'82 300 TD Monovalve Question
 

So, I have been looking around trying to find the answer to this before posting a new post. I couldn't seem to find any definitive answer, so, having said that, here's my question. My 1982 300 TD wagon has stopped producing heat. First thing I tried was to have the monovalve replaced. Unfortunately that didn't solve the problem. I have tested the auxiliary water pump by applying 12 volts via jumpers from the battery and I can hear the pump running, so I'm pretty sure that's not the problem. My question is, can I just replace the pesky monovalve with a 90 degree brass elbow or ball valve? Seems like that would solve all the problems, but I don't want to cause any problems anywhere else in the system.

I replaced the monovalve and aux pump both with a ball valve and I haven't looked back. Plenty of heat if I want it. Given that the monovalve is basically impossible to fix to factory specs at this point, and the aux pump can burn your car to the ground or at the very least prevent the heater from working, it's hard for me to argue for keeping the stock system.

-Rog

Do you have a way to vary the heat as needed from inside the cabin?

Only with the fan. But around here it's either heater weather or it's not, so I've never felt put out by having to pop the hood to switch it. Beats what I had before, which was no heat.

-Rog

What did you use for a ballvalve and fittings? I want to eventually get the original system working properly but for now a stopgap fix will be fine.

I forget the specs, but I just found a valve that fit the hose at the hardware store. I basically plumbed everything straight through and the valve sits approximately where the aux pump used to be. Someone mentioned that using a screw-type valve like you would find on an outdoor faucet would give a finer control of how much heat you'll get, but based on my experiences with a ball valve that seems a bit much. If I don't want heat I just shut the fan off, if I want less I switch it to low speed, if I want to bake a loaf of bread I switch it to defrost.

-Rog

Thanks Rog! I'm gonna go ahead and try it then and see what happens.

Rog,
What kind of pipe and valve did you use? Copper or something else?
I want to keep the aux pump in place (mine is new and on a 2a fuse) and just replace the monovalve for now, so I will need to use an elbow .

The heater hoses are metric but very close to 5/8". A 1/2" Pex ball valve will be perfect fit.

PEX tubing technical specifications and general installation practices

40782 - Webstone 40782 - 1/2" PEX Chrome Plated Mini Ball Valve

It seems like I just used the hoses that were already there. That PEX valve looks way more mint than the one I picked up. Wish I'd found that one.

Here's a couple pics, first of the former monovalve area:

http://i.imgur.com/ctR5r91.jpg

And where the valve sits:

http://i.imgur.com/AG5S4S5.jpg

-Rog

Thanks Rog & Funola,
I'll double check the fitting sizes on the monovalve housing and take a trip to the hardware store soon. I might try to incorporate a filter in the new assembly too. Will post once I get it put together. Using parts for PEX tubing makes a ton of sense since they are barbed fittings. I was worried about using copper fittings and having them come loose.

I think RLeo may have done a ball valve and might have posted pics of his arrangement.... might use ' Marlene' as a search word plus his name.