Ahoy, Skinnywater!

JB

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I want to thank you again for all the help with my ML320. The materials you sent me and the advice have been priceless.<br /><br />I have another question:<br /><br />My son has a ML320, also. His is a 2000 (mine a 1998). I passed on to him the advice you gave me re: the Aux fan fuse.<br /><br />He usually takes his truck to a third party shop that has a "MB-trained tech". Sure enough, his fuse was blown, too. Like mine, his drivability improved noticably after it was replaced.<br /><br />The tech told him that there is a fan upgrade available, and that the stronger fan uses a 40 amp fuse. His has a 30 amp, like mine.<br /><br />He inquired at the local MB dealer, who claimed that they had already installed the upgraded fan in his truck.<br /><br />I'm sure you can see the contradiction. What is the straight scoop?<br /><br />I would have Emailed this, but I neglected to get your Email addr. into my address book.<br /><br />Thanks again and in advance for your help. :)
 

Skinnywater

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Re: Ahoy, Skinnywater!

It's more then a fan JB. I'll hunt up the appropriate TSI, give you the facts and your options.
 

Skinnywater

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Re: Ahoy, Skinnywater!

JB, the intranet was getting a lot of updates today and I couldn't get a copy of the TSI.<br />I'll give you what I know now since I work 4/10's and I'll not be back until Monday. <br />I still have your email address and I'll send supporting numbers and dates.<br /><br />Since we're in a very hot climate and the A/C system relys on the auxillary fan to additionally cool the condensor. The F44 problem surfaced soon (early '98)at our dealer. Through simple diagnosis it was found that upon initial startup of the auxillary fan a momentary spike of approx. 80 amps would occur in this 30 amp circut. After this momentary spike and the fan is up to speed the current draw would stabilize to 16-20 amps, depending on the amount of debris in the turbulators. The failure of the fuse isn't a short circuit but a gradual stressing of the fuse material. In time the fuse would get a stress crack. This failure in our hot climate occured at the rate of once to twice a year. <br />Subsequent contacts with technical specialists at MB only suggested to replace the fan. However, the new replacements had exactly the same spike. No approved cure was forthcomming. As an automatic proceedure at our dealer, any and all A or B service maintenence on the 163 chassis (ML) recieved a new 30amp fuse. Common complaints or failure was a non issue at our dealer since we did this automatically and many customers weren't even aware the fuse replacement.<br />A couple of years later the failure was common in all locations and climates. Some dealers were (unofficially)installing 40 amp fuses with success. It was my call and judgement to continue with our proceedure rather then an (unofficial) one. Still, so called updated fans still had the same characteristics. Consequently, the ML55 had a massive pulse relay to remedy this situation at production. This is a very expensive relay.<br />And in the model year '03 ML the circuitry was changed and pulse relay was incorporated into design to remedy this situation.<br />Approx. 16 months ago a TSI came out with instructions to remove the old fan harness on '98-'02 ML's and install a larger guage wire harness and increase the fuse size to 40amp. This is the official cure for your ML. <br />However, this work is labor intensive and isn't done automatically. It is done on a case by case basis. It is done free of charge on repeated failures on out of warranty ML's on a case by case basis.<br />You and your son can request this work at the dealer. They may or may not do the work and may or may not charge for it. Again the updated fan does nothing to rectify this condition.<br /><br />If I owned a ML I'd simply buy a box of ATC30's and replace F44 every time I change my oil.<br />As a simple check to tell if F44 has blown, one other consumer shares this fuse. Hit your rear wiper/washer. If it's not working the safe bet is F44 is cracked. ;) <br /><br />This is the "straight scoop."
 

ob

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Re: Ahoy, Skinnywater!

Interesting post skinnywater.I'm not trying to butt in but rather raise a question.You are quite obviously the expert here.Could JB use a clamp around amp probe on the fan lead to confirm this initial startup spike thus ruling out any remote possibility of an intermittent short circuit?
 

JB

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Re: Ahoy, Skinnywater!

Thanks, Skinnywater. :) <br /><br />I look forward to seeing the TSI
 

Skinnywater

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Re: Ahoy, Skinnywater!

Yes he could ob and that would be the diagnosis proceedure.<br />However, if his fan didn't spike to 80 amps on startup, it would also be faulty. <br />The point is, a brand new out of the box, made yesterday fan, spikes to 80amps on a 30amp circuit.
 

Skinnywater

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Re: Ahoy, Skinnywater!

Sorry for the delay JB. You have mail.<br /><br />If it isn't parked in the Service drive or have a repair order on it, I tend to forget. ;)
 

JB

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Re: Ahoy, Skinnywater!

Thanks, Skinny.<br /><br />I'll get this done before Spring. :)
 
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