testing of idle control unit 004 545 10 32 - PeachParts Mercedes-Benz Forum

william.wood · #1 10-18-2005, 03:56 PM

i have a 1988 420SEL 114km that idles way too fast 1,800 rpm. some of the answers to my previous posts and threads have led me to suspect the IDLE CONTROL UNIT but at $350 from the local BENZ monopoly i would like to some how test the unit before laying out that kind of coin to replace it.[i just today took it to the local benz dealer to have the ICU checked out and all they wanted to do was order me a new one] is it possible to test the IDLE CONTROL UNIT? part no. 004 545 10 32 or by doing some sort of continuity or ohms readings between the pins on the unit itself?

i have an old chiltons service manual for MB imports with general Q&A for all import cars .. and for 8 cylinder MB cars it says to check for continuity on pins 4 and 2 to the idle speed control valve ..[ISCV], but i traced my [black & blk/ylw] leads from the ISCV to pins 6 and 7 on my ICU [idle control unit] socket, so that isn't right. i also know that the ISCV works because if i take a 9v transitor radio battery and place it directly across the ISCV contacts, the idle drops way down. is this enough of a test to warrant replacing the ICU?

also other readings are as follows: the oil temp sensor never fully opens or closes. cold, 50F-70F, it reads about 450 ohms, warm/hot it reads about 750 ohms, the 2 pronged fluid/coolant temp sensor is about 4k ohms cold 50F-70F.

i also have bought 3 different 2cd-rom sets of supposedly service/manuals off of the internet specifically for MB's and none have anything about testing parts, or testing proceedures, etc. all they do is show where items or parts are located and what they are called etc..... they really don't offer any sort of helpful service knowledge or testing procedures.
william.wood wmwood@comcast.net

tvpierce · #2 10-18-2005, 10:07 PM

Sorry... can't help you with testing. Hopefully someone else will chime in.

But if it turns out that you indeed need one, you can get one right here (from MercedesShop) at this link:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1LQ19OZGC1N21BAJX7&year=1988&make=MB&model=420-SEL-001&category=C&part=Idle+Control+Unit

You'll save youself $50 and you'll be supporting the folks who make this forum possible. (FYI: Shipping is free on orders over $100)

Good luck.

Jeff Pierce