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Old 08-16-2007, 10:55 AM
Registered User
Join Date: Aug 2007
Posts: 1
1983 380SL Idle Valve - not getting any power

Hello Folks,

I own a 1983 380SL, recently a few days ago my car started idle very high approx 2000 rpm's. I have been doing some tinkering around and have discovered that the idle valve is not receiving any power.

I have checked the fuse, and it seems to be fine, I was wondering if anyone could assist me here. My next bet is that the Electronic Idle box which is located behind the glove box could be gone.

Before I spend the 250.00 could someone give me some advise??

I appreciate it very much!


Zeester - Ottawa CANADA
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Old 08-16-2007, 12:42 PM
Registered User
Join Date: Apr 2005
Location: Rockville MD
Posts: 833
Check the connectors on the idle control module. The one on mine came loose, causing the same problem.
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma
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Old 08-16-2007, 09:47 PM
Super Moderator
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
If you are not getting anything at the valve, the test is to remove the control unit and bridge pin 1 to pin 2 and pin 4 to pin 5 simultaneously for a short time. If the valve clicks, then replace the control unit.

You could also do a Search and find my recent post on how to make a restrictor that will slow your idle down for cheap.
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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Old 08-21-2007, 02:59 AM
Registered User
Join Date: Jun 2002
Location: Melbourne, Australia
Posts: 91
If you find the control unit is at fault and have access to a soldering iron, or know someone with some knowledge in electronics.
Resolder all the joints on the small rectangular plastic capasitors, usually red, green and somtimes orange in color.

As with most control module in these cars cruse control, idle control etc.
These capacitors have very bad joints on there leeds, I feel they must have been slighly oxidised before they were installed and the flux in the solder was not enough to clean them. The bad joint is very hard to spot with the naked eye, but becomes apparent under a microscope when you tug on the component (you can sometimes pull it streight of the board)

Also ther is a large 3w resistor on board that can run warm and can dry the solder joints out on its leeds creating an unreliable connection.

The the power to the ICV is square wave or pulsed DC at approx 512HZ, that will vary it's pulse duration as the engine warms up or the A/C or Neutral switch is engaged. So if you mesure the voltage with a digital meter it will average it and seem quite low in value not the full 12V as you may expect.

The ICV valves themselves can gum up causing a high idle, if your lucky you can spray CRC or better yet some carby cleaner repeatedly in it oriffices let it soak for a while blow it out and give it another try.

Good luck


Last edited by Damian; 08-21-2007 at 07:13 PM. Reason: Wrong frequency of ICV drive
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