Rich W

I know this is not a new thing, but I have researched the archives and come up a little short on this combination.

First, the background: I'd noticed that the driver's side (LHD) vents blew cold air when the temperature **** was set to full heat. After reading Roly Baldwin's excellent article, I pulled the cover and tested Servo 4 (numbered from left to right while facing the car from the trunk). It was not functioning. I repaired it per Roly's directions, and it operated.

But the operation is wrong!

It was stuck in the 5 o'clock (full shut - cold air) position. After conducting repairs, it now goes to the 12 o'clock position when the temperature dial is turned to cold, and the 5 o'clock position when the dial is turned to hot.

Also, the driver's side windshield vents are barely blowing any air, while the passenger's side vents function marvelously. The center and side vents work fine when the ***** are selected to blow air from them.

I'm concerned my CCU has decided to take a long vacation without me.

Any ideas?

Rich W

...another tidbit.

When the temperature dial is selected to cold, cold air comes out the center and side vents. When its selected to hot, cold air comes out the center and side vents. When the temperature dial is selected to the midrange, warm/hot air comes out the vents.

My air conditioner does not work due to the infamous leak, so I've removed the air conditioner compressor belt (it's been off for quite a while, long before these problems manifested themselves).

Sorry about the omission.

Adrian

Dear Rich,
I would be almost 100% sure that your problems come from the attempted repair of the servo valve. Thse repairs have a very low reliability rate. I would not recommend you waste money elsewhere until you know 100% that the servo valve is working correctly.
This can be achieved by;
a). Purchasing a new one or
b). Swapping the left and right servo valves over.
One danger of trying to repair these servo valves is that they are powered and driven by the control unit. If you make a failure and short out the power you will fry the control unit.
Ciao,
Adrian
964C4

Rich W

Adrian,

Thank you for the reply. The symptoms were the same prior to attempting repairs, so it would appear that while the servo unit APPEARS to be working, nothing has changed.

I will swap servo units around and post results.

Adrian

Dear Rich,
The motor maybe moving the arm but have you checked that;
a). The motor is providing the same torque as the pax side and
b). It is actually moving the mixing chamber flapper valve. Not the servo valve but the flapper valve. The mixing chamber forms part of the blower assembly by the way.
Ciao,
Adrian
964C4

Rich W

Thanks Adrian.

More things to check... I might have this diagnosed by 2006 given my current schedule!

Rich W

One problem fixed!

Turns out I'd hooked up the operating arm about 120 degrees out, which is why the arm went to 12 o'clock (w/o the rod hooked to it). Now that I've fixed that oversight, the #2 servo works fine.

Now it's off to tackle the #5 servo since the windscreen vents on the driver's side are still not functioning properly.

Adrian

Dear Rich,
Please explain this No 5 servo business. The windshield vents are not servo controlled. They are pressure differential controlled. The trouble is I have no idea (well I do but speculation is not in order here) which servo you are talking about.
None of the vents as such are servo operated they are all differential pressure flapper valves. The fresh air, defrost and footwell servo valves operate a single flapper valve and then air pressure is used to do the rest. You could call these flapper valves, air pressure redirection valves.
Ciao,
Adrian
964C4

Rich W

Adrian,

I apologize if I have created any confusion in my descriptions.

Using Roly Baldwin's article as a guide, the servo motors are numbered 1 through 5, with number 5 on the right as viewed from the front of the car, looking into the trunk (boot).

Roly refers to the upper HVAC slide control as directing air to the windscreen, and further identifies it with servo 5. I've observed that this servo does not operate. I disconnected the metal linkage and manipulated it, but there appears to be no change on air flow - indeed, in one case it appeared all airflow stopped.

Is this sufficiently descriptive? I have not photgraphed the location in question, but would gladly do so.

Rich

Roly Baldwin

Rich,

I'm sorry I've caused you some confusion and also for the error in the article (it's fixed now). My labelling of servos 1 and 5 was incorrect. 1 should be 5 and vice versa.

I'm not sure I understand exactly what problem remains but these pictures, showing the distribution unit removed from the car, might help:

FRESH AIR VENT
In this pic, I'm operating the no 3 (middle) servo's linkage.


FOOTWELL VENTS
Here, it's the no 5 (far right looking from the front) servo's linkage.


SCREEN VENTS
In this one, the linkage attached to no 1 (far left looking from the front) servo has been rotated.

Rich W

Thanks for the clarification Roly. I might have started working on the wrong servo! Fortunately, work has kept me busy enough that I have not yet undertaken that project.

Rich W

Roly,

One question remains - I just went to John Miles' site, and the article appears to be the same as I used to diagnose and repair my servos. Therefore, the number 5 servo is in front of the driver in LHD models. Is that correct?

Roly Baldwin

Rich,

The servos are positioned in the same place on LHD and RHD cars. No 5 would be in front of the driver in a LHD.

Rich W

OK Roly. I moved the vent control on the CCU, and Servo 5 didn't budge. And I can't figure out how to remove it!

Any help?

Randall G.

I thought you RSA guys didn't care about weight-adding baggage such as HVAC?