1991 350SD - No center vents and no AC
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1991 350SD
1991 350SD - No center vents and no AC
Hi All,
2 issues:
*No air operating from center vents. I have removed the push button controls and am not really finding anything behind there. The w123's had several vacuum switches that would electrically open and close to allow vacuum to open a pod. Doesn't seem to be the case here.
Any advise to trouble shooting?
*No AC - Holding a perfect charge, but no power to the compressor clutch. Even when the terminals on the low pressure switch are jumped, the clutch will not engage. I see a relay for the AC, but am not sure where to go from here.
Any wiring diagrams available?
Thanks!
Matt
2 issues:
*No air operating from center vents. I have removed the push button controls and am not really finding anything behind there. The w123's had several vacuum switches that would electrically open and close to allow vacuum to open a pod. Doesn't seem to be the case here.
Any advise to trouble shooting?
*No AC - Holding a perfect charge, but no power to the compressor clutch. Even when the terminals on the low pressure switch are jumped, the clutch will not engage. I see a relay for the AC, but am not sure where to go from here.
Any wiring diagrams available?
Thanks!
Matt
Super Member
Joined: Aug 2005
Posts: 801
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From: Mercerville New Jersey
1991 560SEC Teal 1989 420SEL Ice Blue 1984 500SEC White
Have you checked the 30 amp fuse for the blower? It is not in the fuse box. It is forward of the fuse box, but still in the same bulkhead. You need to pop open the cover to see the fuse.
Member
Joined: Mar 2010
Posts: 94
Likes: 7
From: Houston, TX
2006 E320CDI, 2012 E350 Bluetec, 2013 E350 Bluetec
If the blower motor is functioning, then you do not have vacuum enough to close the center flap. See if you have a high flow of air from the defrost vents. I would first look at the vacuum going to the inside of the car. I think it is the green and red tube. If you have a reading of 20 or more going to the inside, then you have a problem with the center vacuum actuator. You need to remove the right side carpet by the transmission hump and then check the vacuum hoses going into the switch.
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Joined: May 2012
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From: Harbor City, CA
Mercedes-Benz, Porsche, BMW, MINI and more!
Answer
Hi All,
2 issues:
*No air operating from center vents. I have removed the push button controls and am not really finding anything behind there. The w123's had several vacuum switches that would electrically open and close to allow vacuum to open a pod. Doesn't seem to be the case here.
Any advise to trouble shooting?
*No AC - Holding a perfect charge, but no power to the compressor clutch. Even when the terminals on the low pressure switch are jumped, the clutch will not engage. I see a relay for the AC, but am not sure where to go from here.
Any wiring diagrams available?
Thanks!
Matt
2 issues:
*No air operating from center vents. I have removed the push button controls and am not really finding anything behind there. The w123's had several vacuum switches that would electrically open and close to allow vacuum to open a pod. Doesn't seem to be the case here.
Any advise to trouble shooting?
*No AC - Holding a perfect charge, but no power to the compressor clutch. Even when the terminals on the low pressure switch are jumped, the clutch will not engage. I see a relay for the AC, but am not sure where to go from here.
Any wiring diagrams available?
Thanks!
Matt
Here is a link to the free W126 on-line factory service manual supplied by Mercedes Benz.
https://www.startekinfo.com/StarTek/...tedDocId=12253
My first thought is the evaporator temperature sensor has failed = killed all power to the compressor.
MB# 1268301172
http://www.peachparts.com/shopforum/...e-control.html
roy@pelicanparts.com
.
Member
Joined: Mar 2010
Posts: 94
Likes: 7
From: Houston, TX
2006 E320CDI, 2012 E350 Bluetec, 2013 E350 Bluetec
I didn't see the part about the compressor clutch not engaging. have someone start the car and when they do that look at the A/C clutch. Does it engage and then disengage after a few seconds, or does it never engage? it disengages too quickly for you to get out of the car and look at it. You need two people.
If it engages and then disengages, the sensor on the compressor is seeing an incorrect number of rotations. It could be that the drive belt is on incorrectly, yet tightly. Ask me how I know about that....
It is actually possible to route it incorrectly (I actually forget how now), but it was still nice and snug. Compressor sensor sees that and disengages the clutch. Hopefully, it is the same thing for you because it is an easy fix.
If not, you have to start to look at the wiring diagrams and look for power at various stages in the system to see where it is getting stopped.
It sure could be the A/C relay. I've had those go out too.
If it engages and then disengages, the sensor on the compressor is seeing an incorrect number of rotations. It could be that the drive belt is on incorrectly, yet tightly. Ask me how I know about that....
It is actually possible to route it incorrectly (I actually forget how now), but it was still nice and snug. Compressor sensor sees that and disengages the clutch. Hopefully, it is the same thing for you because it is an easy fix.
If not, you have to start to look at the wiring diagrams and look for power at various stages in the system to see where it is getting stopped.
It sure could be the A/C relay. I've had those go out too.
