Follow-up status - It was 83 in Chicago yesterday and my AC worked fine. Good evidence that the aux fan fuse blowing indeed had an impact on the temp output of my AC.

I thought about this after my last post also:
The tech bulletin subject line says "Insufficient air conditioning when idling", so I guess that answers that whole question, doesn't it?

Gilly

Thanks Gilly.

I have a '99 ML430 and I just noticed during the last few warm days here in the Chicago area that my AC was not getting cold.

I checked the refrigerant level in the system and that was fine. Noticed that the Aux fans were not blowing when I had the AC on so I checked the #44 fuse. It was blown. Didn't have a 40 amp fuse so I put in another 30 amp to see if the fans would come on. Nothing.

I spoke with service guy at the nearest dealer to determine if the harness recall had been done before I bought the vehicle in '03. Service guy said that the work should have been perfomed and he could not run my vin and see unless the work was done at his dealership.

My question is, whether the recall has been performed or not, if I can't get the aux fans to blow with the 40 amp fuse I plan on testing them with tommorrow, what else could be the problem? Thanks!

If you bought the truck from a MB dealer and the harness was indeed replaced by MB at no charge, they should have it on the Vehicle master inquiry pertaining to your VIN. This work can be done by any MB dealer and the information is updated to a central data base, i.e. any MB dealer can pull the VMI and tell you whether a particular recall has been performed. Your service guy is bsing you. You can tell by checking to see if the old harness is still hanging around the aux fan.

The aux fans only kick in when the temperature is above a certain threshold. You may have a better luck seeing it work when you are stuck in a bumper to bumper traffic or when it is over 90F out. In general, you can tell it's working when you are driving. It generates some whirring sound when the aux fans are on.

That's what I thought Supradupe because in the past this particular dealer has been able to see if any recall was done by entering my vin.

The day after calling that dealer, I called another and the servicewoman entered my vin but told me that no recalls were open on my particular vehicle, so the work had to have been performed. Then it hit me that if the work was done then I should've found a 40amp fuse in #44 and not a 30amp right?

Of course it hasn't been because the old harness is hanging by the fan like you stated. Also, after further checking the system I noticed that the compressor is coming on when the AC button is engaged.

Is it safe to say that once I get this harness replaced that my AC will be blowing cold again and how can I get the work done if these dealers don't want to do it because they won't make any money?

The fuse 44 harness is not a recall item, just a technical service bulletin (TSB) I believe. Therefore, if it was not done under warranty or any form of goodwill, it will not show on the VMI.

Yes, if the old harness is still there and connected, it is not done. If you are handy, this is not a very difficult job DIY. The harness is only 20 some bucks or so. I have harder time finding a 40A fuse from stores like autozone and alike.

If you have good relationship with the dealer, they may goodwill it for you. If you have a big job for them to do, they may thow it in for free. I did it myself, if you follow this thread, you should have ample instructions to complete this job.

Like I said, the aux fans don't kick in when ambient temperature is below certain threshold. That's probably what happened when you tested it with the 40A fuse.

After reading more on the ML's AC in other posts, I decided to add refrigerant despite what the DIY kit gauges showed since the aux fans don't kick in unless there is enough refrigerant in the sytem.

After about 1 minute of adding refrigerant the aux fans came on. Checked inside the truck and it was blowing cold air.

Even though I have not had problems with my 30 amp fan harness, I am still going to buy the part and switch it out. I found that info in a thread as well. Thanks!