Instrument fuse blowing and alternator stoping

Pete, if you could measure the DC resistance of the old pump and compare to the new, it might be interesting......

 

And alas, I took the Maranello out for a drive today after replacing the water pump, went to switch on the heater to circulate the coolant through the new pump, and the #5 fuse blew again.

Looks like more troubleshooting is in order.

 

Pete:

If memory serves, my prior finding was that the pump itself did not have a fuse. It seems to run whenever the car is on regardless of the a/c heater being on or off. However it seemed to me that the bad pump caused the a/c ECU to malfunction which then blew the #5 7.5 amp fuse. (That's my recollection..somebody help me out here.) If the pump is disconnected does the fuse still blow? John had suggested trying that.

Terry
Zedtt

 

So I don't have time for full troubleshooting at the moment, but I quickly removed the access panel in the fender well and unplugged the pump. For kicks and giggles I checked both wires of the "car-side" connector to the pump. Both wires are continuous with ground. That doesn't seem right.

Then I tried to turn on the ignition with the pump UNPLUGGED. The fuse pops immediately on turning the key (had the panel opened and watched the fuse pop).

I'm going to dig more deeply into this later tonight/tomorrow. Looks like I will have to try to make sense of those diagrams in the WSM...

 

Disconnect the A/C clutch plug, then retry it. My betting is it's full of oil from weeping cam seals and there's a dead short in the pack. It wipes out the fuse for the exciter feed to the alternator too....

 

pete,

so before you changed the pump it was intermittently causing this problem and now the new pump is 100% a failure? And the fuse blows only when calling for heat? Did I get those 2 things correct or I missed something?

 

Carl, I wasn't very clear in my descriptions, so here is the play by play.
1. Had instrument panel die while driving the other day. Also noticed that power steering was not working at the same time and alternator was not charging the battery.
2. Limped home, checked fuses, found blown #5 fuse. Best I know I had NOT switched on the climate controls during this first drive. Had red battery warning and amber suspension warning on MFD.
3. Replaced #5 fuse, restarted car, idled 5 minutes in the garage and verified alternator voltage at 14.4v, instrument panel working.
4. Read threads online, talking about the heating system pump. Decided to replace mine just because.
5. Went for drive today, about 30 seconds into the drive instrument panel/power steering died again. This SEEMED to be associated with me turning on the heater. Can't say for certain. Again red battery warning and amber suspension warning.
6. Limped back home, found blown #5 fuse again. Replaced fuse, restarted car, fuse blew again.
7. Replaced fuse, and just turned ignition key on without starting motor. Fuse blows as soon as key goes on.

The AC compressor clutch wire is dry and intact. No oil leaks found. Heating system pump looks as it did when I replaced it.

I attempted to read the wiring diagram in the WSM and developed a severe headache

More troubleshooting tomorrow. It seems that the systems involved here are the Instrument panel (excluding fuel gauge and clock) the power steering, and the alternator's ability to charge the battery.

 

It would seem to me that your problem was progressive now to an instant blown fuse. It seems like others with this issue seemed to be the heater pump frozen causing a short or whatever. Just for the heck of it did you unplug the new heater pump to take it out of the circuit and see if the fuse blows?

 

Would resetting the ECU's at this juncture help, hurt or possibly just placebo effect?

 

Since the power steering is apparently on the same circuit, maybe try unplugging the servotronic torque converter on the rack? Perhaps it has an internal short. It would only take a second to try it.

 

Thanks for all the great ideas!
Here is where I am at the moment.

7.5a fuse (#5) blows as soon as the key is turned to its first position. I took the following steps:
1. Unplug coolant pump------fuse still blows
2. Unplug steering rack------fuse still blows
3. Unplug servotronic ECU---fuse still blows

Just for giggles and grins I decided to remove and open up my fuse panel, and OMG...I have the dreaded Fatbillybob fuse panel!!!

This is TERRIBLE electrical work. Piss poor. Having read Carl's thread on fusebox repair, looks like I will be doing the same. I don't know if this has anything to do with my current electrical issue, but I think this needs to be fixed irrespective.
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Somewhere deep in the heart of TX, Brian is rolling his eyes and calling us names...but just trying to help out a brother here.

Anyway here is a thread that discussed an issue similar to current issue..blowing of instrument fuse: http://www.ferrarichat.com/forum/456-550-575-sponsored-bradan/196381-456m-display-gauges-out-reoccurring-blown-fuse-help.html One suggestion within had to do with a lift sensor; not quite sure what it does but here is the Ricambi drawing: ANTI-THEFT ELECTRICAL BOARDS AND DEVICES - Ricambi America, Inc.

One more thing to unplug if it is accessible...

 

Pete, whatever wiring you redo, be sure to get the radiator fans, and possibly the fuel pump circuits off that main board. High current loads have no business being on that shoddily made fuseboard and will only accelerate its demise.

 

Fuseboard has lots of residual flux. It does not look very nice but it does help against oxidation of the tracks. I know, normally the green lacquer takes care of that, but for low-volume manufacturing over 20 years ago, this was not far off the norm.
Only the fans are heavy loaders, the fuel pumps are not that bad. I believe the fusebox problem mostly occurred at where the main power enters the board, so if only the biggest load is offloaded you should be fine? That said, this fusebox does not look damaged to me.

Pity the pump was not the problem, always check assumptions. That lift sensor could be an issue. On a lot of cars, suspension height sensors etc can ingress water and short circuit. Now the short is continuous, it should be fairly easy to find its cause. You can replace the fuse with a 55 or so wattage bulb and unplug things around the car until the short clears.

 

Thank you for all the great help!
Yes, at this point although I don't "like" the way my fusebox looks, I recognize that it is not CURRENTLY the primary problem and doesn't need fixing right away. There is no evidence of arcing on any of the connectors (as seen in other threads). Maybe this is something that I eventually do when I have nothing better to work on.

For now, the biggest issue I have is that I have no good reference to give me information on exactly what is ON circuit #5. And I ran out of 7.5a fuses.

Once I have more fuses, the plans will be to check the system further by disconnecting the AC compressor clutch, the AC ECU (which apparently lives behind the HVAC panel on the drivers side) and then if this is not effective I may need to take out the instrument panel to look for shorts (I hope not)

 

Pete:

I think you can now rule out the aux water pump. It is likely still working if your a/c is working. The #20 fuse (also 7.5A) protects the a/c control unit and that pump is fed by the a/c ECU. To test if the pump is working turn on the heater and check whether the pump is working (with ignition on, engine not running) . Probably best to remove the fender liner panel to do a visual or aural.

Per the WSM, the #5 fuse protects the instruments which are all normally low amp devices. The instruments and warning lights receive signal and inputs from various sensors around the car. One of these many inputs is sending a higher than 7.5A current to the instruments via the fuse and thus is causing the fuse to blow. The tricky part is finding which of the many signals is faulty. It will be trial and error but some sensors are very stable and can be ruled out as a source of high voltage/amp current for example, oil temp, oil pressure, coolant temp, coolant level.

I would start with investigation of suspension ECU, brake/ABS, charging circuit, engine module. However, this is a Ferrari so I would be very cautious about unplugging things unless safe to do so and under proper procedure.

Terry
Zedtt

 

So this evening I went out and bought a fistful of 7.5a fuses and got to work. This vehicle has the standard SRI gold connector kit.

One by one, I unplugged each listed item and then turned the key to see if the fuse blew:
1. Air conditioning compressor clutch wire.
2. Instrument panel wires that are easily accessible from under the dash (3 molex plugs).
3. Anti-lift sensor.
4. HVAC electronic control station.
5. A variety of other interconnects and relays. All one at a time.

No matter what I unplugged, the fuse still blows on turning the key.

I notably have NOT YET unplugged the following items:
1. Solenoid valve adjuster (for the aircon system)---WSM seems to imply that the aircon
system and fuse number 5 have no commonality.
2. Suspension ECU. I probably should do this since I get a "suspension warning" on the
MFD.
3. Alarm ECU.

 

Pete,

You might never find the short by guessing. A blown fuse means you got a short to ground. There are ways to find it with a meter or signal generator type short finder.


for example:
https://www.amazon.com/Tool-Aid-25100-Short-Tester/dp/B000RFLR0U

https://www.amazon.com/FF310-Short-Circuit-Finder-Tracer/dp/B000XVZ8F8


You can you tube how they work.

 

Carl, that's where I am headed next. Otherwise, I could end up disassembling the entire damn car and only find it under the very last panel I remove. I will make sure to post what I find.

 

Pete,

Btw my fusebox kludge is ugly but effective. No joint should be soldered the way I did but it is working

 

So, this evening I finally got the #5 fuse to STOP blowing when the ignition key is turned. Unplugging the regulator harness from the alternator did the trick.

So now I am left with the idea that my voltage regulator is defective. Seems to make sense, as this one is 5 years old and they are not reported to last very long in our cars. I will install a new regulator and see what happens!

 

Nice detective work! Fingers crossed that you've found it.

 

Great news!

 

Well I do not want to tell you I told you so but...

If you live with a 911 you know that a funky rpm meter and x-mas tree on the dash is advance warning of a voltage regulator crapping out.

I consider this an undocumented feature.

A diode could be shorting out as well....

 

I also considered that the regulator plug and harness runs under the exhaust manifold on that side of the engine and is exposed to high heat (although it looks fine on the outside). Will change the regulator first and see what happens.