can i bypass servo like this?
 

i've been looking through lots of posts about bypassing the servo but can't find this answer. i was wondering what would happen if i did it in the most simple way, just connecting the hoses on either side of the servo to each other, with no valve or anything.

just got a 1980 300d to replace my 1978 that got in a fender bender. servo is leaking severely and want to at least do a quick fix so i can get this thing moving.

You will have to install some sort of manual valve, unless you want heat all the time. The servo is, in a sense, an insanely complicated heater control valve.

x2 Just roll the window down to cool you off

so the heat will be on all the time! that doesn't sound so great. maybe i need to put some valve in. then i can at least turn it off in the summer, even if i can't control it from inside.

You can always switch the servo from the 78 to the 80 if it is working.

I currently have mine bypassed while I send my leaking servo out for repair. I have a ball valve in line that I open or close depending on the temperature for a given day.

You can buy a manual ball valve for 5/8" heater hoses, which should work (recall seeing on A Body Mopar Forum - Home of Vintage Mopars like the Dodge Dart and Plymouth Barracuda). If more ambitious, you could rig a cable-operated valve for a 60-70's U.S. car, but a lot of hassle.

I think your best bet is to swap in a manual system from a 240d - I did that on my '80 model coupe and I'm very pleased - goes right in and looks like it belongs there. If the car is your DD you can even keep driving it during the transplant - I drove the coupe a few times for grins with the dash and the console out, the guage cluster held in place (sort of) with a coat hanger, wires everywhere - quite a sight. The job really wasn't too hard I look for D Morrison's writeup with great pics on how to get the a/c evaporator out. By the way, while you're in there, be sure to test the heater coil - my "new" one (from the 240d) leaks a little - would have been so easy to fix when I had it all apart.

Here is a good thread on a bypass of the servo.

If you are pressed for time you can leave out the cable + cable-actuated valve and just put in a ball valve.

http://www.peachparts.com/shopforum/diesel-discussion/205573-early-w123-servo-bypass-described-pics.html

Kudos to unkl300d for the excellent writeup on that.

so i just did a straight bypass because i wanted to get it done fast. i think i'll add a valve later -- or put in the servo from my other car. that servo sort of worked - i could turn on heat and it would be very hot but couldn't control temp, so i had to keep switching it on and off. and ac didn't work, not sure if that's why. it didn't leak though. and there's a chance it was banged in the accident. hmm. probably shouldn't use that one.

i take it there will be no chance of a/c with no servo? i have the service records for this car and it was recharged at some point in the past 10 years. would be nice but not totally necessary.

You don't need the servo in circuit for the AC to work but you will need a way to shut of flow to the heater core such as the aforementioned valve.

I think is the amplfier is bad, the ac will not work.

You may want to read up on it, in this manual....it is quite interesting...

1971 Chrysler Imperial Auto-Temp 2 Service Reference Guide - Session 281