Has anyone service their own A/C? I am the third owner of an 86 420sel. It looks like this car had A/C service three times in the last two years (as recently last year). Now it is not cold again. There must be a leak somewhere. I look at the hoses of the A/C system and saw that the ones from the drier to the condenser and the condenser to the compressor having gunk on them. I think this is the source of the leak. It there a good source to learn to diy or should I keep paying the mechanic to fix this? Is there a lot of equipment to buy? I am fairly technically competent and can learn very quickly.

Thanks,

John

I know one person who services their own AC. They invested in a vac pump and a couple of special gauges and a leak detector. The latter item is now fairly inexpensive.
There are good serviceable items available for not too many $$
see: http://www.thetoolwarehouse.net/
My friend studied the subject like he flies his aircraft, taking notes and planning the steps thoroughly before attemptingto set out. You have to flush the whole system, that is an important step if your A/C has been contaminated or up to air for a long time. New compressors can crud up a system to the point it is full of "black death" from the Teflon blades in the compressor that turn to crud. Older compressors will not do this, so knowing exactly what you have is crutial. The choice of flushing additives is debatable, I believe he used Acetone at one point followed by somestuff that removes water. What oil to use is also something to be studied. There is too much on this subject for me to keep up with, I let an A/C shop do it. I dropped $1400 on new hoses, a new dryer, expansion valve and a recharge with R12. It still blows cold 3 or 4 years later so I am happy.

We don't have enough info to help you well.
Were your AC services based on definite leaks? Where were the leaks and were theygross leaks or minor leaks? What did the shop use for leak detectors, dye or sniffers? (Some say dye is corrosive).

Did the shop install new fittings on existing hoses, or new hoses and were they OE hoses or aftermarket hoses?
At the price of refrigerant gas there is no substitute for new hoses that should keep pressure for maybe another decade if the pump, expansion valve and so on are new.
Also, I suggest one avoid conversion to R134A unless that has already been done. Now, are up to this kind of job?

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Use the search function: One of your members, Larry Bible does his own AC service and has some very specific recommendations, tips and opinions.

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Yeah, tell Larry you're going to mix some Duracool with r12 heh heh

__________________
Current Crop:
2002 ML500
1997 SL600
1969 Corvette (for sale, perfect shape)
1984 RX7 GSLSE

Wanted:
a diesel MB!
Looking for a new SL.

A good place to start on A/C education is www.ackits.com they have a forum and several articals on A/C repair. R12 vs R134 and they sell the equipment needed to do the job.

Hi,

Unless you alreadyb have the vacuum pump and gauges and an ample supply of r12, it's probably best to get it fixed at a reputable shop. The gauges, pump, and freon would probably cost you 50% to 100% of what it costs to do the job. You also need a leak detector, but could skip it if you were sure of where the leak was or used some sort of dye to identify or got a diagnosis at a shop and then did the fix work yourself.

Steve

Steve, a lot of us look conversely at buying the tools. It may cost as much as a farmed-out job, but then you have the tools for any future a/c work. Since John is a DIYer, he may be wise to buy his own tools. They'll pay for themselves on the first job.

Although staying with r12 gives superior cooling, a good conversion to r134 may be more appealing for the DIYer and 'good enough' if you live in the northern climates with mild summers. The two cars I converted keep my family cool.

By getting creative you can save some of the tool money by making a vacuum pump out of an old refrigerator compressor, or in my case I have access to a good portable industrial vacuum pump.

I taught myself a/c repair simply by spending a lot of time reading posts on aircondition.com and ackits.com.

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95 E320 Cabriolet, 159K

I did this job not too long ago on a Q45.... it was sort of a hybrid of me and the shop...

I did all of the work... and then took it to them to "pull a vacuum" and to install the cooling product.

As a 300e owner.... I decided not to purchase a car unless it had the A/C re-done.

I know if you have a pre-existing situation that would be impossible. If I had a 300e and it needed A/C work..I would do it myself..because no job should be done without going after the evaoporator... and I am told that is a 12 hour job... leaving it to a professional would be cost prohibitive..

I have receipts totaling 2900 for compressor, drier, the a/c manifold hose, evaporator/expansion valve... so it is involved.

If you have a 190e, I understand you can get to the evaporator through the firewall...much better design.

Let's not get the cart in front of the horse. There is no need to replace the evaporator unless it is diagnosed as having a leak. Even though the ones in the 124 cars are prone to leak, they are not DESTINED to leak. Mine is an '88 model and still doesn't leak (knock on wood.)

Doing a/c work involves MUCH more than just laying out some money for the necessary tools and equipment. You need to read and study thoroughly not only the concepts, but the diagnostic and service procedures. I've been around automotive a/c service since I was seven years old and that was almost 50 years ago. My Dad started doing auto a/c work in 1956 or 1957.

I am always one to encourage DIY, but in the case of a/c service you not only need to look before you leap, but study hard before you leap.

BTW, if you have a bad hose, you can go to any a/c shop and they can replace the rubber part of the hose using your fittings. All you have to do is take them the hose. It's not very expensive to have a hose redone. New hoses are EXPEN$IVE!

Good luck,

if i had a bad a/c system and the evaporator was 17 years old...I think I would add that to my list of parts needed.

from what I have seen over the years..only the condensers hold up...and of course they are about the easiest part to access.....

I think the biggest mistake we all make is not replacing the driers every 5-6 years since they remove the deadly moisture from the systemm..

just my thoughts... I am far from an expert.....

I used to service my own AC when R-12 was 99cents a can but now it is expensive and there are environmental issues. I can't afford to take the risk. I found an AC shop that will suck all of your freon out and let you drive it home and replace any parts necessary. They will also do a discharge and recharge if you don't need A/C work but have to remove your compressor to fix other stuff on your car.
When you bring it back they charge you a flat rate for recharge plus the additional freon you need over what they sucked out. They are honest about that too. It saves me enough money to justify replacing everything that might reed replacing so I don't cut corners which would cause the job to go bad on me later. It also assures me that the system is recharged properly and leak tested.
They have all of the business they can handle and the recharge is the quickest, cleanest and most profitable job they do so it works out well for everyone. They get parts wholesale and sell them to me at retail (which I would pay for them anyway) so they make a parts profit on the deal too.
I would suggest dropping in on a few A/C shops in your area to see if you can find a similar deal.

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Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL

This is the first I've heard of somebody using this practise. Driers are replaced only if the system is breached. A/C systems should be left alone until something goes wrong. They are sealed systems and there should be no moisture in the system except what was introduced during installation. Except for running the a/c every once in a while during the cold season and cleaning debris from the condenser, there is no preventive maintenance or scheduled service that can be done to an a/c system.

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95 E320 Cabriolet, 159K

Perhaps I am wrong about the drier.... but an a/c guy once told me that no matter how sealed the system is, small molecules get in, and small ones get out....

and the dessicant (spelling?) the drying agent gets used up.... at what rate I don't know... I have never changed out a drier just for the sake of doing one.....

I am told it is moisture that ruins things like the evaporator... of course at some point the hoses will disintegrate...and the mechanics of a compressor will fail.

maybe we need an A/C guy to weigh in....

otherwise, what would you need the drier for in the first place?

I have replaced major components on my old 450SL (compressor, evaporator, receiver/dryer), my Porsche (compressor, receiver/dryer), and my Ferrari (receiver/dry/pressure switch). There is no magic to it, and it is not rocket science (merely thermodynamics). I've used an alternative refrigerant in my 450SL since 1994, and in my Porsche since 1997 when I replaced the Nippon compressor with a Sanden. There is no problem with alternate refrigerants as evidenced by the length of time I've used them in two cars. They are flammable but you only use about 1/2 as much on a per pound basis meaning you only have about one pound in the system. And besides, there is a whole lot more gasoline in a vehicle than there is refrigerant.

Purchase a new compressor, not a rebuilt one if you have to replace a compressor. Pulling a vacuum on a system is not as important if you use an alternate refrigerant.

Never had any problem with my 400E and SLK so I cannot comment about 134 work.

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Lawrence Coppari

2002 SLK32 AMG
2005 Acura TL
1987 328GTS
1986 944T

The dessicant in the drier removes moisture from the system so that it doesn't mix with the freon and form hydrofluoric acid which eats up the evaporator. Right?

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Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL