350SD Climate Control 100% non-functional - vacuum problem? - PeachParts Mercedes-Benz Forum

Blevinsax · #1 09-30-2006, 12:07 AM

I just picked up my 350SD from the mechanic from a tweak to my GreaseCar system (which is perhaps now working properly - I'll ultimately see how it does tomorrow) but on the drive home, I realized that I have NO climate control at all. Nothing. I'll elaborate...

None of the buttons activate anything, including that A/C buttons - they do not turn on the fan nor the compressor. The recirculation button does nothing and does not light up when pushed. I have no fan at any level at all - granted it was acting up last week prior to the mechanic's visit, but the fan would kick in if I thumped the dash under the glove box. The defroster does not work, either. Although it was quite hot here this evening, I believe that the air that was wafting through the vents while I drove was heat, even with the temperature dial turned all the way to the coldest position. Seems as though my climate control has completely shut down and I am left with nothing but oozing heat.

Here's my amateur theory - I recently had my EGR removed (for testing, thanks to Brian C.'s testing kit) and the mechanic disposed of the vacuum hose that went to it, but I'm not so sure that they plugged it at its origin. If this is the case, wouldn't this cause a considerable leak in my vacuum system? I say this because I have also noticed that my shut-down time has been longer than it was before - the engine does not run on very long, but it does seem to spin down slower than it did prior to the EGR removal when it was an almost instant shutdown. Might it be possible that this hypothetically open vacuum connection could be causing these random (perhaps not-so-random) problems? If so, would someone be so kind as to help me find it so I can plug it if it is still open?

Any and all input would be greatly appreciated and is welcome. I have searched other threads, and will continue to do so, but if anyone knows of another thread from which I could benefit from reading, please point me in the right direction.

I'm tackling this car one problem at a time and with the confidence that eventually I will get *almost* everything done!

SD Blue · #2 09-30-2006, 12:39 AM

I could see where an incorrectly modified vacuum system might give nothing but default defrost air but not a completely inoperative system. I would lean more towards a fuse problem or something left disconnected for the situation you are describing.

Jeremy5848 · #3 09-30-2006, 02:28 AM

I agree with Sam -- a completely inoperative ACC is almost certainly an electrical problem, a fuse or connection somewhere. Check all your fuses, see if there's a separate in-line fuse for your ACC. Look under the dash and in the engine compartment for loose wires. Take the car back to the mechanic and apply blame -- maybe he'll have the courtesy to look guilty.

Hit Man X · #4 09-30-2006, 02:29 AM

My blower fan fuse was bad on my SDL when I picked it up.

Blevinsax · #5 09-30-2006, 02:32 AM

Quote:

Originally Posted by Hit Man X

My blower fan fuse was bad on my SDL when I picked it up.

Did that affect the whole system or just the fan?

My fan has been screwy for the last couple weeks, but with the 'thump' under the passenger side dash I mentioned before, it would kick in and worked fine until I shut the car down again.

Hit Man X · #6 09-30-2006, 03:18 AM

Made it seem like nothing worked... no blower fan, no heat, no vent, etc.

Blevinsax · #7 09-30-2006, 03:22 AM

Quote:

Originally Posted by Hit Man X

Made it seem like nothing worked... no blower fan, no heat, no vent, etc.

Here's the big question - did the A/C buttons still activate the compressor? Right now mine do not. Literally nothing works at all.

Hit Man X · #8 09-30-2006, 03:53 AM

Has not worked since I owned the vehicle.

Compressor clutch locks, then blips off. I'm down to the speed sensor or the clutch, both are cheap. Maybe $45 for the SS and about a buck-ten for the clutch. PBU works, Klima is new, pressure sensor works.

Shorebilly · #9 09-30-2006, 05:24 AM

G'mornin folks,

Maybe there should be a Vacuum section on here.....

My '85 300D-T has been having some similar problems.....after tracing most of the under hood components....and testing with a "MiteyVac"......I have determined that I am getting way too much air into my system......this appears to be coming from the "Vent to Passenger Compartment" line (as designated on most schematics.....

Yes it does affect the Klima Control......mine was working without the need to "thump" the dash......before I changed the "Vent Filter".....

I am still looking into my system.....will post more as I learn....see other posts by me from yesterday....

What does the Vacuum Converter do?????

SB

Blevinsax · #10 09-30-2006, 09:10 PM

Well, I decided to dig into this one myself, so I opened the hood and started checking things. The first place I went was the fuse box - sure enough fuse #5 was OUT, as in REMOVED, NO FUSE - Jackass mechanic left it out, probably because he recognized a problem but didn't want to invest the time to find it, so he just gave it back to me with the fuse out. I put it back in and everything started working perfectly. I took the car out this afternoon for a drive around town and everything seemed to be fine, then I noticed the temperature gauge was running a bit higher (about 100 - 105C) than it had been since I had the cooling system repaired. That was waiting in line for the car wash - after the car wash it cooled back down, but when I got it back home and into the garage, all the climate control failed again. I popped the hood, checked fuse #5 and it is there, looks to be intact (I don't have extras around, so I couldn't put another in to test) but I get nothing from the climate control.

I also noticed fuse #5 controls quite a few things on the car, including the water pump and aux fan relay - that may explain the temperature rise I saw this afternoon. So, to avoid potential overheating I should not drive it until I get this squared away.

Any other suggestions?

Hit Man X · #11 10-01-2006, 12:57 AM

Okay, with the fuse in... what does it do? Start from there.

Blevinsax · #12 10-01-2006, 01:31 AM

Quote:

Originally Posted by Hit Man X

Okay, with the fuse in... what does it do? Start from there.

With the fuse in I have no fan, no A/C compressor, no defroster, and no air recirculation in the climate control - it is totally non-functional. I am also concerned that the other items on that fuse may be out - like the water pump, aux fans, etc. Since the car did heat up today after having significant work done on the cooling system recently, that seems to be a sign that something is awry.

I need to confirm that the fuse is bad - I have no extra fuses, so I will try to pick some up tomorrow. I do not own a meter to test, either - sorry, I'm not much of a mechanic.

Worst case scenario - if the fuse is NOT bad (it looks fine; I know looks can be deceiving with fuses, but it looks solid across) what might be the problem? Obviously something is stopping the flow of power over this circuit, I just have to figure out what it is. As I learned from my previous experience with the glow plug relay, a process of elimination seems to be in order.

Where to begin....

Hit Man X · #13 10-01-2006, 01:48 AM

I'd start with a new fuse box of fuses. I had some that appeared fine... stuff didnt' work.

I used a Dremmel to polish the tabs too. THEN you can verify why nothing blips on.

Could be that PBU is infact dead...

Blevinsax · #14 10-01-2006, 01:50 AM

Quote:

Originally Posted by Hit Man X

I'd start with a new fuse box of fuses. I had some that appeared fine... stuff didnt' work.

I used a Dremmel to polish the tabs too. THEN you can verify why nothing blips on.

Could be that PBU is infact dead...

Sorry, showing my ignorance here - what is the PBU? (Tell me now and I'll always know from now on! Thanks!

)

Hit Man X · #15 10-01-2006, 02:08 AM

Push Button Unit.

Could be a bad Klima relay. That's under the hood, driverside right near fire wall. Sits beside the OVP (overvolt protection relay) which is red