1990 190E 2.6 A/C - PeachParts Mercedes-Benz Forum

lsmalley · #1 06-04-2010, 04:41 AM

anyone familiar with the a/c system of the above mentioned car? i checked other posts, but all lead to a dead end. My first problem is that my auxillary fans are not working when my a/c is on, but when my temp increases to about 115 C then the high speed aux fans will come on. I'm not sure if the aux fans has anything to do with the temp or coolness of the a/c, but i did disconnect the switch on top of the valve body and the aux fans stayed on high speed until i shut it off or reconnected, but the temp didn't get any cooler. Second, the a/c does not cool at all if im at a stand still or just idling, in fact the air that comes out is hot, but once i drive and hit about 30 mph the air slowly begins to cool, but not really cold, only around 72-74 degrees.....i live where the summer temps are around 115+ F for summer. Third, whener i drive, even if the a/c is off, there is hot air coming from the side vents and defroster.....however once the a/c is engaged, the air come from the aforementioned locations will cool. Any help would be greatly appreciated. I had a complete a/c overhaul in april of 2008 where it was converted to r134 which i understand to be not as cool as r12, but i sat in a friends ford fusion today for 45 mins idle while he was at the dmv and his r134 worked a hell of a lot better than mine. suggestions or comments would be great, thanks guys

Cal Learner · #2 06-04-2010, 07:11 AM

It may be that you have a low refrigerant charge. That would explain both the inefficient cooling of the A/C system and the failure of the aux fans to engage when the A/C is running. Pressure testing will give you the answer. You may also have a bad monovalve causing heat to come out of your vents.

d.delano · #3 06-04-2010, 11:38 AM

I have the same hot air coming out of the side vents and windshield vent, but only while sitting in traffic or climbing a long steep hill. Otherwise the AC works fine, and the fans come on when they should. Is this the monovalve http://catalog.peachparts.com/ShopByVehicle.epc?q=1993-Mercedes--Benz-190e--.6-Climate--Control&yearid=1993%40%401993&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6132%3AMBC%7C1486%3AED%7C10000011%3ASM%7C847%40%40190E+2%2E6&catid=242213%40%40Climate+Control&subcatid=242325@@Heater+Valve&mode=PA

if so, where is it located and how hard is it to change out? thanks

mbzman · #4 06-04-2010, 01:09 PM

Check you system pressure to confirm you have an adequate charge. Newer vehicles will cool better because they were designed to run on R134A. They will have larger condensers and more efficient compressors that will yield better results. Your car will never have as good a performance with R134A as it was originally designed for R12. What was changed when you had the A/C serviced in 2008?

lsmalley · #5 06-04-2010, 01:34 PM

i changed the heater valve behind the firewall on the passenger side myself less than 6 months ago, but when i had my a/c converted the following was done: r134 service valves (high side, low side valves), receiver dryer replaced, a/c compressor replaced, smog pump replaced and alternator replaced, bearing bracket also replaced. more suggestions or comments?

tjts1 · #6 06-04-2010, 02:15 PM

Refill it with duracool. It will run much colder.

lsmalley · #7 06-08-2010, 05:58 AM

I'm So glad I didn't go to that guy that was trying to charge me $135 to recharge my a/c.....after taking out my glove box and not knowing what the hell I was doing, I decided to take a simpler approach (thanks to slk230red) i went to have a look at my heater/ac valve just next to the battery behind the firewall and under the screen. I just replaced it 11/5/09 (i keep detailed records on everything i replace and the mileage). i disconnected the valve and lifted the little lever up and blew inside WALLAH! the air went straight through it. So i filled my mouth with coolant (just kidding), i used regular water and blew it through both ends with the levber up and it wasn't blocking out the flow of water. I then plugged both ends of the valve and reconnected it and m,y a/c doesn't blow hot/cold air anymore and my ac will stay cool even if i sit idle or accelerate. My question is, how long are these partsd supposed to last? Its made out of all plastic but wow, only 7 months? and i think it actually went out before then so maybe 4 months. was it a defective part? also here is a detailed link with pics on how to trouble shhot the a/c system for the 190 http://www.benzworld.org/forums/w201-190-class/1358590-troubleshooting-mercedes-benz-190-e-d.html

#8 06-08-2010, 07:16 AM

Quote:

Originally Posted by tjts1

Refill it with duracool. It will run much colder.

If you're going to suggest the use of junk refrigerant, the responsible thing to do would be to point out that the system should be properly labeled and duracool fittings used. If this is not done it is not only a violation of Federal Law but more importantly could easily lead to an unsuspecting recovery machine owner contaminating an entire vessel of legitimate refrigerant.

tjts1 · #9 06-08-2010, 10:29 AM

Quote:

Originally Posted by LarryBible

If you're going to suggest the use of junk refrigerant, the responsible thing to do would be to point out that the system should be properly labeled and duracool fittings used. If this is not done it is not only a violation of Federal Law but more importantly could easily lead to an unsuspecting recovery machine owner contaminating an entire vessel of legitimate refrigerant.

Oh get over yourself. The only 'junk' is R134 conversions where the vents have the cooling power of an asthmatic mouse. All the labeling is in the kit.

#10 06-08-2010, 10:54 AM

Quote:

Originally Posted by tjts1

Oh get over yourself. The only 'junk' is R134 conversions where the vents have the cooling power of an asthmatic mouse. All the labeling is in the kit.

Are the correct fittings ALSO in this kit? Labeling alone does not satisfy Federal Law. Junk refrigerants or ANY refrigerant must have the proper fittings to comply with Federal Law.

I do not refer to Junk refrigerants as JUNK refrigerants based on their ability to make or not make cold air. They are JUNK refrigerants because of the fact that they COMMONLY cause tanks full of recovered refrigerant to be contaminated. If the day were to come when YOU had to suffer the loss of a tank full of legitimate refrigerant AND pay a disposal fee on top of that, then YOU would be calling them JUNK TOO!

BTW, the best way to make converted 134 systems cool properly is to not convert them in the first place or reverse convert them if they have already suffered such fate. R12 costs very little more than the JUNK, cools properly and will not wreck a tankful of recovered refrigerant. As an added bonus, R12 is not a blend requiring complete recharge in the case of a leak or a flammable which is illegal in 18 states.

mbzman · #11 06-08-2010, 01:12 PM

I agree with Larry on aftermarket refrigerant blends. If your car has already been converted to R134A and is working satisfactorily then leave it alone. If you have a leak or breakdown in the future where you would need to evacuate the system then you might want to consider going back to R12. Either way, only stick to R12 or R134A.

lsmalley · #12 06-09-2010, 01:28 AM

ok so someone mentioned to me about evacuating whatever is in my a/c, they said it takes about an hour, and then they said they would need to recharge it with 2 lbs of freon (or whatever it is, r134), it was a random mechanic i went to. is this the correct procedure to do in order to get the car cooling again? thanks guys

mbzman · #13 06-09-2010, 02:13 AM

It is very possible that you have a leak in the system. You really need to have a proper diagnosis performed before you refill it. No point in charging a system that does not hold pressure. It really depends on how well the conversion to R134A was done. Usually ones that were not performed with shortcuts will usually result in marginal results or a component failure. As well, it sounds as though the heater valve may be acting up. You may want to do a search to see if you can carry out more tests on it.

lsmalley · #14 06-09-2010, 03:52 AM

mbzman- i just got home from driving around for 45 min to an hour. the heater valve was not holding back the coolant from flowing so i plugged it up. the a/c seems to be only from the a/c now and not a mixture of heat from defrost and side vents. i went out and sat with the car idling and the ac seems to be fine since i did that; even when i accelerate no heat comes out and its working fine now.....BUT, its nighttime now and the temp is only 81 degrees, usually when its during the day and the temp is at 109 degrees it feels like the a/c is not cooling. also, i made a discovery while i was driving...i noticed my aux fans did not turn on low speed. could this be a main part of the problem? i read several other threads and people seem to speak about jumpering(?) two pig tail wires. i have no i dea what that means so i ordered the following pieces of equipment: AC/Refrigerant Temperature Sensor; Auxiliary Fan Switch at Receiver Drier, AC Cutoff Switch; On Cylinder Head; Blue Insulator with 2 Prong Connector; 130 Degree C, Air Temperature Sensor/Thermostat. I plan on replacing them all weather they work or not because i can't tell and i am a beginner when it comes to automechanics, but i can't afford to spend $$$$$ for something that i can learn how to do myself. what is the main thing that actually controls the aux fans and tells them to turn on low speed? because i know if i unplug the blue two-prong adapter thing on top of the valve the aux fans kick in high speed. please advise and thanks for your time.

Cal Learner · #15 06-09-2010, 07:59 AM

Lsmalley, most of us understand your exasperation with the A/C systems from 20 years ago, particularly if they've been converted to R134A. The photo below shows the drier/receiver with its high pressure switch. The pigtails come off the high pressure switch to activate the aux fans on low speed. If your fans do not engage at low speed, the most likely causes are: (1) low refrigerant pressure as I mentioned in my earlier post above; (2) bad pressure switch; (3) bad dropping resistor; or (4) bad fan relay. You know that the fan motors and wiring are good, you proved that when you disconnected the blue base temp sensor and got high fan speed. It's the same circuit for both fan speeds, except for the resistor and the relay. The pigtail jumpering test helps confirm the rest of the low fan circuit, except for the switch itself. The pigtails are normally covered by plastic sleeves (as shown in the photo), but yours may not have the sleeves through wear and aging. The test is to slide the sleeves back and touch the wires to each other (KOEO). That should trigger low fan. If no, there's an upstream problem, probably the relay or the resistor. If yes, it's likely the switch is toast.