Well, I never did pay attention to the warning about the auxiliary water pump.

After finishing five months of work on the SD, it turns out that the blower does not function. After some meticulous checking, the controller is fine, the blower itself is fine and the resistors are fine. The only thing remaining is the CCU.

Remove CCU and pull the bottom plate to find some overheating within the unit. Not a good sign.

Replaced CCU and blower operates normally. But, I only run it for about 30 seconds.

I recall the caveat about the auxiliary water pump. I remove the pump and apply 12V to it from a battery while observing an ammeter. No rotation on the pump and 2.5A draw on the ammeter.

Replace pump and system operates normally.

So, a word to the wise:

Install a 1 amp fuse in the 12V supply to the aux. water pump. Someday it will save you the cost of a CCU. Wish I did,

Added to:
ShopForum > Do It Yourself Links & Resources > DIY Links by Parts Category
Climate Control:

Climate Control:

Cheap insurance.
The CCU is; $Oh $my $GOSH, $$$GASP $$$$$.
Not a happy price in my opinion.

__________________
ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

Thanks Roy.

It's an e-bay remanufactured unit. Price was $80. plus shipping. So far, so good.

I dunno why us Southern folks couldn't just remove the pump and replace it with a bypass hose. I may just try that....

__________________
Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

...or just unplug the stupid thing.

__________________
Never a dull moment at Berry Hill Farm.

hmm ill have to add a fuse to mine and test my spare to make sure its good

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

On the 1986-1991 126s and all 124s, the circuitry is a bit different and a bad aux water pump won't fry your CCU. However, this isn't the case with the pre-1986 126s and 123s. You can unplug or bypass it but the only problem is you'll get lukewarm air at idle. At engine speeds above idle, you won't notice a difference in heat output.

Seems like I read somewhere that if you just unplug it, you have a blockage, therefore basically no heat. I'm thinking you could bypass it and still have enough heat for our balmy climate.

__________________
Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

Believe it or not, I had sufficient heat at 20°F. without a pump and without a blower. Just took about 15 minutes to get comfortable. I removed my coat for the trip back from CT at 32°F. and was quite comfortable.

I am SUPER paranoid now, mine makes noises sometimes, I am buying a fuse holder and 1A fuse on Monday night!!! and wiring it right in!!! Especially since mine is acting flaky on occassion.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Thanks Brian. Maybe I will just unplug it on a trial basis and see what happens.

__________________
Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

Now that's good info, Aaron. I figured that I'd have to go and install the fuse in the SDL's as well. It's great that it can't occur in those vehicles.

Getting to the wiring on the SD is a little tricky. I advise that you remove the battery. Just to the inside of the battery (toward the driver) there will be a plug. This is the plug for the pump. It unsnaps from a holder. Determine which is the 12V lead and put the fuse on the pump side of the plug.

You can't see the pump, or find the wiring to the pump on the SD without taking out half the plumbing between the two firewalls. Naturally, this would require you to remove the middle section of the forward firewall.

Been there done that (we took apart our entire 83 remember) I have personally spent time with each and every part under there...

Here's something horrifying to look at, its the state our 83 is currently in (paint has been redone in this area and sway bar is gone however) The cord for the pump is clearly visible....



Its not all that crowded with everything installed, you can see the pump and plug easily...here's a pic I took of it before we began disassembly....

Attached Thumbnails

   

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

What exactly fries on the CCU?

Is it a little transistor looking thing or is it something else?

I just replaced a mosfet on my ham radio packet modem becuase of some shorting issues in the units past. Pretty easy fix, did it with spare parts, and worked nicely.

The CCU, although complex and small, is still just electronics. It can be fixed by able minds