Maybe (my) Last Heater Thread of the Season

[bhanson]

I am on the tail end of a Winter without heat, for the most part. After replacing all the broken pieces, which included aux. water pump, monovalve (twice - once used one new diaphragm) and repairing one of two Climate Control units, my '83 300D now is heating nicely.

We've had some warm days now, and I find I was TOO successful. I have heat when I don't want it. Even when shut down, with the dial on max cool, I feel heat begin to radiantly cook my toes after a bit of driving. I have no AC system in the car, so that's bad.

So, here's what I have. It's an ACC issue. I have one ACC from the original car, which I've resoldered a burnt board on, that works correctly in all ways, aside from its complete inability to open or close vents. I only get air through the far left and right dash vents. That would solve my heat issue in the Summer. I have another unit, from a 126 chassis, which works correctly in all ways except it doesn't send power to the monovalve when off. I don't know if that's a wiring difference or defect.

So, help me with These choices:

1) Do I look for another ACC that is in fact fully functional and solves all my problems?

2) Do I swap units in the spring and fall?

3) Do I leave the current unit intact and install a manual ball valve for "Heat OFF" in place of the monovalve?

Ben

[Brian Carlton]

Originally Posted by bhanson

So, help me with These choices:

1) Do I look for another ACC that is in fact fully functional and solves all my problems?

2) Do I swap units in the spring and fall?

3) Do I leave the current unit intact and install a manual ball valve for "Heat OFF" in place of the monovalve?

Ben

I would obtain a fully functional unit that, hopefully, solves all your issues.

You definitely should put a 1 amp fuse in the line to the aux. water pump. I had to replace my water pump, and, within several months, the new pump was starting to cause problems to the monovalve. I suspect that the aftermarket pump started to draw too much current, again, and was giving the monovalve some fits (you could hear the monovalve cycling every three seconds or so......not good).

Once you start with Rube Goldberg solutions.......you're definitely on your own.

[tangofox007]

Originally Posted by bhanson

So, here's what I have. It's an ACC issue. I have one ACC from the original car, which I've resoldered a burnt board on, that works correctly in all ways, aside from its complete inability to open or close vents. I only get air through the far left and right dash vents. That would solve my heat issue in the Summer. I have another unit, from a 126 chassis, which works correctly in all ways except it doesn't send power to the monovalve when off. I don't know if that's a wiring difference or defect.

Push button units from different models are not necessarily the same, even though their appearance may suggest that they are.

If I was in your predicament, I think I would put a plug in one of the heater hoses until next winter.

[bhanson]

Brian - The fuse is an EXCELLENT idea since the 123 ACC unit I have has an interesting jumper I put in place over the lowest circuit board where one of the copper strips cooked right off it. It still has issues.

I have read in two places now the only difference between the 123 and 126 controls is the mounting brackets that come on the 123 unit that are unnecessary on the other. It may be that it isn't so, however.

Ben

[Brian Carlton]

Originally Posted by bhanson

I have read in two places now the only difference between the 123 and 126 controls is the mounting brackets that come on the 123 unit that are unnecessary on the other. It may be that it isn't so, however.

Ben

The early W126 units are very similar to the W123, but, I've never attempted to put a W123 unit in the SD.

The later W126 units (post '85) are completely different.

[tangofox007]

Originally Posted by Brian Carlton

The early W126 units are very similar to the W123, but, I've never attempted to put a W123 unit in the SD.

They are not the same. The W126 has an additional flap switchover valve (and associated switch) that does not exist in the W123.

[tangofox007]

Originally Posted by bhanson

I have read in two places now the only difference between the 123 and 126 controls is the mounting brackets that come on the 123 unit that are unnecessary on the other. It may be that it isn't so, however.

Ben

Who ever said that has apparently not looked at the electrical diagrams.

[Brian Carlton]

Originally Posted by tangofox007

They are not the same. The W126 has an additional flap switchover valve (and associated switch) that does not exist in the W123.

Thanks, that's good to know.

Is that additional flap considered the "scoop"??

[dieseldiehard]

Originally Posted by bhanson

I am on the tail end of a Winter without heat, for the most part. After replacing all the broken pieces, which included aux. water pump, monovalve (twice - once used one new diaphragm) and repairing one of two Climate Control units, my '83 300D now is heating nicely.

We've had some warm days now, and I find I was TOO successful. I have heat when I don't want it. Even when shut down, with the dial on max cool, I feel heat begin to radiantly cook my toes after a bit of driving. I have no AC system in the car, so that's bad.

So, here's what I have. It's an ACC issue. I have one ACC from the original car, which I've resoldered a burnt board on, that works correctly in all ways, aside from its complete inability to open or close vents. I only get air through the far left and right dash vents. That would solve my heat issue in the Summer. I have another unit, from a 126 chassis, which works correctly in all ways except it doesn't send power to the monovalve when off. I don't know if that's a wiring difference or defect.

So, help me with These choices:

1) Do I look for another ACC that is in fact fully functional and solves all my problems?

2) Do I swap units in the spring and fall?

3) Do I leave the current unit intact and install a manual ball valve for "Heat OFF" in place of the monovalve?

Ben

Send the PB switch module to be rebuilt OR find a guaranteed good one from a wrecking yard or ebay or somewhere. These fine cars deserve better than a manual ball valve (Please! )

[dieseldiehard]

Originally Posted by dieseldiehard

Send the PB switch module to be rebuilt OR find a guaranteed good one from a wrecking yard or ebay or somewhere. These fine cars deserve better than a manual ball valve (Please! )

Oh, and you could put a set of vise grips on the hose to stop coolant while its being repaired. And unplug the coolant pump during the time being

[tangofox007]

Originally Posted by Brian Carlton

Thanks, that's good to know.

Is that additional flap considered the "scoop"??

The number of flaps is the same (although they don't all correspond in function.) On the 123, the fresh air flap is either open or closed (all or nothing.) On the 126, the fresh/recirculated air flap has a "mid" position (in addition to being fully open or fully closed), so there is an additional switch and actuator to position the flap to allow a mix of cabin and outside air.