A/C ineffective above 90 degrees outside

[jbach36]

I had my W124 recharged last year. The mechanic added (?) R134 to the R12, I think it was. He said that the 2 of them together, get colder than either one can achieve on its own. When he was done, the a/c wasn't great, but better than it'd ever been.

My experience with a/c on 2 different Benz's I owned, is that they simply made (or bought from another manufacturer), a really, really crummy a/c system. It's my estimation, that they're adequate, at best, so long as it doesn't get real hot out. That's why you see a lot of older Benz's, and BMW's, with tinted windows.

I live in the south, and it gets a mite toasty down here. When the temp is 87, like even just a week ago, it can cool the car down within reason after maybe 3 or 4 minutes. But today was 91, plus the car was sitting in the sun for a few hours (the heat builds up in the seats, dash, etc.), and even after 1/2 hour of driving, some of it at 65 mph, with the fan on high, and recirculate on, it never cooled the car down properly.

My guess is that the a/c is simply doing, all it was designed to do,and above a certain temperature, say 90, it just ....can't handle it . Their a/c systems weren't made right to begin with. One Mercedes mechanic told me the problem with their systems is that the (?) evaporator or the coils, are simply too small; it simply can't get rid of too much heat.

1) What's your take on this scenario? Anyone from the south here who has a Benz that cools well in this August heat?

2) Who made the a/c units for Benz? I heard they were American made AC Delco.

3) Where were the a/c's put on the cars? I talked to one guy who swore that any a/c units, were added on to the car when it arrived in the US, zero were put on in the factory, a claim I doubt.

4) What do you all think about that 'new' freon that says something like "13 degrees colder than R12" on the can? Anyone tried it, and is it any good?

1991 300d, 163,000

[sjh]

Here's a quick comment. There are quite a few A/C threads and experienced people so you should get some answers.

I was driving out of Sacramento last week, heading towards the bay.

The outside temp read 91. The A/C was on max. It's worked well since I've had it. The car could not get cool enough.

I kept driving. Hit Vacaville. Temp still read 91. Car was very comfortable.

It's not just the ambient temp but radiant from sun and probably humidity that affect life inside the coach.

If I lived in a high radiant environment I'd look into a quality tint for my car.

.

[sixto]

Originally Posted by jbach36

1) What's your take on this scenario? Anyone from the south here who has a Benz that cools well in this August heat?

2) Who made the a/c units for Benz? I heard they were American made AC Delco.

3) Where were the a/c's put on the cars? I talked to one guy who swore that any a/c units, were added on to the car when it arrived in the US, zero were put on in the factory, a claim I doubt.

1) Whole bunch of members from Florida to Texas enjoying straight R-12. Make sure your clutch and auxiliary fans are working.

2) Mid-70s to early-80s MB used a Chrysler designed automatic climate control system. Many used GM compressors through 1985. Mostly Bosch systems with Nipponsdenso compressors since.

3) That might have been true through the early-70s. Probably continued into the mid-70s for W115s. Into the 80s for gray market and private imports.

I don't think it's fair to say that the AC system is inadequate by design. Otherwise, no one would pay $40-80K for these cars when new, and I'm sure a good number were sold new wherever you are. 20-30 years later there is an accumulation of dirt on the condensers and evaporators that significantly reduces the AC systems' ability to cool. Check the AC sticky thread for some ideas.

It's up to you whether to post again that your mechanic mixed R-12 and R-134a. You probably won't get any useful discussion if that's your opening line

Sixto
87 300D

[Manual Life]

I'v been in 100+ temps for a couple months now. My a/c works like this.

At a stop and in traffic, much better than outside but not cold.

Over 30mph, cold.

However, when I am driving 10+ miles and the a/c is cold it's still not enough to cool the interior completely because the heat coming in from outside is so strong.

I didn't answer your questions.

[okto]

The first step in fixing your AC is never to let that mechanic touch your car again.

R12 and R134 do NOT mix. They don't even work in the same hardware.

[vstech]

Originally Posted by okto

The first step in fixing your AC is never to let that mechanic touch your car again.

R12 and R134 do NOT mix. They don't even work in the same hardware.

False.

It's NOT a good practice, but 134 and R12 mixed in correct portions will produce an interesting mix of good and adequate performance... while the mix is correct... there are several wikki articles about the practice. some mechanics will attempt this, but it's certainly not wise. first off, the low 12 leaked out somehow, so it will continue to, and the 134 is a smaller molecule, so it will leak out as well, but in different portions.
so the first time you get it it may work great, then the gasses leak out, and you have an lower concentration of one vs the other, then it gets recharged, and you now have improper oil circulation, and other issues causing problems.
the practice is generally done to save the money of a flush and fill with ester oil, because the 12 still in the system will circulate with the 134, and carry the mineral oil that the 134 cannot move...
it's NOT wise, but it CAN work. the problem lies in how long it will work, and how the mechanic knows the mix of 12 will be adequate to carry the oil...

OP, properly CLEANED and charged, the a/c in the 123's and 126's are decent even at around 105F sunny days.
with the proper R12 refrigerant in a leak free system.

[ds190]

Originally Posted by vstech

the practice is generally done to save the money of a flush and fill with ester oil, because the 12 still in the system will circulate with the 134, and carry the mineral oil that the 134 cannot move...

So then, ester oil is OK with both R12 and r134?

Is PAG oil OK with only r134, or with both as well?

Thanks VStech.

[pj67coll]

Originally Posted by jbach36

1) What's your take on this scenario? Anyone from the south here who has a Benz that cools well in this August heat?

I live in Phoenix where you will find most older Benz's 70-s thru 90's driving around with their windows down. The AC's have almost all failed.

2) Who made the a/c units for Benz? I heard they were American made AC Delco.

It was a Chrysler design, at least the control modules were. A travesty of monumental proportions. Mercedes were trying to be too clever by half and as such incorporated one of the worst pieces of over-designed under-engineered junk ever into their cars.

Interestingly the number of W140's I've seen driving around here with their windows down indicates to me that Mercedes have some mental block when it comes to designing decent A/C systems.

3) Where were the a/c's put on the cars? I talked to one guy who swore that any a/c units, were added on to the car when it arrived in the US, zero were put on in the factory, a claim I doubt.

That is nonsense. Most US bound cars were factory equipped with A/C from the 70's on.

4) What do you all think about that 'new' freon that says something like "13 degrees colder than R12" on the can? Anyone tried it, and is it any good?

My opinion (and it's worth nothing more than that) is that that's just marketing hype.

Again in my opinion, the nature of A/C systems and the way Mercedes implemented them means that anyone who owns an older Benz and wants their cars A/C to cool decently will have to be prepared to spend a lot of time and money to completely remove, overhaul, rebuild, refit, re-engineer, re-whatever the entire system from the condenser out front to the controls in the dash and everything in between.

- Peter.

[engatwork]

You must not be too far south or your ambients would be higher than what you reported.

The best thing you could do for the car would be to open everything up, flush, button everything up with the proper oil fill, vacuum and charge with r12 like the car was designed to operate on.

Another option, and I have never looked into this, would be to install a 1995 E320/300 condenser in the earlier car and try it with 134. Not sure if the expansion valves are different between the two.

[tangofox007]

Originally Posted by jbach36

Who made the a/c units for Benz? I heard they were American made AC Delco.

Which of the numerous a/c system components is the "unit?"

[Brian Carlton]

It would be very beneficial for anyone who has an issue with the a/c to break down and spend the $5.00 for a vent thermometer. The device has a shaft that is stuck into the airstream and the face of the gauge sits at the outlet of the center vents.

Only when such data is available can a valid opinion be made as to the functionality of the system.

I've been watching the gauge on the SD recently since it's been recharged with 134 (without evac) and it will immediately get to 60F. after about two minutes. After running at over 2000 rpm for the next 10 minutes, it will gradually decline to about 47F. It will not go below this temperature but will hold 47F. until the cabin reaches the desired temperature of 20C. At that point, it will climb up to about 60F. and then gradually return to 47F. where the process repeats itself.

This performance is perfectly adequate for any ambient up to about 90F. in direct sunlight. Above this temperature will result in some challenge in reaching 20C. inside the cabin and the blower speed will not reduce.

I have not investigated whether the system is limited to 47F. due to the ETS. It is entirely possible that the ETS won't allow the system to go below this temperature due to the potential freezing of the evaporator. It's my suspicion that the performance of these vehicles could be improved markedly if an ETS could be sourced that would allow the evaporator to get very close to 32F. without freezing. However, the tolerances in the device probably won't allow this. There was a thread by Dave that discussed how to put a resistor in the ETS line to ease the point of opening closer to the evaporator freezing point. I think it bears further discussion.

[jbach36]

I have a temp gun, I'll try that tomorrow to get a temp read.

I can't believe your a/c puts out 47 degrees????? Yow baby!! That's cold! I doubt mine puts that out. Just guessing mine might put out 65 degrees when it's 87. Today was 87 and it wasn't that hard to cool the car. Yesterday at 91 degrees, it fell flat on its face.

[vstech]

My 126 with 12 puts out 34F... when it was working. my compressor failed... actually, it still works, but it keeps burning belts... it was old, I have since purchased new EVERYTHING except the evaporator coil, and will be cleaning it. I have disabled the ets in my 126. I know this leaves the evap with the possibility of freezing, but when it's 400F outside, I need my car a/c to WORK
I'd not recommend disabling the ETS to the average driver, but I monitor the temps with my left hand, and if it's too cold, I switch to economy.

[Brian Carlton]

Originally Posted by vstech

I have disabled the ets in my 126. I know this leaves the evap with the possibility of freezing, but when it's 400F outside, I need my car a/c to WORK
I'd not recommend disabling the ETS to the average driver, but I monitor the temps with my left hand, and if it's too cold, I switch to economy.

The second generation 126 will definitely freeze the evaporator with the Nippondenso compressor at any ambient below 95F. with R-134. That compressor and the better condenser on the second generation are a world of difference better than the R-4 and the smaller condenser on the original 126.

When you have 28F. vent temperatures for 30 minutes and you slowly watch it climb up to 55F............it's time to shut the system down for awhile............

[vstech]

I bet!