Instrument fuse blowing and alternator stoping

Fascinating, but I just developed the SAME problem today in my 1998 550.

Went for a nice drive, and 6 minutes into the drive I noticed that the gauge cluster was not working. Specifically, oil pressure/temp, water temp, tach, speedo.
Also felt like the power steering was out.

Got a battery emblem on the multifunction display, as well as the suspension warning.

Limped it home, and multimeter showed 11.9 volts at the battery with the engine running.

Discovered a blown #5 fuse, just like you say.

 

I guess the real ? is why does the fuse blow? It could be as simple as the lameo circuit board heating up or?????

 

I have got zero knowledge on Ferrari alternators and how they are wired into the cabling but in an older 911 this is a sign of a failing voltage regulator inside the alternator. And the lowest fuse rating goes first naturally.
MAybe a pointer....

 

Normally the gauge cluster only provides a startup trickle to the alternator through the charging light. That energises (magnetises) the alternator rotor just enough so it can start charging. Because that current goes through a light bulb it can never exceed the bulb and therefore fuse rating. So even if there were a short in the alternator it cannot blow the fuse, it must be something in the cluster or something else that is drawing from the same fuse.
Is this the same fuse for the HVAC panel? Because if it is, then your auxiliary water pump is the culprit. There was a thread on that before. http://www.ferrarichat.com/forum/456-550-575-sponsored-bradan/505726-456m-brethren-can-someone-help-would-save-me-%242-600-a-2.html

 

It sure seems that the first order of business when fuse #5 (the 7.5a instrument fuse) starts blowing, is to pull the right front inner wheel well cover, pull the electrical connector off the auxiliary coolant pump, and see if the fuse still blows.

 

This is one of the MANY reasons why I love this forum (and you guys). I discovered that I was out of 7.5A fuses so I couldn't replace last evening to see if it would blow again. So John, I presumed that the instrument panel and the Servotronic ECU were on fuse 5 (because I seemed to lose power assist in the steering as well). You know for a fact that the aux cooling pump is also on the same circuit?

I read the 550WSM chapter last night but am not good with wiring diagrams.

 

Carl, I thought of your fuse board adventures when I read this also, but I can tell you that the footwell of my car is absolutely virgin with no water ever, very clean looking board, etc. Haven't pulled it apart to look at the back side of the board yet.

 

There are people who know a thing or two....

 

What does this aux pump do. Does it push the coolant into the cabin heater matrix?

 

Pete, it's circumstantial because as we all know, the wiring diagrams are cr*p. What we do know is that when this pump goes bad, it blows the 7.5a fuse, and when the pump is replaced, the 7.5a fuse quits blowing. QED

So the first thing to do is to remove the electrical connector from the pump and see if the fuse quits blowing.....

Yes. Apparently Ferrari or their subcontractor for the heating and A/C system, Diavia, felt the system would be better served by having its own circulation pump rather than using a simple takeoff from the main coolant circuit.

 

So John, I replaced the fuse and the car runs and charges normally.
I am going to take down the fender tonight and look at the pump. Do you think there is any merit to actually removing the pump and disassembling it, looking for corrosion/shorts, etc?

 

Pete/Moorfan: we love you too . There is some merit to it, pumps like that generally fail because of seepage if water past the (simple) seal, corroding the front bearing of the motor after which it burns out. Maybe it came loose on the second try when you replaced the fuse.
If broken, a new pump is probably best although if you can reach the bearing with a proper form of lubrication, it can extend its life significantly even with a leaky seal.
These are Bosch pumps also used on BMW and others of the same era. Partno 0 392 020 034 if I am correct.

 

Lots available on Ebay: 65460300 | eBay

The fix being recommended here is what worked for me last year.

 

Well being that the pump is $50-75 as a non-Ferrari OEM purchase, and based on the fact that I know my pump *looks* old and corroded, I may just replace it. "While I'm in there"
Here's the next question...There are dozens of these Bosch pumps available from Amazon that all look about the same; How critical is it to get the exact model you quoted? I suspect that pump speeds vary between the models?

example:
https://www.amazon.com/Bosch-392020024-Electric-Water-Pump/dp/B001CO17V4/ref=sr_1_fkmr0_1?ie=UTF8&qid=1474907680&sr=8-1-fkmr0&keywords=bosch+0+392+020+034


The model number is slightly different but this one is offered with Prime Shipping! ;-)

 

I would get the exact one used by Ferrari. The others might have slight but important variations. Amazon says the one you quoted does not work on 550
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Well then I won't show anyone the alternator that I have been running on my 550 for 5 years now that comes from a John Deere marine motor

 

Ha. Good to know..

 

Thankfully, I waited until disassembling my right front fender well to order a new pump.

The pump part number in *MY* 550 is 0392020064

What sucks for me is that the listed Bosch pump isn't available from any suppliers anymore. The number cross-references to one of two pumps used in the Maranello. A critical difference is that the pump in my car has the wires coming out of the pump with a connector on the end of them. My connector in the car will be too short and will likely need to be extended. Just a little easy electrical work

I will instead be ordering the previously mentioned pump, 0392020034, which is the OTHER listed pump for the Maranello.
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Hi Pete, good to know, are you now sure that the pump is the problem? If you purchase one of those Bosch connectors and insert the cut the wires from the old pump into it you will have a near-OEM solution.

 

The only significant issue is the cutting off of the alternator. In a pinch has it been verified that you can unplug the pump to kill the short and allow the alternator to work?

 

To the OP, Andre Ouchana, have you been able to diagnose or fix your problem yet?

It would be very good of you to update the thread if/when you do, and tell us what the problem was and what was done to diagnose & fix it.

 

Today a new Bosch pump arrived for me to install in the 550. (Figure 1) To recap, I replaced my #5 7.5a fuse and the car ran normally again while in the garage. I had decided to replace my auxiliary cooling pump "just because".

I did this change quick and dirty...I haven't even gone 200 miles on the new coolant since I changed it and I was not interested in redoing it so soon. Hose clamps solve the problem of coolant leak. (Figure 2)

Once the old pump was out, I had to clip off the old hardwired connections and then plug those back onto the mini-spade connectors of the new pump. This was sealed up with silicone. I also discovered that the pump inlet and outlet port diameters are SMALLER on the -064 pump that was in my car than the port diameters of the new pump. However, it is easy to do a swap of the plastic cap where the ports are, and in the photo the different plastic colors highlight to you where the old cap has been placed on the new pump. The new pump was filled as much as possible with distilled water prior to fully connecting the hoses and releasing the clamps. Hopefully this minimizes the risk of airlock somewhere in the system later on (Figure 3)
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Now that I had the old pump on the bench I wanted to take a look at the innards. There was a lot of evidence of internal contamination of the pump with some corrosion, but I found no liquid inside the electrical section of the pump.

I did not find an obvious short like previous posters have, but feel like this was a quick and minimally expensive thing to replace and rule out in case this fuse wants to continue blowing.
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