Hello fellow diesel fanatics

I recently did a minor overhaul on the r4 system in my w116: accII upgrade kit from unwired tools, new receiver/dryer, expansion valve, flushed out system etc. There are no vacuum leaks and the system holds pressure just fine with no refrigerant leaks. Pressures are approximately 25 psi on low and 200 psi on high side at 2000 rpm.

The issue: Vents blow cold when traveling under 40 mph but at highway speeds, becomes warm. The air coming from the center flap feels almost like dehumidified air. Very strange indeed. The problem appears to be very counter-intuitive.

Anyone experience anything like this?

Thanks in advance, I'm sweatin my balls off on the highway.

It sounds like the mono valve is opening up, allowing heat into the system....maybe a problem with the unwired kit. Since you've switched to that, I am not able to give much help. Here's is a manual to figure out how the system works. I am not sure, but if you have not replace the sensor tube behind the glove box on the w123..not positive the location on a w116. But that being bad, the system will not be able to sense the interior temperature. Also one problem I am aware of with the unwired kit, is that it will recycle the cabin air....it doesn't operate the fresh air flap. FYI, it is very very easy to have gotten the original system operational again with out the unwire kit.


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

__________________

Sweet! Thanks for the link, much appreciated. The mono valve I verified opens when it should - I had a friend observe its operation as I pushed the various controls.

Regarding the fresh air flap, that is something I was unaware of. Looks like I'm going to be consulting the literature they sent me again. And FYI the original servo was cracked (which is a common problem) so I had no other choice. Are you still using the original servo in your 123???? If you have the same one as the 116 (I'm pretty sure, being a '78) I would be stunned if it was still operational (those things are complete junk).

I was lucky and found the newer aluminum servo on eBay for 50$....my system is 100% operation expect the ac, it needs to be charged or updated....soon I will get that fixed. They aren't really junk as long as you know how the system works and where to find the issues. Even with the unwired kit, you can still have huge issues because of the push button panel and all the vacuum lines and pods. Since your servo cracked, you had to replace it. But typically what happens is the aux water pump freezes and then it kills the computer/amp. If you un freeze the pump and replace the computer....your system will start working again....if you still have the aux pump hooked up, I can promise it is also froze. An also the foam temp sensor tube turns to dust and with out that the system can't tell the temperature of the cabin..

__________________

Hmmmm....on the ACCII system, this would be a bad solder joint in the climate control amplifier. We used to just resolder them.

Mine original 1978 amp worked until last month, when it started to blow warm air from the side vents, cold air from the partially closed center vent and then full cold to the defrost ducting.

I bought a new one from George Murphy at Performance Analysis Company and I am back in business...blowing 32°F on the freeway on LOW at 105°F ambient and 30% humidity.

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership