coolant temp spikes when lights are turned on...
- Thread starter Stangtamer
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Grounds are important to any electrical system, and especially to
computers.
1.) The main power ground is from engine block to battery: it is
the power ground for the starter & alternator.
2.) The secondary power ground is between the back of the
intake manifold and the driver's side firewall. It is often missing or
loose. It supplies ground for the alternator, A/C compressor
clutch and other electrical accessories such as the gauges.
Any car that has a 3G or high output current alternator needs
a 4 gauge ground wire running from the block to the chassis
ground where the battery pigtail ground connects.
The 3G has a 130 amp capacity, so you wire the power side
with 4 gauge wire. It stands to reason that the ground side
handles just a much current, so it needs to be 4 gauge too.
Picture courtesy timewarped1972
3.) The computer has its own dedicated power ground that
comes off the ground pigtail on the battery ground wire. Due to
it's proximity to the battery, it may become corroded by acid
fumes from the battery. It is a black cylinder about 2 1/2" long
by 1" diameter with a black/lt green wire.You'll find it up next to
the starter solenoid where the wire goes into the wiring harness
4.) All the sensors have a common separate ground. This
includes the TPS, ACT, EGE, BAP, & VSS sensors.
5.) The O2 sensor heaters have their own ground (HEGO ground)
coming from the computer. This is different and separate from
the O2 sensor ground. It is in the fuel injector wiring harness and
comes out under the throttle body. It gets connected to a
manifold or head bolt.
6.) The TFI module has 2 grounds: one for the foil shield around
the wires and another for the module itself. The TFI module
ground terminates inside the computer.
7.) The computer takes the shield ground for the TFI module and
runs it from pin 20 to the chassis near the computer.
8.) The computer's main power ground (the one that comes from
the battery ground wire) uses pins 40 & 60 for all the things it
controls internally.
See http://www.fluke.com/application_notes/automotive/circuit.asp?AGID=1&SID=103#volt
for help troubleshooting voltage drops across grounds
Extra grounds are like the reserve parachute for a sky diver.
If the main one fails, there is always your reserve.
The best plan is to have all the grounds meet at one central spot
and connect together there. That eliminates any voltage drops
from grounds connected at different places. A voltage drop
between the computer ground and the alternator power ground will effectively
reduce the voltage available to the computer by the amount of the drop.
computers.
1.) The main power ground is from engine block to battery: it is
the power ground for the starter & alternator.
2.) The secondary power ground is between the back of the
intake manifold and the driver's side firewall. It is often missing or
loose. It supplies ground for the alternator, A/C compressor
clutch and other electrical accessories such as the gauges.
Any car that has a 3G or high output current alternator needs
a 4 gauge ground wire running from the block to the chassis
ground where the battery pigtail ground connects.
The 3G has a 130 amp capacity, so you wire the power side
with 4 gauge wire. It stands to reason that the ground side
handles just a much current, so it needs to be 4 gauge too.
Picture courtesy timewarped1972
3.) The computer has its own dedicated power ground that
comes off the ground pigtail on the battery ground wire. Due to
it's proximity to the battery, it may become corroded by acid
fumes from the battery. It is a black cylinder about 2 1/2" long
by 1" diameter with a black/lt green wire.You'll find it up next to
the starter solenoid where the wire goes into the wiring harness
4.) All the sensors have a common separate ground. This
includes the TPS, ACT, EGE, BAP, & VSS sensors.
5.) The O2 sensor heaters have their own ground (HEGO ground)
coming from the computer. This is different and separate from
the O2 sensor ground. It is in the fuel injector wiring harness and
comes out under the throttle body. It gets connected to a
manifold or head bolt.
6.) The TFI module has 2 grounds: one for the foil shield around
the wires and another for the module itself. The TFI module
ground terminates inside the computer.
7.) The computer takes the shield ground for the TFI module and
runs it from pin 20 to the chassis near the computer.
8.) The computer's main power ground (the one that comes from
the battery ground wire) uses pins 40 & 60 for all the things it
controls internally.
See http://www.fluke.com/application_notes/automotive/circuit.asp?AGID=1&SID=103#volt
for help troubleshooting voltage drops across grounds
Extra grounds are like the reserve parachute for a sky diver.
If the main one fails, there is always your reserve.
The best plan is to have all the grounds meet at one central spot
and connect together there. That eliminates any voltage drops
from grounds connected at different places. A voltage drop
between the computer ground and the alternator power ground will effectively
reduce the voltage available to the computer by the amount of the drop.
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that makes sense!
hey thanks guys! i was tightening everything up on my car yesterday and noticed this problem today...i tightnened the tranny bolts so the ground makes total sense because the voltage is irregularly low with my new alternator...i probably knocked something loose in the process...ill check it later. Thanks again!
hey thanks guys! i was tightening everything up on my car yesterday and noticed this problem today...i tightnened the tranny bolts so the ground makes total sense because the voltage is irregularly low with my new alternator...i probably knocked something loose in the process...ill check it later. Thanks again!
I have a 3g alternator with 200amp output and have noticed that when I have the lights on at night the temp guage goes up a little and goes right down when the lights are off - the car is not overheating - new rebuild, new coolant, new waterpump, new 3 core radiator, 3.8 Taurus fan, etc.... I have installed another ground and have cleaned all the others, new battery, new battery cables, etc... It still does it. All I can do is just let keep doing it cause I know it is running fine. Let me know what fixes yours so I can try something else
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