A/C and Aux. fan question? - Page 2 - PeachParts Mercedes-Benz Forum

abe g · #16 06-14-2005, 05:23 PM

Dear Boys: I posted 3 times for help and not one answer to my questions on 450sl 1977 aux fan . Repeated searches led me to your suggestions: How can I retrieve the info on by passing wiring and hook up direct on and off for aux fan? What checks to do on switch (location on thermostat housing?) or how to bypass switch for check? Any help after 4 days of no answers would be much appreciated. Regards, Abe G

leathermang · #17 06-14-2005, 05:42 PM

"I posted 3 times for help and not one answer to my questions"

I will bet that was not in the Diesel Forum....

RockinWagin · #18 06-14-2005, 09:42 PM

Quote:

Originally Posted by abe g

Dear Boys: I posted 3 times for help and not one answer to my questions on 450sl 1977 aux fan . Repeated searches led me to your suggestions: How can I retrieve the info on by passing wiring and hook up direct on and off for aux fan? What checks to do on switch (location on thermostat housing?) or how to bypass switch for check? Any help after 4 days of no answers would be much appreciated. Regards, Abe G

I don't have a manual for your car, do you? The manual on my car provides the following:

abe g · #19 06-15-2005, 08:57 AM

Quote:

Originally Posted by RockinWagin

I don't have a manual for your car, do you? The manual on my car provides the following:

Thanks for your help, no manual showing these details. unable to read (too small) even enlarged. Can you fax me copy? 516-621-1468. Thanks again, Abe G

tenknots · #20 06-15-2005, 09:51 AM

Abe,
Does the fan come on when the pressure/temp switch on the reciever/dryer is jumped? If so, you know the fan, and relay are OK. To check the switch on the thermostat housing, remove the wire (I assume a single wire system) and ground it while the car is running - the fan should come on. If not, the problem is liely the t-stat switch.

Without a wiring diagram,I can't say how to add a manual switch to the fan. Assuming the relay is OK, you just need to find which pins are used to run the fan and run a switch to close them.

abe g · #21 06-15-2005, 11:25 AM

Dear Ten knots: Thanks for your help Does this 450sl 1977 have a relay to operate the aux fan? Is this ocated above the fuses? Where and how to identift relay? Again Thank you, Abe G

1simpson@bellsouth.net · #22 09-03-2021, 03:47 PM

Quote:

Originally Posted by SD Blue

Yes, what I am saying is the aux. fan only comes with 105* engine coolant temp. and never seems to operate as a function of the air conditioning. Sight glass is clear, radiator and condensor coils have been cleaned and the clutch cycles on the compressor. But the only time I get cold air is when the aux. fan cycles on if/when the engine ever reaches 105* engine temp.

I know I need to connect some guages to actually determine the refrigerant operation of the air conditioning but I get the feeling that I may have either an electrical problem or a failed pressure switch on the receiver dryer. From what I see on the schematic, I think I can jumper the press. switch plug and check the relay, fuse and wiring portions of the system. Since I would have to purchase or borrow some R12 guages, I would like to ensure the rest of the system seems to be in operating condition.

My question is, shouldn't the press. switch usually be activated and the aux fan on nearly all of the time when the air conditioning is on?

I’m pretty sure we are talking about 100 deg Celsius. The mixture has a higher boiling point than 100 C but that’s enough to call for the aux fan.

engatwork · #23 09-03-2021, 03:59 PM

Contact Rollguy on here. He has a kit that will turn the fan on anytime the compressor is powered up.

jbach36 · #24 09-12-2021, 01:29 AM

I had my car converted over probably 8 years ago for $200 or so. Seems to me they used to charge $2,000 to do that. Find a GOOD mobile mechanic.

That said I think R12 is colder than the new stuff but I do ok with what I have.

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