1989 300SE Aux Cooling Fan - PeachParts Mercedes-Benz Forum

bolomiester · #1 09-02-2010, 09:38 AM

Can the dual aux cooling fan setup from the late model w126 cars be used as a replacement for the single fan in the earlier cars? If so would it be an easy bolt in job?

The AC on my 1989 300SE works very well either sitting still or going down the road, up to about 85F, outside temp. After that performance starts dropping off, especially when sitting still, though it stays acceptable when moving even when the outside temp hits 90F+.

The engine never overheats, even when sitting still with the outside temp at 90F+ the dash gauge peaks at just over 100C.

I just need to move more air through the condenser when the car is sitting in traffic.

Any input would be highly appearciated. Thanks!

tjts1 · #2 09-02-2010, 10:45 AM

How long has it been since the system has been recharged? I say bite the bullet and buy a can of R12 on ebay and recharge it.

macdrone · #3 09-02-2010, 05:30 PM

Engine rpm and freon charge have more to do with A/C at that point. System works best above 1K rpms. The Aux Fans come on in mine but my A/C drops in cooling at a stop also. If I put in neutral and pull rpms up to 1K bam cold as ice. Compressor just doesnt operate enough at idle RPMS. Maybe could get a bigger pulley made to bump up RPM's, check charge would be your best bet.

bolomiester · #4 09-02-2010, 06:29 PM

The charge is good, its been checked several times this summer. We've tried adding a little or taking a little out but it doesn't really change the outlet temp.

The outside temp is 82F today. Cruising the AC outlet temp is about 54F, which feels plenty cold, stopped in traffic, it went up to 65F pretty quickly.

My logic was that if MB went to the extra trouble of adding the dual aux fans on the latest W126's they were trying to accomplish something. If they succeeded maybe it would help me.

macdrone · #5 09-02-2010, 06:51 PM

Look at the fan shroud in a dual fan set up you will see the condensor is covered with plastic flappers that come up not when the aux fan hits but at speed as they are heavy and not real flexible. Crazy you would think the aux fan would lift them right up just to help the A/C, I even ordered new ones thinking mine were just hard over time. The new ones were stiffer than the old ones.

Remember to check your A/C charge with compressor engaged at almost 2k rpms low side should be about 35 psi. Cant check with compressor not engaged as the throughout pressure should peg the gage.

bolomiester · #6 09-02-2010, 07:02 PM

Quote:

Originally Posted by macdrone

Look at the fan shroud in a dual fan set up you will see the condensor is covered with plastic flappers that come up not when the aux fan hits but at speed as they are heavy and not real flexible. Crazy you would think the aux fan would lift them right up just to help the A/C, I even ordered new ones thinking mine were just hard over time. The new ones were stiffer than the old ones.

Remember to check your A/C charge with compressor engaged at almost 2k rpms low side should be about 35 psi. Cant check with compressor not engaged as the throughout pressure should peg the gage.

My indy has been helping me sort this out. I have AC gauges, and a bit of knowledge, but it's been worth it to pay him to help. He's very flexible in that sense. The compressor is engaged and we've had the low side at 35 psi. At the momoment it's at about 45 with a high side of about 250. Doesn't seem to make a whole lot of difference.

Maybe I should add that my current aux fan seems to perform normally. The low speed comes on pretty quickly when the car is stopped, and if the engine temp goes high enough it kicks into the high speed. It's just that it has to be really hot out for the engine temp to get up the level where the high speed of the aux fan kicks in. By then the AC is pretty warm.

Hit Man X · #7 09-02-2010, 07:12 PM

Quote:

Originally Posted by bolomiester

Can the dual aux cooling fan setup from the late model w126 cars be used as a replacement for the single fan in the earlier cars? If so would it be an easy bolt in job?

The AC on my 1989 300SE works very well either sitting still or going down the road, up to about 85F, outside temp. After that performance starts dropping off, especially when sitting still, though it stays acceptable when moving even when the outside temp hits 90F+.

The engine never overheats, even when sitting still with the outside temp at 90F+ the dash gauge peaks at just over 100C.

I just need to move more air through the condenser when the car is sitting in traffic.

Any input would be highly appearciated. Thanks!

No, the condenser has different bolting places.

I think '89 still had the three pole switch on the cyl head, if so get the RED switch. Kicks the fan on sooner

Get the 79°C thermo in there, this will drop temps under hood. I have run mine on it for years.

I THINK the early M103 like yours has a black fan, my '90 has a white one. From memory the white one has different blades. Check this to see if you have the black one. Replace with white.

Are the windows tinted? This helps a lot with ability to cool the car.

Is the vacuum system working? Any leaking air from defroster pod? Is the recirculation blend door working properly?

Who is checking your A/C charge?

Worst case you can just wire up a relay to the fan switch on the dryer that will turn on the aux fan when the compressor is on, and turn fan off when the compressor is off.

EDIT - the AC system in the 300SE/L is just not as good as the V8 cars due to a smaller engine driven fan and due to the fact some of the condenser does not even have air being pulled over it. Look how small the radiator is in the car.

RobertFini · #8 09-02-2010, 08:53 PM

I'm not that familiar with the fan setup on the W126, but some guys on the forum have added manual override switches to kick in the aux fans on the W124 on demand. I'm thinking about doing this for my '94 E320T because I have the same problem with the outlet temperature climbing when the car is sitting still.

Another thought just occurred to me - have you checked the operation of the viscous fan clutch and the condition of the fan shroud on the engine-driven fan? It's my understanding that those things are supposed to draw air pretty strongly, even at idle. My shroud is shredded and I don't think the clutch is engaging, but I'm not that concerned about it.

Best Regards,
Rob