises 19.99 refills :)
There is one locally (ok, Allentown PA) that had a 300D parked there a lot, assuming it was either an owner or an employee....
I had my indy shop fix the 300SD's AC a while back and it cost about $400... and I think the R12 was around $48 a lb...

You can get R12 gauges at the local supply hose that caters to the commercial/residential heating and air conditioning trade.

Good luck,

Sorry, but I don't see how R12 gauges would help me, since the car is R134a.

Your right smarty pants your 1994 car is factory R134a, as mentioned above go to harbour freight, northern tool, ect...and get some R134a manifold gauges! Starting at $39. Or your tightness can go to Autozone and rent them for free, while there get the $8.99 DVD or go ahead and pay the shop. For what they charge you can get gauges ect....12oz 134a is $10 at Autozone vs there $30?

w124 air Cond.
 

You can buy the gages at almost any auto parts supply house. You said that this is a 134 system? If so the high and pressure taps are designed so that you can't reverse them the low pressure tap is at the suction of the compressor (between the compressor and the evaporator. the high pressure tap is at the discharge of the condenser. The pressures are available from the dealer. I'm more familiar with R12.


Another possible cause for low rpm capacity reduction is worn compressor reed valves. I have a similar problem to yours. Mine was dignosed as worn reeds. Mine will cool down to a liveable level in abouit 10 minutes. I have no problems at >20mph after initial coldown.

To correctly evacuate the system I would need to rent a vacuum pump, but what is the procedure for this? I didn't mean to sound smart, I obviously need help if i'm going to do this myself. I called a few other shops today and the price was about the same everywhere. I found r134 as low as $20/lb but then their evac. and recharge fee was higher (so the total came out the same). I'll check out the local auto shops tonight and see if theres a set of gauges and a DVD that I can rent/buy to preform the recharge myself. I'm interesting in learning to do this the right way, I just need help. Thanks!!

renting a vacuum pump is going to be a waste of money. It will cost you more to rent one and refill the system yourself since if you evacuate the system you are going to need approximately 3 cans or 134. The way I see it if you want to do it the cheap way add a can of refrigerant and see what happens. If not it would be economically more viable to have the shop do it. On the other hand if you want to do it yourself, you see yourself doing this again and you don't mind investing in tools then purchase a pump and gauges and your good to go.

So if i bought this:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92475
(vacuum pump)

and these:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=2435
(R134 gauges)

I could do this myself. I am not confident with the general procedure, what are the steps to evacuate and then recharge. Reading the manual for the vacuum pump it tells you to attach the vacuum line to the vacuum port on the A/C system. Where is this located?

Not to upset the party, but this is what you should be buying before anything... I can see by your postings/questions that you are in dire need of some basics before continuing and have a feeling you are going to get youtself into trouble.

Autozone/ $8.99 AC repair DVD by Bruce Bone......
Do it...

skiier, you did good on the gauges but the vacuum pump is the venturi type (do a search on this forum under venturi). this will not pull a deep enough vac and the air compressor needed to drive it continuously would have to be huge. this was just discussed the other day on this forum and other numerous times.

As stated, go to Auto Zone and get the Bruce Boneback AC DVD $8 to get confident, they will also rent you the correct electrical, rotary vane vacuum pump free, you get your full depsit back when you return it. Also get the 5" vent thermometer while there.

Ok, I'll stop by the local Autozone and pick up a copy of that DVD this afternoon. Thanks for the suggestions

Correct me if i'm wrong but I have been unable to locate any Autozone which loans out this type of vacuum pump or for that matter a gauge set.

I'll check with them when i go there and let you know. I haven't heard anyone saying that they loan out the gauges, thats why people suggest buying them on harborfreight.com

Do not call, go by the biggest busiest store, ask manager for a rotary vane evacuation pump. I went to 3 autozones, all regular employees said they did not, 1 brought out the mity vac hand pump, but the manager went to the back and brought out the Mastercool 2 CFM pump that nobaody else knew about!

As far as gauges I would just buy my own, skiier just got a new set from harbour freight for $39!

$39 is only for the R12 gauges, the R134 gauges are 49.99 and up.

I paid $99 for my Autozone crappy Interdynamics 134a set! That Harbour Freight set looks alot nicer than mine. I did get a nice old all brass Robinair R12/22 set from a co-workers deceased dad for $30. Did not know about Harbour Freight or Northern Tools at the time. If you can wait ebay has some deals especially for r12 gauges. Search under Robinair, Ritchie Yellow Jacket, Mastercool, snap on, or just do a R12/22 or R134a manifold gauge set search, Check local pawn shops and used tool stores also. But $39 and $49 new, I would run to Harbour Freight.

DIY Residential-Home HVAC (A/C) Anyone?

Check the General Discussion forum for this topic I started. Alot of these tools, fundamentals, service and diag that we are acquiring can be used for home systems also.

James do you have the paperwork from when you rented the pump. The reason I ask is that the emplyees at autozone that I talked to insisted they did not in fact have a vacuum pump and that all the stores carry the exact same tools for the loaner program. Unfortunately there is nothing listed on their web site so I had no foot to stand on but if I could get a reference number that may help.

I have not rented the pump yet, I have to figure out what brand new or rebuilt of R4 compressor to get first and what vendor.

The Vacuum pump at AutoZone is for sale also at $199. The mgr pulled it up on the store computer to show some other employee. The screen had the number and the price $199. 2 CFM Mastercool single phase evacuation pump.
She brought the big opened box out. She said no one had rented it yet.

When i rent it i will save the paperwork and post it here.

Thanks James. In the meanwhile I just wrote their customer service department to see what they have to say.

In their automotive A/C video it says that *most* Autozone locations rent the tools needed like gauges, vacuum pump, etc. I'd ask to talk to a manager like James L suggested.

I put gauges on my 1993, W124, OE 134A car yesterday for evaluation. It has been cooling good but wanted to check to aide your 1994 and see if it is under charged, overcharged or any air in the lines? Here are my parameters:

Ambient (outside air) 82-85F, Humidity 40-45%, Shade, 11:00 am:

engine off (cold): low side 90 psi - high side 90 psi
engine on, a/c on: low side 30 psi - high side 195 psi

aux fan comes on: low side 20 psi - high side 245 psi
(takes it back to 30/190)

bridge for aux fan on all time: low side 30 psi - high side 190-200 psi

center dash vent 41F

engine off (hot): low side 55 psi - high side 125 psi

no bubbles or foam in sight glass at any time or test, system has yellow dye in it and no visible leaks anywhere or in evap drain!

My system is cooling good and I am getting low dash vent temps (have had thermometer in dash all week) but I feel it may be slightly undercharged?
Also 2 years ago a tech put 1/2 a 12oz 134a can in with low side suicide hose and up/down roation of can. (before I knew better). I wonder if it would be good to discarge, evacuate and recharge? How do I know if any air or moisture is in the system? I will probably leave the sytem alone since it is cooling good but the 95F + days have not arrived yet!

Advise and opinions sought and wellcomed

Recycled
 

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