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1998 300TE
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6 Posts
Discussion Starter #1 (Edited)
I'm the second owner of an '89 300TE that had the AC changed to 134a, and the thing is not "cold". I can recharge the unit myself but I'm not sure of the maximum pressure (psi).

The pressure gauge on my 134a recharge kit (which I've used in the past to recharge two other non-MB cars) shows the high side of "filled" at 45psi. I topped-off the 134a in the MB to 45psi and it still isn't "cold" rather it is only "cool".

I know that 134a will never be as cold as 12 but the vehicle was already converted and I want to verify the maximum psi before going any further with this recharge.
 

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1989 300E
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19 Posts
I Had A/C Problems Too!

Hello,

45 - 55 psi is in the warning area for your car and you will have to determien if you want to put more 134 in your system. Consider this first though. A brand new system has a psi rating of 49psi! That is brand new, your system is how old..... you have twenty year old seals in your compresser maybe weak spots in your condenser and what about your evaporator! Oh Man if you blow the evaporator your in for hot days or a lot of work. About a month ago I converted mine over to the 134, because I had a leak somewhere and my compressor wouldn't turn on. Well, I charged it up to 50psi and blew my condenser, it was probably on its way out. I replaced it and the dryer and the lines to the condenser. I filled it again to 50psi and a few days later blew the seals in my compressor, I replaced that little $300.00 item and put in another new drier and filled it again to 50psi and the dang system would get cool but not cold! I did some investigating and foud out that the reson why is that the condensers are not big enough to make up for the loss of cooling between the 134 and the R-12. If you look at the condenser on a new 134 vehical they easily twice the size of ours! So the moral of the story is that if you want cold A/C go back to the R-12 or (Freeze12) I know many of the guys on this site claim to have gone 134 and its great and all this but I can tell you I replaced my whole system and when it was 94 outside it was about 88 in my car with the A/C on high! I don't like to sweat in my car. When I get in my Lexus I hit the A/C and at 94 outside I can grow icicles on my chin....thats how A/C should work! I can't quite do that in my '89 with new compressor & condensor but it gets cold enough I have to kick it down to low!

There are some inexpensive kits that you can use to convert back to the r-12 or you can get the kit and take them to a local A/C shop and they will probably do it for you. Here is where I got mine!

eBay Motors: R12, Refrigerant R-12 DELUXE ADVANCED A/C KIT (item 160241975656 end time May-25-08 12:16:27 PDT)

Also, overcharging the 134 will not get you cooler air, actually you would be better off taking it down a little bit!

Hope this helps you

Brian McMullin
 

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1998 300TE
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6 Posts
Discussion Starter #3 (Edited)
thanks for the info

the car was already converted to 134 when I bought it

my '02 accord and '07 pilot are both 134 and feel way colder than the '89 300TE with the 134 conversion

if the "cold" is as cold as its gonna get, then I'm going to reconsider this vehicle... probably need to move into a new model with CUP HOLDERS and an arm rest that actually provides a full arm's length of usable space...

oh, and the glove box... could it be any smaller??

and as far as the fuel door... why is it when the tank us under 1/4 full the pressure builds to the point it won't open?? I gotta open the rear door, then open the passenger-side panel, then depress the red button to release the pressure... only then will the fuel door lock open...

and another complaint... the amount of seat area is too small... the seat barely makes it to the 1/2 way point of my thighs - I'm only 6'1" and should have a much better seat area - are Germans that small?? If so, it's hard to believe as I'm of German/Austrian descent and clearly need a larger seat, preferably in a vehicle that gets better gas mileage (my accord gets way better mileage-per-gallon than the benz).
 

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1993 190e-2.3; 1992 300E-3.0, 1998 Saab 9000T
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107 Posts
The correct way to charge up the AC is to do it by amount/weight. In other words, discharge the system, rent a vacuum pump, vacuum it out for maybe 30 minutes, then put the correct amount of r134 in. It is about 85% of the amount of r12. For my 92 300e, that is 32 ounces of r134.

I have no complaints at all about the perfomance of the r134, even in south GA. However, I think the later w124's may have had some upgraded components in preparation for the r134, like a bigger condensor.
 

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99 Merc S420 (80k Mi) 07 Lexus LS460 (21k Miles)
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4,583 Posts
You need to convert back to R-12. These cars were not designed to run on R-134a. Your condensor is simply too small to make up for the lost cooling power. R-12 will take it down another 10-12 degrees F (no joke!). You can't use R-134a in the deep South and be happy in these older cars (unless you retrofit a big a$$ condensor in and some extra aux fans). I've converted some older cars back to R-12 after dealing with crappy R-134a and I've always been very happy.
 
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