ML320/W164 AC blower not working (error 900E)

[discog]

Hey everyone,

I’m having trouble with the AC on my late 2006 ML320 CDI (W164). The blower stopped working, but the radiator/AC cooler fan is still running, and the AC control panel lights are on. Checked all fuses and ran a code scan which revealed error 900E. I’ve read this could be related to a compressor or electrical fault (maybe low voltage to the compressor or even SAM module issues).

The error text was "Local undervoltage at terminal 30 (voltage below 9v)" - anyone know where this terminal is? I was looking at the compressor but access seems tight. I might get it up on ramps over the weekend and have a poke around from underneath.

Has anyone had a similar experience, and could it be a faulty climate control module? Appreciate any advice - at the moment we have no cooling or heating which is going to be a problem in winter

Thanks in advance!

 

[E55BOF]

Terminal 30 is the standard designation for the 12v+ feed. Corrosion in a connector might well be the cause of the problem; check for resistance in the power feeds to the blower and the compressor.

 

[discog]

Thanks, that's helpful info. Any idea how to get to the blower? I can see that getting to the compressor from underneath seems to be the only way.

 

[E55BOF]

If the blower works when heating is selected, the fault does not lie there. If it doesn't, it is the fan. If so, it's usually the resistor pack that is faulty.

Take a look at this:

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

(Top tip: I had the fan just decide not to play on my R172. I assumed that it would be the resistor pack, or maybe a seized bearing, but when I removed the fresh air intake trunking under the bonnet to see if there was some physical obstruction [there wasn't] and spun the fan, it was free. When I tried it again, it was working fine, and gave no trouble after that.)

 

[discog]

Amazing, thanks for the info. The fan doesn't spin at all, on heating or cooling. Everything else seems normal as far as I can tell (I've not confirmed whether the compressor clutch is engaging or not but I assume so).

I'll have a dig at the weekend but this is great, really gets me on the right track, thanks again

 

[E55BOF]

Glad to help. At the end of the day, it's what this forum is all about.

 

[oldguy57]

If it turns out to be the resistor pack, don't be tempted by the cheap stuff on eBay. Generally don't last long for some reason.