A/C on 1987 300TD

[Garlynn]

Heya,

So, I'm new to posting at the Shop Forum, but as a lurker I've been impressed with the general level of knowledge and experience here So, let me see if you guys can help me with this situation.

I've got a 1987 300TD, "Eleanor," and she's in pretty good condition -- bought her from the family of the original owner in December 2006, and pretty much everything works (except for the rear driver's-side window, dontcha hate that? no? oh right, 'cuz you never sit back there. neither do I.) -- except for the A/C.

I took it into a shop in San Francisco last summer on a separate issue and asked them to look into it. They said the previous owner had done a half-arsed conversion from R-12 to R134a without messing with the valves, and they also said the CCU was dead. So, I asked them to fix it. They converted all the valves & seals to r134a and replaced the CCU, but advised me that they thought a new compressor, condensor and orifice tube would be required to make it fully function.

My friend is a certified HVAC tech (for buildings), and he lent me his equipment to mess around with. Yesterday, I went to work. Seems like the system, even though "fully charged" last summer with r134a, now is... empty? They gave no indication of any leaks at the shop last year. But, the pressure switch indicates that there is no pressure, and when I hooked the guages up to the high side, they didn't budge off of ZERO.

Also, the compressor won't come on, even when bridging the connection at the low pressure switch on top of the E/D.


I'm thinking I may need a new compressor, as it is likely this one hasn't been running for nearly a year. Have not yet checked to see if I can manually rotate it, though, or jump it with a wire directly from the battery.

So, here are my questions:


* What other tests, if any, should I run to confirm that the compressor is dead?
* How can I test to see if the condensor needs to be replaced?
* What is the orifice tube, and where do I order it? (I checked on www.***************, and they did not list anything like "orifice tube" or "high-pressure line filter," etc.)
* I'm leaning towards evacuating the system, attempting to pull a full vacuum, then re-charging with ES-12a. Anybody want to talk me out of it? IMHO, r134a is junk. ES-12a is probably the cheapest solution, since I believe I can get the adapters for the r134a ports cheaply to run ES-12a, and it's supposed to be more efficient AND COLDER than r134a.
* Any other thoughts?

I'm trying to go the DIY-way, and avoid taking this into All Mercedes or some other such shop. I don't like paying $100/hour for stuff I can do myself!

Any advice appreciated. Anything I learn on Eleanor, I will probably apply when I next attempt to fix Gladys, the w123 (1982 300D turbo)...

cheers,
~Garlynn

P.S. I'm doing this job in Oakland (San Francisco Bay Area), so if anybody is local... I'll buy/give you beer for a few hours of your time, if you've done this stuff before!! (I do brew my own beer, and the latest batch is quite good -- independently verified as such!)

[jcyuhn]

Sounds like you have your work cut out. As I see it, you have two main problems to solve. First, get the compressor operating. Second, determine what is leaking and repair it.

There are a lot of good old threads here on how to troubleshoot compressor engagement on the 124. I won't attempt to repeat all the information, but rather suggest you search on "Klima relay" and settle down for some reading. You'll need an inexpensive digital volt/ohm meter to chase through the electrical system and determine whether and where a problem may exist.

Once the compressor is operating I suggest recharging with 134a. It can be purchased with leak detection dye already mixed in. Drive the car until the a/c becomes weak, then go looking for the dye stained component(s). This is by far the most accurate and effective way to find a refrigerant leak.

This car does not use an orifice tube, rather it has a thermostatic expansion valve (TXV). Both perform the same function - metering refrigerant into the evaporator. An orifice tube is cheap and reliable, a TXV is more complex and gives more optimum performance. BTW, the TXV is the goldish block next to the brake booster with the high/low refrigerant lines connected to the front. Believe it or not, it's not too bad a job to replace it.

BTW, hookup the lowside guage too. There's always a chance the schraeder valve on the highside just isn't getting depressed. The lowside connection is right there up top on the large refrigerant line, just forward of the front firewall.

Best of luck,

- JimY

[dannym]

Hey welcome, thanks for coming out, from lurking that is.

Your "mechanic". and I use the term loosely said you have a orifice tube which you do not. You have an expansion valve:
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2CC0UE52J2CR0W7K5H&year=1987&make=MB&model=300-TDT-002&category=R&part=A%2FC+Expansion+Valve
I would advise against going back to that "mechanic". It make take a while but try to find a good mechanic who specialises in european cars.
Try looking on thr "Good MB Shops" forum.

I would jump power right to the comressor if you can. Jumper cables or a battery pack. You could have a bad fuse or a bad relay (next to fuses).

Danny

[Garlynn]

Thanks for the advice on the orifice tube -- or, rather, lack thereof. That makes a lot of sense. Believe me, I'm not going back to that previous "mechanic."

Also, I have done extensive searches of the archives of this site -- which is why I did not mention the KLIMA in my first post. That topic, I believe, has been covered. As far as I can tell, the PO converted from a KILMA to an ice cube (or similar bypass device) on Eleanor. Can I mention how much of a PITA it is to get my hands back into that tiny space behind the battery? Wow. I can't even imagine trying to get a multimeter in there, too -- much less, a flashlight to determine which pin-hole is which.

Finally, I don't think I asked the really important compressor question, so please allow me to re-state it:

If it turns out that this compressor is toast (which I will do further tests to confirm or deny)... should I replace it with a new NIPPONDENSO, identical model -- or switch to a different compressor? If so, which one? I've heard that Mercedes will do an equipment exchange on the compressor, and take back the old one for re-manufacture. Is this approach recommended?

Thanks for the replies.

cheers,
~Garlynn

Just fix the system correctly and recharge with R-12, don't waste your time on that other stuff. I tried R-134a for a while and converted back to R-12, there's no good reason to use anything else.

[compress ignite]

The system is set up with the 10PA15C or 10PA17C compressor's operating
characteristics/specifications.
You'd have to know a lot more than I do to re-engineer/retro-fit another type
compressor.

You can take a stab at rebuilding your old compressor yourself,if you feel
handy enough.

http://www.pelicanparts.com/techarticles/911_Nippondenso_rebuild/911_Nippondenso_rebuild.htm

OR call: http://www.ackits.com/

[Garlynn]

Originally Posted by compress ignite

The system is set up with the 10PA15C or 10PA17C compressor's operating
characteristics/specifications.
You'd have to know a lot more than I do to re-engineer/retro-fit another type
compressor.

OK, fair enough. So, if the compressor is gone, I should look to just find a newer version of the same type.

Doesn't Mercedes have an exchange program for the A/C compressor...?

[compress ignite]

Call ACKITS and compare their price with ANY dealer's

(This is why we call them Stealers)

Re-Read reply #6 above

[jcyuhn]

The MB dealer will happily sell you a new or rebuilt compressor, same as any other part. I've never heard of any kind of a special exchange deal. As others have stated you can get a much better price on a compressor elsewhere.

Have you measured the compressor clutch coil resistance with an ohmmeter? I wonder if the coil is open.

Have tried turning the compressor by hand to verify that it is free?

- JimY

[Garlynn]

OK, I dropped them an email (time difference means they were already closed for the weekend by the time I got around to it today) asking for a quote on a compressor for a 1987 300TD. Will do the required tests over the weekend to confirm that the compressor is, indeed, gone.

Also, what about barrier hoses -- I've heard that Eleanor may have not had these originally, and I suspect they may not have been installed when she was converted to r134a. I've heard that they may be required to keep r134a in the car. Any way to check for their presence, or lack thereof?


" Have you measured the compressor clutch coil resistance with an ohmmeter? I wonder if the coil is open."

Good advice. My multimeter died last weekend. As soon as I track down a new one, will perform it.

Finally... anybody know of any way to check the condensor to see if it is functional or needs replacement? Pressure test? Anything?

thanks!

cheers,
~Garlynn

[babymog]

Barrier hoses were not necessary with R12. Most people here feel that the small difference in cost justifies recharging with R12 to save fuel and have colder A/C in southern climates, this also saves replacing hoses and condensors to accomodate R134a.

My '87 has original hoses and R134a, has not had a leakage problem. Cold A/C, converted by the PO or I would have stayed R12, if it ever needs significant service it will go back to R12.

[dieseldiehard]

Originally Posted by Garlynn

OK, fair enough. So, if the compressor is gone, I should look to just find a newer version of the same type.

Doesn't Mercedes have an exchange program for the A/C compressor...?

There are lots of places for compressors besides the dealer (email me for a list) and I would even consider an wrecking yard compressor if I took it off myself, realizing there are some risks associated with that but not a huge risk as something like say a used engine or transmission.
Some AC mechanics will use a UV dye to spot leaks after a customer complains of a dry system, makes it visible after the gas is gone, others believe that stuff doesn't belong in the system I won't take sides in that argument but I know there is dye in my silver '87 300D because thats how we found a leaking seal (at the compressor). I have a friend on the peninsula that does AC work for me, I try not to DIY AC work, BTDT.
If at all possible, replace the compressor seal and both Shrader valves as a minimum, I have seen a leaking Shrader valve on a 123 that cost me a bundle.

I have an upcoming AC shotgun retrofit coming up on an '87 300D, I have accumulated a new condensor, new compressor (may have been old stock) Nippondenso 10PA15C OE, new dryer. All I need is the evap. and expansion valve. I'll probably change the heater core also when I have the dash out (its going to be a big job! and thats a good time to look at the heater core also, its another notorious leaker in early 124's)
I suggest going with R12 only. And if you need one, there is a good shop in San Rafael (A&C) I don't know any in the Oakland area.
Reid

[babymog]

Not to hijack, well maybe.

I've read as many of these threads as I've been able to find, and it seems that the '90s 124 has evaporator failures, but the '87s don't. '87 failures seem to be more of compressor failures. Anyone had an '87 124 evaporator failure?

[jcyuhn]

Originally Posted by babymog

Not to hijack, well maybe.

I've read as many of these threads as I've been able to find, and it seems that the '90s 124 has evaporator failures, but the '87s don't. '87 failures seem to be more of compressor failures. Anyone had an '87 124 evaporator failure?

I have.

[doxland]

I have