hey people, I just wanted to know what the average ambient temperatures for a 300D. I live up in colorado and usually it gets pretty hot up here (around the nineties). And also, does the auxilary fan only work in conjunction of the AC compressor? My auxilary fan is shot and my AC system doesnt work at all (only the heater works) and i was wondering if i should shell out 200 bucks for a new fan if my AC system dont work.

thanks for replies
allan

Greetings Allan,

If your model is fairly the same as my '80 then the aux. fan doesn't come on until the a/c button is depressed and the a/c working. Your model engine should have a clutch fan for the radiator that keeps air flowing according to ambient temps. If you are getting excessive temp reading on your gauge, let's say over 98 degrees celsius then I'd image your thermostat or dirty radiator cooling fins are the culprit. We've been getting temps in the nineties as well and mine seems to be running at about 84 degrees C or close to it.

Charles

hey charles

thanks for your reply..i'm glad that i read your post because i was about to buy a new a/c aux fan even when my compressor and dryer/reciever dont work. Do you think i should replace it anyway..or should i just flush out the radiator and change the thermostat? I dont plan on getting the A/C system done till next summer. I was also told that the temperature sender device usualy goes bad and effects the calibration of the temp gauge...Have you changed this before? Also, I just went out and bought a chiltons manual and in it, they talk about a thing called a belt driven radiator flex fan where they are extremely light and will vastly improve air flow into the cooling system. do you know anything about this?

thanks for your replies
Allan

hey bill

On my 78 300D, i'm not to sure on how many blades i have on my fan. But i do know that the fan is metal and thats what came stock with the car back when my dad bought it. Is there someway that i can test to see if my fan has a clutch in it? The only info that i can give without dissmantling it is that when the engine is off and the belts aint going...i can turn the fan manualy with my hands...when i spin it...it only goes about 1/4 of a rotation.

thanks
Allan

Greetings Bill and Allan,

Sorry if I misled you allan, after reviewing the electrical diagram my car is set up differently than yours, and you do happen to have a seperate temp probe that will kick on your aux fan as Bill said. From the looks of it, I think it's the one located on top of your radiator elbow. Looks like a cheap repair if it goes bad, but the aux fan is a different story as far as price. Perhaps a good used one from a salvage yard would work fine and most likely run you less than a quarter of the price. As far as your regular cooling fan assembly goes, is it clutched or not? Just look on the front of the blade housing for a round finned item attached to it, that's the clutch if you have one. From what you said about the blades being able to turn by hand a quarter of a turn, it sounds like something is amiss with your clutch, and if you don't have one, I'd say some bolts are missing out of the mount from fan to water pump. With the engine off a clutched fan should move fully around with a small amount of resistance. The nine bladed flex fan you speak of would provide more cooling effect across the radiator and from what I see for prices, only runs around $36.00 to buy. Perhaps partshop can get this item for you as well.

Charles

hey can do and Bill

thanks for the helpful info...I just went out and bought a used aux fan from the junk yard. I installed it and it runs like my dads 300E aux fan...kinda loud but with a little clicking annoying sound. The fan seems to be a little off balance because when i put my hand on the black plate when its runing, i can feel it vibrate rough. Do you think i should keep the fan? I bought it for 69 bucks but i have a 30 day return policy.
At what temp should the aux fan turn on? My aux fan turns on at redline 250 fahrenheit (121.1 C)....I'm not too sure if this is normal. Also my radiator fan does have a clutch in it and it has 6 blades (aluminum). I'm assuming my fan clutch is bad, since it doesnt move freely when the engine is turned off (only turns about a quarter rotation). Should i replace it...its pretty expensive, costs around 100 bucks. Last, are the updated 9 bladed radiator fans in the later 81-85 300SD models? I found one off the net for cheap 30 bucks, just wanted to know if its the same fan your talking about can-do.

thanks
Allan

Greetings Allan,

I'd say the aux fan has probably seen better days. I'd return it and have them show one in operation, or hook it up to your battery before leaving the lot for smooth operation. The clutch can also be bought used as well, I have one that was used and seems to work fine. Your best bet on that one would be to get one that is still installed on a car if they have one. You should be able to see leaking fluid as well as whether the sealing ring that faces the fan in intact and seated properly. If the fan isn't kicking on at the proper temp, then the switch I spoke about in my previous post will likely need to be changed, fastlane sells them for $12 I believe.

Charles

hey guys...just wanted to say thanks to everyone for helping me out and stuff, i really appreciated it. But hopefully this will be my last batter of questions. I was looking up on the net for a new fan clutch at http://www.thebenzbin.com and all they have is a clutch called a VISCO fan clutch. Whats the difference between this clutch they sell at http://www.thebenzbin.com and the normal clutches they sell at fastlane? actually it would be best if i can get the original model # of the fan clutch (I.E 123.XXX.XX). If anyone one of you guys have this # in hand that would be great. I'm about to buy everything new off the net for my cooling system. Hope this investemt is well worth it.

Greetings,


The clutches are the same type but for the exact part number you can call Phil at the partshop info line at 1-888-333-4642 and he can give you the proper p/n for your application. Most likely it won't be a 123 number.

Charles

When I turn on my AC the fan does not come on. Todate, I've not heard the fan come on at all. I will attempt to test the fan by applying 12 volts directly to the connector. If the fan does come on at that time, what/where should I look further to determine if it is a sensor or something along those lines that I NOT activating the fan?

thanks,
jeric

Greetings Jeric,

If memory serves me right than your aux fan is controlled by the freon temp sensor located on the receiver dryer. It should be the one threaded into the top side and made out of brass. If you connect the two wires going to it and the a/c is running then the fan should start up. It comes on at 52 degrees C If your a/c has been on for a few minutes at idle the fan should be running, if not bypass this temp switch and see what happens. Chances are good that this switch is your problem child.

Charles

Hi Charles,

Thanks for the info, your advice is GREATLY appreciated. I will conduct the test as you have described. I did run the AC yesterday for a while, the whole time it was on the fan did not come on. With the temp here reaching into the high 90's I'm really concerned with the possiblity of overheating. Should the suspect sensor be the culprit does the AC have to be recharged after replacement? Again, thanks, your input is priceless as it will prevent me from chasing my tail

jeric

Greetings Jeric,

Actually this is probably one of the few items that can be removed without discharging the system. It's only a threaded temp sensor so be careful when installing it if you do happen to remove it. The brass threaded portion has a habit of breaking if you apply to much torque to it so slightly snug is tight enough. The other item located on your receiver dryer is a freon pressure switch, and can be identified because the switch looks like it takes a twelve sided socket to get it off. This one does have pressure going to it so don't mistake the two.

Charles

aiight...i'm still waiting for my parts but i was looking at the chiltons manual and they said that if i'm going to update the radiator fan to a flex fan...then i'm going to need a "spacer" between the clutch and the water pump hub. Do i really need this piece in order to use the flex fan? and if so how much will it cost and where can i get one...hopefully somewhere in my hometown

thanks for replies
Allan

Thanks Charles,

I did just as you suggested, went to the "gold" sensor, unpluged and shorted between the connectors on the wire going back to the car. No luck. So I then, applied 12 volts directly to the fan connector, NO luck. I think I should now check to ensure that power is being passed from the sensor to the fan. This done, it looks like I will be buying a new fan. Thank you so much for the trouble shooting advice, you've (and everyone else on this forum) has been a tremendous help to date.

jeric