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Old 04-04-2000, 02:19 AM
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MikeTangas MikeTangas is offline
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Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
The central locking system on my 73 280 SEL stopped working for the passenger side. I determined that the actuators for both passenger doors have holes in the diaphrams, apparently from the lower portion of the window hitting the diaphrams when rolled all the way down. I have ordered replacement actuators and will be installing them as soon as they arrive. In the course of checking out the system I determined the following:

1. With everything hooked up, engine running, the system would pull approx 10 inches Hg.

2. System would bleed off all vaccum from the resevoir within 20 seconds once the engine was shut down.

I believed that the bleed down was due to the bad diaphrams and took the vaccum test a few steps further. Found that the system will:

1. Pull 15 inches Hg with the engine running at idle and the vaccum gauge attached at the check valve, with last leg of the "T" plugged. Hold 15 inches Hg after 15 minutes of with engine shut down. Check valve good.

2. Pull 15 inches Hg at the first "T" with the leg to the cabin plugged. Resevoir tank held 15 inches Hg for 15 minutes with engine shut down. Tank Good.

3. On all night resevoir test, tank held 15 inches Hg for 14 hours, no decernable drop in vaccum. Tank in great shape for 27 years old.

Now for the questions.

Would the bad diaphrams allow for a drop of 5 inches Hg while the engine is running?

Which door do the trunk and fuel door locks operat from? I know the driver's button operates the vaccum switching, but do the trunk/fuel door lock lines come from the right rear?

Also, how many vaccum lines should be running to the fuel door latch? Mine only has one (yellow or off white) which has been capped. The fuel door latch had a 180 degree bent rubber line, which someone cut, coming off the top of that actuator. They then put the cut-off on the lower side of the actuator, leaving it open to atmosphere at both ends. I'm thinking, being at the end of the line so to speak, the fuel door only had one line, the vaccum supply to activate the lock. When the vaccum is removed, atmosphere allows the latch to retract. Am I right?

And lastly, for now, when in the door panel, I hooked up the vaccum gauge to the supply line at the actuator. When teh driver's button was pushed the gauge showed about 1 inch Hg draw. Is that sufficient to cycle the actuators?

I know this is lengthy, but no one has been able to help me yet. With nothing to figure things out, other than what I can surmise from the layout of things, I have tried to explain my finding to the best of my ability.

Thanks to all.

Mike Tangas
73 280 SEL
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