W114 / W115 - Retrofitted new Sanden A/C but won't turn on - Mercedes-Benz Forum

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post #1 of 26 (permalink) Old 07-22-2015, 04:11 PM Thread Starter
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W114 / W115 - Retrofitted new Sanden A/C but won't turn on

Alright guys, I could really use your help! I just spent the last week carefully removing the old factory A/C lines and York compressor, refitting the system with new lines and a rotary Sanden SD5H compressor. I'm no dummy but I can say I've never attempted A/C work before now. I took my time and ensured each and every fitting was nice and tight. Everything that came out went back into the car with new components.


New items: lines, compressor, condenser, dryer, expansion valve

With all the install work done, I decided to try to turn on the system BEFORE I drew down the air and added refrigerant. The a/c didn't work in the car when I bought it. The fan never came on. When I turn the switch on the dash, I don't hear the 'hissing' sound other posters have mentioned it should make as the system engages. Nothing but silence and a dead green light on the console.

I've checked the fuses to the right of the dryer (2 fuse boxes mounted to the firewall of the car). Fuses are good. I'm not sure if this is enough to go on. I'm happy to supply images or provide additional details. It's 'fires of hell' hot down here in Tampa and I've got to get this A/C sorted out. Any and all help is much appreciated. Thanks!
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post #2 of 26 (permalink) Old 07-22-2015, 04:37 PM Thread Starter
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Possibly a problem? I see there is one wire (with 2 male/female connections) attached to the same loom that connects to the dryer. It clearly was supposed to plug into something but there doesn't seem to be any logical location for them to go. Any help would be appreciated

[IMG][/IMG]

Here is the wire, moved over to the opposite end of its reach:

[IMG][/IMG]

Man, I sure could use a break and have some simple solution to this problem. This A/C system has really given me a savage beating and has rewarded my considerable efforts with absolutely nothing.
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post #3 of 26 (permalink) Old 07-22-2015, 05:54 PM
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Hey Dave, sorry to see your having these AC issues. I too am in the same boat. I have been needing to do the complete AC replacement on my 72 250, I am forced to drive the car at night or early morning when the temp is a lot cooler. Here in the high desert, its like driving a green house with all of that glass on the car and rolling the windows down only sucks in the smell of exhaust.

As for those wires, to me, those look like the wires that activate the fuel shut off solenoids on the carburetors. Can you tell us what carbs you are running in your engine?
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post #4 of 26 (permalink) Old 07-22-2015, 06:17 PM Thread Starter
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Originally Posted by Luna Gaudi's 72 250 View Post
I am forced to drive the car at night or early morning when the temp is a lot cooler. Here in the high desert, its like driving a green house with all of that glass on the car.

As for those wires, to me, those look like the wires that activate the fuel shut off solenoids on the carburetors. Can you tell us what carbs you are running in your engine?
Ah, you see, there is always someone who has it worse than you! You, my friend, win the 'Suffer for Your Cause' award! I have the dual Redline Weber kit on my car. Those two wires don't reach that far across the engine bay. It's crazy. No earthly idea where they went off to.

I'm wondering if maybe just ditching the vacuum operated system might not be a better approach. A Vintage Air unit might be able to be retrofitted under the dash and inside the console. I can dream
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post #5 of 26 (permalink) Old 07-22-2015, 06:25 PM Thread Starter
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Originally Posted by Luna Gaudi's 72 250 View Post
I too am in the same boat. I have been needing to do the complete AC replacement on my 72 250
An interesting aside for you to consider is all of the original Aeroquip hose ends that came stock on your a/c system are reusable. That means you can save piles of cash on having custom hoses made for your car. I just ordered a $50 hose kit from Ebay (it was Aeroquip brand), a $20 dryer, a $40 condenser, got my genuine Sanden compressor new out of Canada of all places LOL! - it was only $75. I really got lucky with the compressor. All in, once you count the cost of the ancillary items like refrigerant, the Harbor Freight evacuator, some gauges, etc... I'm into it for about $325. That and a ton of time spent working, cursing, then working some more.

Once this gets resolved, I'm going to be feeling pretty darn good about myself. Until then, I (and my wife) hold myself suspect.
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post #6 of 26 (permalink) Old 07-22-2015, 07:34 PM
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Wow not a bad price for what you bought. I was figuring it was going to run me about 1100.00 and then still not sure if everything would still work properly.

As for the wires, that is the length that they are. The shut off solenoid has a wire that is about 18" in length that hooks up to those ends that you are pointing out. I know the zenith carbs like I have, use the shut offs, I am guessing that your webbers do not. I just double checked mine. They are two female ends. I am wondering if the plastic on one of yours was brittle and chipped off exposing the metal connector. On the one with the metal connector exposed, is the metal connector solid or hollow?

Quote:
Ah, you see, there is always someone who has it worse than you! You, my friend, win the 'Suffer for Your Cause' award!
lol, thanks for the award, but i must respectfully decline, I drive the porsche on the hot days which has the cold AC.

Last edited by Luna Gaudi's 72 250; 07-22-2015 at 07:50 PM.
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post #7 of 26 (permalink) Old 07-23-2015, 09:08 AM Thread Starter
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Originally Posted by Luna Gaudi's 72 250 View Post
As for the wires, that is the length that they are. The shut off solenoid has a wire that is about 18" in length that hooks up to those ends that you are pointing out. I know the zenith carbs like I have, use the shut offs, I am guessing that your webbers do not. I just double checked mine. They are two female ends. I am wondering if the plastic on one of yours was brittle and chipped off exposing the metal connector. On the one with the metal connector exposed, is the metal connector solid or hollow?
You nailed it with that wire. The one side that appeared male just had the plastic jacket missing. Seems like the wire just doesn't stretch very far. I was hoping this was some sort of easy clue that would lead to a functioning a/c system


Quote:
Originally Posted by Luna Gaudi's 72 250 View Post
lol, thanks for the award, but i must respectfully decline, I drive the porsche on the hot days which has the cold AC.
Well-played, Sir! That is definitely a practical solution but hopefully there is an answer to the problem that troubles us. I'm going to continue combing the web for some info. Also will apply Occam's razor and start with the simplest causes and work my way in the direction of the more exotic possibilities. It's probably something extremely minor and we'll all have a good laugh about it when it's over.

Cheers!

[IMG][/IMG]
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post #8 of 26 (permalink) Old 07-23-2015, 07:45 PM
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It would appear you have a pressure switch on your receiver/dryer. That switch usually disables the clutch on low pressure to protect it. Clutch will not engage without freon in system.
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post #9 of 26 (permalink) Old 07-23-2015, 10:00 PM Thread Starter
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@TZ_280SEL I didn't realize this part about the sensor. I'm going to look into that. The question I have is that the A/C fan doesn't turn, the green light doesn't come on (next to the 'C-O-L-D-E-R' knob) and the entire thing acts just as dead as it ever did prior to all this effort and retrofitting.

Thanks for your input. I hope to find something good with disconnecting those sensor wires on the dryer.
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post #10 of 26 (permalink) Old 07-24-2015, 06:55 AM
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My W108 had the same issue. It was the blower switch below the dash. On my car, the original blower switch has 12V into it, and it provides variable voltage out for the blower speed and also a switched 12V for the compressor. My switch fell apart in my hand when I pulled it out. Had to replace it with a new switch of similar design (could not find an original) that has high, medium, low instead of continuously variable.

If you have access to the back of that switch, make sure you have 12V to the switch and then make sure you have voltage out when you try to turn on the system.
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