Learning about the 603 3.5 - Page 2 - PeachParts Mercedes-Benz Forum

dieselbenz1 · #16 10-11-2018, 07:06 PM

The w140 and w210 series have full diagnostic and some control of the AC system through the control panel. That is not available on the w126.

Doesn't turning the AC on kick on the aux fans? I have no need for AC so I really don't know.

JHZR2 · #17 10-11-2018, 07:08 PM

Not on mine at least!

renaissanceman · #18 10-11-2018, 10:41 PM

My W124 hardly ever kicks on the aux fan (which is super frustrating, actually) which makes the A/C get pretty warm at stoplights. I've done everything short of wiring it to energize with the compressor, including swapping that switch out with one that would energize the fan at a much lower pressure.

I've found that on the highway, the A/C runs super cold (like 30's cold) but at a stop it sucks due to the lack of air flowing across the condenser and the 600rpm idle...

Diseasel300 · #19 10-11-2018, 11:19 PM

According to the FSM, the Aux fan is cycled by the switch on the filter/drier. If you short the 2 wires together, the fan should come on low speed. If it does, then the switch is bad or the refrigerant charge is low. If it doesn't, you have a bad relay, bad resistor, bad fan motor, or a wiring fault.

If the refrigerant charge is correct in the A/C system, the Aux fan should run on low speed constantly with ambient temperatures in the 80s or above.

The Aux fan is really there to help the A/C condenser. If your engine is running hot, especially at low speeds, it's time for a fan clutch.

renaissanceman · #20 10-11-2018, 11:25 PM

Quote:

Originally Posted by Diseasel300

According to the FSM, the Aux fan is cycled by the switch on the filter/drier. If you short the 2 wires together, the fan should come on low speed. If it does, then the switch is bad or the refrigerant charge is low. If it doesn't, you have a bad relay, bad resistor, bad fan motor, or a wiring fault.

If the refrigerant charge is correct in the A/C system, the Aux fan should run on low speed constantly with ambient temperatures in the 80s or above.

The Aux fan is really there to help the A/C condenser. If your engine is running hot, especially at low speeds, it's time for a fan clutch.

In my case, shorting the switch causes the fan to come on. Without R12 in the system, I believe the pressures never get high enough to trigger it, even with the lower pressure switch...

Diseasel300 · #21 10-11-2018, 11:33 PM

Quote:

Originally Posted by renaissanceman

Without R12 in the system, I believe the pressures never get high enough to trigger it, even with the lower pressure switch...

If running R134a, the head pressure will be higher than with R12 if the system is charged correctly. Just going by the 80% by weight rule of thumb will have you still undercharged, at least on the W126. My experience in my own car is that it'll cool like crazy when the car is moving, but quickly warms up at idle when undercharged.

JHZR2 · #22 10-12-2018, 12:43 AM

Quote:

Originally Posted by renaissanceman

My W124 hardly ever kicks on the aux fan (which is super frustrating, actually) which makes the A/C get pretty warm at stoplights. I've done everything short of wiring it to energize with the compressor, including swapping that switch out with one that would energize the fan at a much lower pressure.

I've found that on the highway, the A/C runs super cold (like 30's cold) but at a stop it sucks due to the lack of air flowing across the condenser and the 600rpm idle...

My experience is temps creeping up at non-interstate speeds (especially in traffic though), but the difference is that on mine, the engine temp creeps up to nearly 100, but the AC is still working great.

Quote:

Originally Posted by Diseasel300

If the refrigerant charge is correct in the A/C system, the Aux fan should run on low speed constantly with ambient temperatures in the 80s or above.

The Aux fan is really there to help the A/C condenser. If your engine is running hot, especially at low speeds, it's time for a fan clutch.

I haven't put gauges on, and do see abubble or two in the sight glass, but the AC works surprisingly good. Impressively so IME.

I thought about the fan clutch, but any test I attempt can't cause the fan to spin more than a blade or two further and then stop. It's certainly not spinning free, there's lots of friction which indicate to. Emthat it's generally ok.

Diseasel300 · #23 10-12-2018, 09:32 AM

Quote:

Originally Posted by JHZR2

My experience is temps creeping up at non-interstate speeds (especially in traffic though), but the difference is that on mine, the engine temp creeps up to nearly 100, but the AC is still working great.

I haven't put gauges on, and do see a bubble or two in the sight glass, but the AC works surprisingly good. Impressively so IME.

I thought about the fan clutch, but any test I attempt can't cause the fan to spin more than a blade or two further and then stop. It's certainly not spinning free, there's lots of friction which indicate to. Emthat it's generally ok.

Mine behaved the same way. Fan clutch "passed" the usual tests but it'd get hot in traffic, especially in the summer time when the cabin was hot and the A/C was really cranking. When I replaced mine, I took the opportunity to upgrade to the 11 blade fan from the turbo 606. It really made a profound difference in how cool the engine stays (even in 109˚ temps this summer it never went above 90˚) and how well the A/C performs.

Another datapoint on fan clutch issues is my SL. No idea how old the clutch was that was on it, it wasn't OEM, but it hasn't been touched since '98 when we got the car. It felt like it had decent friction, it would shred a newspaper shoved into it, but the car would routinely overheat, especially at 45-50mph speeds. I did EVERYTHING to the cooling system, convinced that the fan clutch wasn't the issue. I finally decided to replace it, basically out of other ideas, and guess what......no more overheating. All the rest of the work I did to the engine was pointless, it was that stupid clutch causing all my grief even though it "tested good".

Just my own experience and 2¢

JHZR2 · #24 10-12-2018, 12:58 PM

Quote:

Originally Posted by Diseasel300

Mine behaved the same way. Fan clutch "passed" the usual tests but it'd get hot in traffic, especially in the summer time when the cabin was hot and the A/C was really cranking. When I replaced mine, I took the opportunity to upgrade to the 11 blade fan from the turbo 606. It really made a profound difference in how cool the engine stays (even in 109˚ temps this summer it never went above 90˚) and how well the A/C performs.

Another datapoint on fan clutch issues is my SL. No idea how old the clutch was that was on it, it wasn't OEM, but it hasn't been touched since '98 when we got the car. It felt like it had decent friction, it would shred a newspaper shoved into it, but the car would routinely overheat, especially at 45-50mph speeds. I did EVERYTHING to the cooling system, convinced that the fan clutch wasn't the issue. I finally decided to replace it, basically out of other ideas, and guess what......no more overheating. All the rest of the work I did to the engine was pointless, it was that stupid clutch causing all my grief even though it "tested good".

Just my own experience and 2¢

Very interesting. I have only seen nine blade fans, but I am only familiar with non-turbo 606 engine.

Does this fit into the original W126 radiator shroud, or does the part from a w210 have to be installed?

Can the same clutch be used between the 603 fan and the 606 fan? I believe one clutch is bimetallic while the other is viscous, but I’m not sure if that really matters much. I guess the real question is if it is a drop in replacement.

renaissanceman · #25 10-12-2018, 01:35 PM

It's a drop in replacement on my 124, but quite hard to do with the limited space.

dieselbenz1 · #26 10-12-2018, 01:55 PM

I've taken out a fair number radiators from pick n pull and I'm always amazed at the amount of debrie that collects between the condenser and radiator.

JHZR2 · #27 10-13-2018, 09:59 PM

I had just enough time today tojumper the red pressure sensor on the AC system. Aux fans came on, fairly silently I might add. I was expecting to hear them roar on like on my w123. I had to double look to verify.

Strangely, there is no resistor down by the abs pump, so I'm not entirely sure where to check on that. Perhaps more combing through the electrical manual...