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  #1  
Old 01-12-2010, 09:04 PM
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What purpose does the swichover valve serve?

What adjustments can you do with the switchover valve? It's a vacuum and electro switch on the firewall near the brake booster only on the outer firewall. It has an adjustment screw on the top.

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Old 01-12-2010, 09:15 PM
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The switchover valve does not have an adjustment screw on it, at least all the ones I've seen don't.
It's goal in life is to slow down/shut off fuel to the IP if the turbo spools up too much pressure, I'm thinking a redundant system for the waste gate.
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Old 01-12-2010, 09:20 PM
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There's a little thumb screw thing on the top

Well at least it looks like a thumb screw. You can turn it cw and ccw. I just saw a vacuum line going to it and thought it was an adjustment for idle or shift. Thanks for the reply.
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Old 01-12-2010, 09:23 PM
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Okay, what car and can you post pics?
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Old 01-12-2010, 09:27 PM
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It's an 83 300SD

It's an 83 300SD. I am not able to post a pic just yet.
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Press 1 to continue in English, Press 2 to disconnect and call back when you learn to speak English.
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Old 01-12-2010, 09:29 PM
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Is your valve round or square?
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Old 01-12-2010, 09:33 PM
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Well, slap me silly!
Damn if there ain't an adjustment knob, never noticed it. And certainly don't know what to do with it.
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Old 01-12-2010, 09:33 PM
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It's square

It's square with 2 wires on a plug on the bottom and a vacuum line behind those wires.
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1983 300 SD. 157K.
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2007 Toyota Tundra
2007 Toyota 4 Runner
1993 Toyota Sequoia
Press 1 to continue in English, Press 2 to disconnect and call back when you learn to speak English.
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Old 01-12-2010, 09:49 PM
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I can't find any adjustment procedures/reasons in the FSM. It's #21 in the pic.
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Old 01-12-2010, 09:55 PM
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Steve Brotherton , Import car

Steve wrote a real good article about MB transmissions and he refered to it but only in saying it sends a signal to an aneroid valve. I was jsu wondering.
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1983 300 SD. 157K.
1964 Studebaker GT Hawk
1972 Corvette, Bought new
2007 Toyota Tundra
2007 Toyota 4 Runner
1993 Toyota Sequoia
Press 1 to continue in English, Press 2 to disconnect and call back when you learn to speak English.
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Old 01-12-2010, 09:56 PM
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I don't think that is an adjustment. It is merely a cap for the vent. Someone correct me if I'm wrong.
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Old 01-12-2010, 10:07 PM
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It's a vent. That is for overboost protection, if the boost sensor is tripped it closes that valve and vents the pressure at the ALDA and therefore cuts fuel. Safety feature, and why the car will surge badly at WOT if the wastegate is disconnected.
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Old 01-12-2010, 10:22 PM
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Thanks folks.
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Old 01-23-2010, 07:19 PM
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There's a round switchover valve too that I think is part of the 124 HVAC system. What's that one do?
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Old 01-23-2010, 09:43 PM
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^ I would think the same thing.

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