| Author |
Message |
Mike Florio (Mike_in_nevada)
New member
Username: Mike_in_nevada
Post Number: 45
Registered: 6-2003
| | Posted on Tuesday, September 16, 2003 - 10:25 am: | |
Dan - There are three pins coming out of the bottom of the flasher relay that plug into the socket. They are labeled 49a, 49 and 31. The one labeled 31 is the ground pin. Sometimes the numbers are embossed on the bottom of the relay where the pins come out. If you can figure out which one is pin 31, the corresponding socket should be a solid ground.
Those wires under the seat are for the "driver's seat occupied" circuit. There is also one under the passenger seat. It is wired into the seatbelt buzzer, which most people disconnected. These circuits are also grounded the same place as the tach ground. Other circuits on this ground path include the ash tray light, the cig. lighter, window control switches, and the aux fan relay, as well as most of the other instruments. That's why I think you have a bad ground - the interplay with all these instruments can give a lot of interesting symptoms.
If you find the ground wire for the tach, don't just cut it off and run it to ground. Splice in a ground wire and ground the whole set of circuits. Ground is Ground - you may clear up a lot of problems. If everything works after that, I would leave the new ground in place as a semi-permanent fix. |
g dan (Nsk)
New member
Username: Nsk
Post Number: 6
Registered: 9-2003
| | Posted on Tuesday, September 16, 2003 - 2:32 am: | |
Malcom, I have not. Assuming that works, is it safe to leave it in place?
Overall, based on my limited knowledge/experience,
I am inclined to think it isn't necessarily the tach since
the speedometer seems to be affected as well, albeit much more rarely and under slightly different circumstances.
While taking things apart I have found an
alarm of some sort under the driver's seat.
It doesn't appear to be working although it is wired. Will be taking this out.
If there is a bad ground anywhere in the system can it effect any other part of the system?
Speaking of bouncing gauges, while cleaning
the engine compartment light, I must have touched one of the gas gauge wires. It was vibrating with every bump, in an incredibly accurate fashion, like a spring.
Fun -> connect the radio to all gauges. Voila, instant screen saver for one's Ferrari.
>measure pin 31 to ground
Mike, I would still be interested to understand
what pin 31 is.
Thanks
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Malcolm West (Ferrari_uk_tech)
Junior Member
Username: Ferrari_uk_tech
Post Number: 129
Registered: 7-2003
| | Posted on Monday, September 15, 2003 - 6:30 am: | |
Dan,
Have you tried running a seperate ground wire directly from the tachometer to a known ground, if this makes no difference then the fault isn't a grounding problem (although from your descriptions it sounds like it is)
MW |
g dan (Nsk)
New member
Username: Nsk
Post Number: 5
Registered: 9-2003
| | Posted on Saturday, September 13, 2003 - 1:10 pm: | |
Further investigation ...
Turning the lights on also affects the tach.
The fan speed switch does as well.
The hazards do not.
Two thin black wires near the ignition
connect to white/red stripe wires.
The connections have fuse like covers on them. These wires appear to terminate into the key buzzer
fuse.
A black wire coming out of the ignition,
has a 30 amp fuse attached (it is OK). This wire is tapped into by a purple wire which
appears to be a later addition. It goes to the radio and is grounded by the fuse box.
There are several other black wires under the dash which are a bit difficult to follow without
loosening a lot of wires up. Are all black wires supposed to be ground? Is there a common ground
area where all black wires meet?
>Remove the flasher relay in the relay box
>and measure pin 31 to ground
Could you tell me which is pin 31?
Although the problem appears to be systemic,
given that the fan speed and lights affect the tach, no?
Unlikely it is the cause, but the relays for the key buzzer and seat belts have been removed.
When installing the radio noticed the "illumination" and "backup/constant power" wires were dead.
Before replacing the radio,
turning the lights on used to momentarily affect the radio. The old radio had the "illumination" and
"backup/constant power" wires attached. The new one does not
and it is not affected when turning the lights on.
Thanks again for your assistance.
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Mike Florio (Mike_in_nevada)
New member
Username: Mike_in_nevada
Post Number: 41
Registered: 6-2003
| | Posted on Saturday, September 13, 2003 - 10:13 am: | |
Now that really sounds like a floating ground to me. According to the wiring diagram there are 2 ganged chassis grounds in the dash area - one with 5 wires, and one with 3 wires. Each then daisy-chains to other circuits. The ground for the tach looks like it is the same circuit as the flashers and turn signal relay.
Remove the flasher relay in the relay box and measure pin 31 to ground. I'm willing to bet you will find it not grounded. The ground wires are black. Trace one or two black wires to find the two places behind the dash where they attach to the body, and clean up/tighten the connection. |
g dan (Nsk)
New member
Username: Nsk
Post Number: 4
Registered: 9-2003
| | Posted on Saturday, September 13, 2003 - 2:05 am: | |
>a blown fuse in one circuit,
If you mean on the fuse panel, they are OK.
Regarding pounding, I'll try it since at times
immediately after starting it without pressing
the accelerator, I can get the tach to "dance"
in rhythm with the turn signal.
Thank you for the suggestions. |
Skip Williamson (Darolls)
New member
Username: Darolls
Post Number: 49
Registered: 7-2003
| | Posted on Saturday, September 13, 2003 - 1:19 am: | |
Dan-
Sounds like a bad ground.
If not, a blown fuse in one circuit, can cause anomalies to occur in other circuits through feedback.
To test for a bad or weak ground, try the old GM test. When the problem occurs, start pounding on the dash in different areas. If the problem corrects itself when you start beating on a section of the dash, that's probably where the problem is.
I'm not joking, that's how I found a bad ground in one of my F-cars! |
g dan (Nsk)
New member
Username: Nsk
Post Number: 3
Registered: 9-2003
| | Posted on Saturday, September 13, 2003 - 12:39 am: | |
Mike, thanks.
Ferrari dealer indicates they inspected the ground wires and they looked OK (not a guarantee but ...).
Since it oscillates when I press the brake pedal or switch the turn signals on (intermittently and only noticeable above 3-4k rpm) shouldn't the problematic wires be located where the turn signals and brake lights meet? Perhaps somewhere in the vicinity of the tach wire as it leaves the ignition box? |
Mike Florio (Mike_in_nevada)
New member
Username: Mike_in_nevada
Post Number: 35
Registered: 6-2003
| | Posted on Thursday, September 11, 2003 - 10:10 pm: | |
Dan:
I would look at the common ground behind the instrument panel. Trace a few ground wires and you should find a common termination. It sounds like a loose ground connection or a broken ground wire.
As for the door light, the whole unit pulls straight out of the door. Grab the chrome outside bezel with your fingernails and pull. You can get at the bulb without any more disassembly. |
g dan (Nsk)
New member
Username: Nsk
Post Number: 1
Registered: 9-2003
| | Posted on Thursday, September 11, 2003 - 6:58 pm: | |
1. The tachometer jumps all over the place,
intermittently, when pressing the brake pedal,
or switching the turn signal on. Appears to be
directly proportional to the rpms, ie. higher rpms, more up / and down frantic oscillation.
Ferrari dealer recommended cleaning the main harness going to the dash.
They did so, and it appeared to have resolved the problem.
However, after ~1h driving home, the problem has returned, as before except ... the
speedometer also bounced up a bit, at idle.
2. Would like to replace one of the interior lights' bulbs (on the door). Does anyone know
if/how the lens is removable without taking the door panel off?
Thanks, Dan
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