95 E300D A/C stopped, came back, now gone - PeachParts Mercedes-Benz Forum

Kaiser Soze · #1 09-02-2007, 07:26 PM

Someone else had the exact same problem as me, but I have not been able to find the thread. Earlier this summer I got in to my car ( 95 E300D ) and the A/C didn't turn on until after about 2 minutes of driving. It got to the point where I would be lucky if it turned on at all. It would either blow nice cold air, or nothing at all. By now It has completely stopped. I have since turned off climate control, checking every once in a while if it might work again to no avail. When I turn cc on I can hear the noise you would normally hear on such a car (I think it's the compressor) but nothing actually blows out of the vents. When it's on I can also hear a faint noise like air is blowing slightly from somewhere within the vents or something. If I remember correctly, in the other thread someone suggested to check the poly v belt. It looks nice and tight. Although now I doubt it's the belt, would there be anything else that could cause it to slip? I checked, twisted, and replaced fuse #7 which did nothing. I tried to run cc diagnostics but the only instructions I found we're for the c class and I don't have a rest button on my car anyway. I'd also like to apologize for not following up on one of my previous posts. By the time I had solved the problem, the thread was buried and I couldn't find it on a search engine.

Kaiser Soze · #2 09-04-2007, 12:54 PM

I didn't think this would be such a silencing problem, at least for you guys. By the way, the heater doesn't work either.

TMAllison · #3 09-04-2007, 01:13 PM

If understood correctly, your AC works but the fan is not blowing air out of the vents....search for fan blower motor and regulator, then duovalve.

You can easily find threads you posted to, or started, by clicking on USER CP (upper left side of menu bar on every page).

Kaiser Soze · #4 09-04-2007, 05:45 PM

Thanks Terry. I just figured out that my options were set to not automatically subscribe to threads started or posted to. Is there a simple way to verify that it is in fact the blower motor? For that matter, any of the other parts you suggested? If not, my plan is to buy one from the dealer and return it after checking to see if it works. I just bought the cds from ebay so hopefully I will be able to figure these things out for myself.

jeff (moose) · #5 09-04-2007, 05:57 PM

I am having the same exact problem and assume it is the control but would like some diagnostic help.

Thanks in advance

saumil · #6 09-04-2007, 06:26 PM

Beware, you cannot return electrical parts once you leave the dealer's parts store.

Kaiser Soze · #7 09-04-2007, 10:58 PM

So I guess I'll check the blower motor first, unless they consider that electrical. Unfortunately Auto Zone doesn't have it.

saumil · #8 09-04-2007, 11:21 PM

The blower not working could be due to many reasons not just a bad motor. Check the blower motor fuse (on my 87, 260E, it is outside the fuse box, near the ignition control module), this fuse sometimes has a fine hairline crack that results in intermittent functioning. It could also be the ignition switch, either wiring or its contacts. It could also be the climate control unit not sending the control signal to the blower motor regulator. I am not so familiar with your car but on my 87, 260E, there is a 3 terminal connector on the firewall behind the brake booster. The first terminal towards the engine is the ground terminal, the middle has the battery voltage and the third terminal towards the fender has the control coltage from the CCU. If you dont get battery voltage on the middle pin when the car is on, the problem is with the ignition switch, on high fan setting, if you dont get about 8V on the control terminal, the CCU is not sending the control voltage. If these voltages are fine, then it could either be the regulator or the motor itself. Let us know what you find.

jeff (moose) · #9 09-07-2007, 09:56 AM

This would be a metal strip type fuse mounted inboard of the fusebox?

Stinkindiesel · #10 09-07-2007, 04:33 PM

I think Jeff might have it. Believe it or not, I've seen temerature sensitive strip fuses before. Would work fine for a while, then not. Be sure you actually pull the strip fuse and take a close look at it. Just because it looks OK while it's screwed down doesn't mean it's good. I've seen these things look fine in situ, and then disentegrate when you removed them.

Gary (BTDT)
1995 E320

Kaiser Soze · #11 09-07-2007, 06:00 PM

Covered by a little plastic enclosure, just inches forward from the fuse box, lied a corroded and cracked 30 amp fuse. I replaced it, and sure enough the ac is back up and running. I am so glad that every problem I've had with this car so far has been fuse related. I should sell it and buy a 99 before my good fortune will runs out. Thanks for all your help.

jeff (moose) · #12 09-07-2007, 06:24 PM

I found 2 red fuses in one box and 2 boxes containing 2 metal strip fuses. I am, going to replace the red fuses and remove and inspect the strip fuses. i still have blower but only within a few minutes of start up and not always then.,

Where is the box with the 3 wires? T have not seen anything with 2 wires other than the 2 fuses I told you about earlier.

I hope i can be so lucky as to have a fuse solve my problem.

I had a check engine light that ended up being a bad conmnection at the air temp sensor. I will all fixes were as easy.

Thanks in advance.

Ian Hillerud · #13 09-14-2007, 01:34 AM

Thanks Saumil S. Patel…

My situation with a '93 300E:

Blower motor quit - found and replaced bad 8A (white) fuse in adjacent fusebox (all main fusebox fuses checked out OK with conductivity tester)

Occasionally the motor comes back to life and works at various speeds. (Bumps and door slams have no effect.) Push button control unit seems fine.

I pulled the motor out today and replaced the brushes. Bench tested at length and working fine, but it failed to work when reinstalled.

Suspected the Porcupine regulator except that the fan sometimes works - and at various speeds. Figure that it is probably something else…

Removed blower harness and checked voltage at the connector behind the master cylinder with ignition, climate control on: no voltage across the posts for the red and black harness wires. However, there was a 1 Volt reading (low fan setting) and a 9+ Volt reading (High Fan) between the yellow and black posts.

Perhaps this is correct but I would have expected the center post (for the red blower harness wire) to be live with +12 V and the yellow wire to signal the porcupine to drop that voltage to the desired setting? Unfortunately, I 'm not entirely sure how these things work.

If the Red wire post is supposed to be hot, is there a mystery fuse or hidden relay that could be causing this failure?

-> From post #8 above, the indication is that the ignition switch is faulty - are there any other reasons for no voltage at the middle terminal post for the heater motor wiring harness??? Any easy way to confirm that the ignition switch is to blame???

Thanks, Ian

jeff (moose) · #14 09-14-2007, 09:29 AM

I thought I posted the good news that I found a bad strip fuse(one I ohmed and found to be good) and just as noted it felt like it wold turn to dust if I rubbed it with my fingers. Thanks for the help

saumil · #15 09-14-2007, 10:28 AM

Ian: Yes there is another fuse outside the fusebox, atleast in my 87, 260E and it is a 30A fuse, which in my car is right in front of the fusebox in a small rectangular plastic box. This is the fuse that has hairline cracks that give rise to intermittency. Temporarily, you can connect a wire and check if the problem goes away. If not, then, given that you have missing voltage on the power pin on the 3 pin connector, your problem is with the ignition switch. Either some terminals have come loose or the switch internally has bad contacts.