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AC Fan Randomly Stops - Question

3K views 16 replies 5 participants last post by  bereng 
#1 ·
Have a weird thing going on with the AC system in my ’88 560SL. Using the AC system, it works (fan blows and cold air), then just stops. No more air flow, then it will just turn back on and work fine the stop again. This seems to happen randomly. I have the dial set to all the way cold as it's super hot here in Texas Restoration still in work so I haven’t driven the car too much yet but need to address this soon.

Any ideas or pointers?
 
#5 ·
well, I took the AC controller unit apart as much as I could (being able to see the solder spots). Most of the insides looked really good. Using a magnifying glass, I found several suspect solder cracks and re-soldered those. Put all back together and no change, dang it.

When I turn on the AC, it will work fine for a bit and then the whole system just stops. Blower motor stops, AC clutch disengages. Then system comes back on, runs a bit, then stops.

Not know this system good, do you all think its the HVAC controller which is the issue? I assume it is as if the High Pressure switch was engaging to turn off the compress, that has noting to do with the blower, as it should never turn off until the button is pushed to turn it off, right?

If the consensus is I need a rebuilt controller, any suggestions for a place to purchase one?

thanks
 
#7 ·
Thanks Roncollo. On your #120, I just took out the (N29/1 Electronic Blower Control Unit) and looked it over. The number 6 pin was a little discolored. So I removed the outerbox and re-solder that connection as it was suspect. Put it back in, turned the key on and the blower will run and run, no issue. That pin gets warm but I think its the high fan setting. But as soon as I start the car, I have the same symptom. The AC system/Blower run fine for a bit (30 seconds) and then turns off (clutch and blower) then comes back on.

Now I will mess with the Temperature Regulator (the silver box what you named as the N22/1 Control unit)
 
#12 ·
What are suggesting to do? Are the push buttons replaceable. Or are there also spots to re-solder on them?

I tried to remove the cover surrounding the push buttons but appears I have to remove all the buttons so that can be removed. Is this true? I pulled hard on those buttons but they weren't coming off. The push buttons parts were under the large squarish circuit board. I wasn't sure on how to get that out of the way as I didn't want to break something. I see on your thread that you took yours completely apart; I just wasn't sure about taking it down further.

But appears I need to so I can get at the push buttons. Any pointers appreciated.

thanks
 
#13 ·
iirc if you didn't remove the push buttons you didn't gain access to the full double sided board to resolder *all* solder points (not only those you saw cracked with a magnifying glass). This was my go at it: Reparacion centralita AC - Foro Club w107 España I would recommend taking it fully apart + temp wheel + fan speed 3 push button unit, repeat: completely apart and resoldering *all* points. My 2cts.
 
#14 ·
I think I found the issue with the AC & blower turning off whenever it wants. The electronic connection at the end of the key switch seems to be the culprit. Jiggling the key when the blower/AC compressor have stopped, seems to make them restart. Plan to replace the end of the key switch and hope this solved the issue.

But, now that the AC system is running, I am getting water on the floor board. All four drain pipes are clear. It's the joint between the lowest AC evaporator box piece and the one it connects too.

Of course the car just keeps presenting problems, never stops.....
 
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