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  #1  
Old 03-17-2019, 03:50 PM
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Question 1985 560 SEC - Automatic climate control works sometimes!

My AC / heater control unit (the automatic one) doesn't work. But sometimes after a long trip, it suddenly starts working again, high / low speed work fine. Then later, dead.

What the hell? Is it the AC relay or can it be some other gremlin?
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Old 03-17-2019, 04:42 PM
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The silver temperature regulator box behind the glovebox is dead. When they go, it results in erratic fan control that occasionally works, and lack of temp regulation (hot/cold only, or stuck in one mode). There are capacitors in it that leak and eat the copper traces off the circuit board.
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Old 03-17-2019, 07:10 PM
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Thanks I will check that out!
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Old 03-19-2019, 12:10 PM
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Quote:
Originally Posted by Diseasel300 View Post
The silver temperature regulator box behind the glovebox is dead. When they go, it results in erratic fan control that occasionally works, and lack of temp regulation (hot/cold only, or stuck in one mode). There are capacitors in it that leak and eat the copper traces off the circuit board.


This.



OP, you may as well have the relay box rebuilt and the PBU while it is down.
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I'm not a doctor, but I'll have a look.

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Old 03-19-2019, 01:42 PM
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And when you have the push button unit, blower, and temperature relays out rebuilding these isn't difficult.

There's a protective coating on the backside of the boards that can be removed with acetone. It's a pain in the rear, but required.

Use a voltimeter to measure the resistance on each capacitor. If it doesn't match what is posted, desolder and replace.

And while you're in there, make sure you reflow all of the solder joints one by one as they can crack.

If this sounds long, arduous, and annoying do what I did and send it to this guy: Cruise Control Repair

He is forum member JamesDean. He did a great job with my boards. I paid him $150 for the whole job.
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Going back to the original post: "Can you get the vac to blow instead?" No. Vacuums are low pressure so they by nature "suck" and nature abhors them.
1984 380SL
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  #6  
Old 04-12-2019, 03:40 PM
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Behind the dash picture


Ok so I couldnt find and silver temp regulator box, neither the vacuum block and some of the vacuum clocks needed.

If any of you have anything lying around for sale I would greatly appreciate it!

Last edited by olevik; 04-20-2019 at 11:05 AM.
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Old 05-05-2019, 07:43 AM
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Anyone? :O I'm a bit lost here, might try to get a parts car to get everything from. I cant seem to find out is my car should have a silver relay behind the glove box or not. Is this something all cars with auto climate have? Preface and facelift cars?
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Old 05-05-2019, 11:23 AM
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Post a picture of your headunit. Is your car US or ECE?

My 11/84 SD has the early system. My 87 and 90 have late, one of the poster's 86s had late too.
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Old 05-06-2019, 10:31 PM
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I was thinking that black box against the right side lower kick panel area, with the aluminum "ring" at the top was the climate control brain. Is that so, if not, what is its purpose?
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Old 05-06-2019, 10:39 PM
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Originally Posted by gear-head View Post
I was thinking that black box against the right side lower kick panel area, with the aluminum "ring" at the top was the climate control brain. Is that so, if not, what is its purpose?
Engine ECU. The temperature regulator boxes are not shown in the picture from the OP. He'd help himself a lot if he'd post a picture of which climate control unit he has.
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'86 300SDL - "The Diseasel" 189K (Totaled 1/31/19)
The Diseasel Thread - Everything You Didn't Know You Wanted To Know
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Old 05-06-2019, 10:49 PM
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Plugs are on top, he has a second generation setup. No external boxes! Also explains why has the later front flap assembly.

I only know because I found more PBUs around the house today.



Problem solved on identification!
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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
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  #12  
Old 05-07-2019, 07:15 AM
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These pushbutton units frequently have cracked solder connections on the pushbutton switches and temperature dial potentiometer resulting in intermittent operation.
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  #13  
Old 05-08-2019, 09:11 PM
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thanks!

Thanks for enlightening me about that! Good to know!

Quote:
Originally Posted by Diseasel300 View Post
Engine ECU. The temperature regulator boxes are not shown in the picture from the OP. He'd help himself a lot if he'd post a picture of which climate control unit he has.
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  #14  
Old 05-13-2019, 03:05 PM
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thanks for all the input. The car is a Japan delivered car, second gen, 1986 560. Japan cars have the same smog setup as US cars, log exhaust manifold etc. This makes me think its similar to US cars, except the big bumpers.

This is the PBU, it does not have a part number


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  #15  
Old 05-13-2019, 03:08 PM
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I tried with a different PBU but it didnt help. Dunno if that PBU worked or not! Resoldering the PBU could be an option, if I can figure out how to open it :/
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