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Old 12-26-2007, 04:52 PM
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merry freezing christmas......ACC issues....not for the "purist'

well, as we left the inlaws house on Tuesday morning, smoke started rolling out of the center console- the CCU board was toast. I am not sure the failure mode, or why, but I ended up pulling the unit and driving home with no heat.


not a big deal for the family- the three of them snuggled up in the backseat with blankets and the new portable DVD machine playing Simpsons movie.

I was pretty chilly by the end of the 3 hour drive.

I did have a fuse on the water pump, have not even checked if the pump seized or what.

my BIG ? is does anyone have a wiring diagram of the CCU circuits? I am thinking that I will put a 3 way toggle for the fan- High, Low and off speeds. then, fix the defrost vent and foot vents open. maybe toggle for the monovalve, or use the fan to control heat.

I am pretty confident of my ability to figure this one out, but a diagram would help immensly. I care not for the variuos vac pods, etc, I would simply like some heat. I am facing this issue on my daily driver TD, and the D I just got also has a fried board- I am thinking why spend $400+ on 2 poorly designed , fault prone systems, when with a few toggles and relays I will have reliable heat? I have a small pile of relays, prolly would cost almost nothing out of pocket.

well, hope you all had a more enjoyable holiday.......

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Old 12-26-2007, 04:56 PM
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Unplug your mono valve in the interim for heat. The default is "open" position
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Old 12-26-2007, 05:06 PM
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yup- I know that, but up here, it is too cold to not have a functioning fan. I am thinking I will go out and look over that crazy fan relay reostat thingy on the front wheel well. shoul be able to jump it there to get some air moving.
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Old 12-26-2007, 06:02 PM
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Quote:
Originally Posted by mobetta View Post
yup- I know that, but up here, it is too cold to not have a functioning fan. I am thinking I will go out and look over that crazy fan relay reostat thingy on the front wheel well. shoul be able to jump it there to get some air moving.
You could simply wire 12V directly to the fan via a switch in the cabin. However, full blower speed with full coolant will cook you pretty quick. Modulation of the system is the problem.........and the stock components do it quite well when they are in proper operating condition.
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Old 12-26-2007, 06:08 PM
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This may help, then again, it may not. '82 and '83 at least.
Attached Thumbnails
merry freezing christmas......ACC issues....not for the "purist'-file-117.jpg  
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Old 12-26-2007, 06:10 PM
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I did get the CCU board apart- and dont see any burnt items inside- but it sure does smeel funny. the board from the new 85 D is toasted. burnt right thru the case.

I know I wont want full fan and full coolant flow- that is why I hope to get high and low fan speeds- hopefully I wont have to cut into the stock wiring- maybe just use-(Gulp,!) splices- to get the fan blower straightened out.

My TD had a webasto in it at one point, so there is actually a relay and wiring from the old webasto control box over to the fanspringrheostatthingybox. maybe I can just jump a switch over to that relay.
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Old 12-26-2007, 06:14 PM
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Originally Posted by toomany MBZ View Post
This may help, then again, it may not. '82 and '83 at least.
yeah-Thanks, I have that from the FSM. thing is, in real life, there are many more wires going to the CCU/ACC box. I was hoping for some more detail. I suppose If I was out in the garage, testing leads, etc, I would prolly be done by now
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Old 12-26-2007, 06:17 PM
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sorry to hear about your cold commute. i picked up a sweet used CCU on ebay from a guy in calif. for 100 bucks shipped. i know its kind of a gamble buying these used but he carried a 30 day guarantee on it. i installed it about 3 weeks ago and it works perfect. i think the guys store was called europarts. good luck and happy holidays.... jim
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Old 12-26-2007, 08:30 PM
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well- dismanteled the board. it has some discoloration, but no real hot spots, to my untrained eye. At some point, someone(not me) replaced the bulbs in it w/ overwattage ones, and the sockets were totally melted down- 2 bulbs stayed w/ the plastic sockets. so I scavanged the good sockets from the other totally ruined unit, and plan on re-installing this one to see if it may work.

I am not sure if mabbeee the melting smoking was this plastic?? from big bulbs?//? I did have the lights on. doesn't seem likely.


I found a few other things-
the socket which connects to the springythingy on the fender had an old melt-down, on the #4 terminal. I can tell it was a while ago- not yesterday. but maybe a cause to yesterdays smoking?? wish I knew what that terminal was to. 6 wires connect to the box. 5? speeds for the fan??

the other thing was the fuse- which was burned, for the CCU was not a white one, but blue-25amp- which I prolly put in there at some point. I have been meaning to get some more fuses, but could not quite remember why.....


under the hood



the burnt one from the new car- not from yesterday



the board from yesterday next 2 pics. slightly discolored, but not burnt, and not stinky!??


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Old 12-26-2007, 09:12 PM
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Quote:
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sorry to hear about your cold commute. i picked up a sweet used CCU on ebay from a guy in calif. for 100 bucks shipped. i know its kind of a gamble buying these used but he carried a 30 day guarantee on it. i installed it about 3 weeks ago and it works perfect. i think the guys store was called europarts. good luck and happy holidays.... jim
Congrats..........in 12-18 months you'll be buying another one.........of that I can assure you...........it would be a miracle for it to last 3 years.
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  #11  
Old 12-27-2007, 04:22 AM
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I have a CCU board that gets very warm to Hot when in use at just about the same place as the pic in mobetta's last posting. I would sure like to get some good circuit drawings for these things or at least someones call on what each of the little relays controls. I am almost 100% sure that it is one or more of these relays that is causing the overheat and if the controlled device was known, I could unhook that device and or repair it?!?

Anybody got ideas on this?
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Old 12-27-2007, 10:50 AM
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Originally Posted by Lycoming-8 View Post
I would sure like to get some good circuit drawings for these things or at least someones call on what each of the little relays controls.
On the 300D, the K-1 relay controls the footwell flap switchover valve. The K-2, 3 & 4 relays power the blower fan (thru the blower control module) and the main air flap switchover valve.

I would suspect that your blower motor is the culprit. They tend to require more current as a function to time in service.
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Old 12-28-2007, 02:56 AM
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Tango, relative to the board layout, which relay is the K1, K2 etc?

Thanks.
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Old 12-28-2007, 02:49 PM
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If you ask me, that area up at 11:00, sort of in the middle of the board, looks darker than the rest and the solder joints look like they've been heated... that might be the cooked spot. It's certainly large enough to have been smoking and causing mischief.
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  #15  
Old 12-28-2007, 03:51 PM
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Quote:
Originally Posted by Lycoming-8 View Post
Tango, relative to the board layout, which relay is the K1, K2 etc?

Thanks.
Sorry I cannot give an "easy" answer. Per the schematic for a '82 300D, the relays should be connected to the following terminals:

K-1: C-1 pin 3(off or defrost) or 5(except off or defrost)
K-2: C-1 pin 3 only
K-3: C-2 pin 9
K-4: C-1 pin 9

The above connections are for the relay "actuation" circuit only. Hopefully that will allow you to identify the relays.

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