Which Idle Speed Control unit should be in my euro 1983 500SEC?

[brian_V]

Hi all!

When I bought my 1983 500SEC, it came with two idle control units:

1. One installed, 12/94 date stamp, P/N 002 545 40 32
2. One in the glove box, 51/85 datestamp (51st week of 1985), P/N 002 545 72 32

Obviously both of these postdate the car. My Idle Air/Speed control valve is P/N 000 141 14 25.

The 002 545 40 32 one is for an '84-'85 SEC according to CONTROL UNIT. CONTROL UNITS for 1983 Mercedes 500 SEC. #0025454032. The same site has no results for 002 545 72 32.

002 545 72 32 has results... but few or none in english. Seems to be a part that never made the jump across to NA. I suspect this may be the unit that was in the car when it was imported.

Which I can find reliable info for the US models, it's a bit more obscure with the euro cars. Is either one of these ICUs appropriate for my car?

I'm trying to root out a high idle problem. I tested the idle air control valve:

• At 0V, it's wide open
• At 1.5V, still wide open
• At 3V, it half closes
• At 9V, it's all the way shut

After re-install, I checked the voltage being supplied to the IACV at the connector while the car was idling. The voltage seemed to be pulsing between 0.5 and 1.5 volts, not anywhere near enough to move the valve off the 'wide open' state. I believe this is the root cause of the high idle.

Does anyone know the current I *should* be seeing at the contacts? Is 0.5-1.5V correct and my valve is just finished? Or is this voltage too low, and the fault lies with the (potentially incorrect) idle control unit?

[Dr. Sternschnuppe]

Correct p/n is 002 545 40 32 or 002 545 07 32.

[brian_V]

Originally Posted by Dr. Sternschnuppe

Correct p/n is 002 545 40 32 or 002 545 07 32.

Thank you!

I went through the first few steps of the FSM to diagnose.

I have 12V (actually 12.8V) across the pins of the idle speed adjuster plug when idling. So I plugged it in half way as per the FSM and measured across the pins. I am getting 0.2-0.3V readings... which doesn't match either option.

The FSM tells me I should expect 5V +/- 1V if the regulation is working properly, 0V if it's not. I'm curious what the 0.2-0.3V situation points to, electrically?

I'm wondering if one of my sensor inputs is possibly funky. I'll have to measure them tomorrow.