Voltage Drop During Long Drive?

[GodziRRa]

Hi guys!

I have been experiencing some battery voltage drop when driving for around an hour. I would get a reading of 11.9 V from my HKS turbo timer (triple gauge battery voltmeter haven't checked it though ). This will also cause my Hicas light to flicker. The Hicas is a bit sensitive on voltage drops right? But when the car has just been started it's just fine having 13 + volts. Is this a sign of my alternator going out? Car is GT-R BNR32 by the way.

Hope you guys can help me out.

[t_revz]

might be an early warning sign the brushes are out of length or are jamming up and not moving down as they wear. other than that it must be heat causing something i guess. once the voltage drops different RPM doesnt make it change back up??

[UWAM]

Got a multimeter? Check the battery itself. If the wires from the turbo timer are getting too hot, it would lower the reading.

[GodziRRa]

Got a multimeter? Check the battery itself. If the wires from the turbo timer are getting too hot, it would lower the reading.

Guys thanks for the reply.

Anyways I do have a volt meter. I measured the battery when the car is off, and measured it again when the car is started. The values were 12.5 and 13.6 respectively. But I did not have a chance to measure it when the car is all warmed up and when it began to show 11.90 reading. I notice that when this happens my Hicas light starts to flicker during high rpm and when I put on my headlights high beam. So I confirm that these Hicas is indeed sensitive on voltage.

By the way, you guys mentioned heat. These babies really put up much heat under the hood. Maybe a wire in a very hot area...

Edited November 9, 2010 by GodziRRa

[GodziRRa]

I have a test of the battery and alternator again using a voltmeter. Before I start the car the battery was reading 12.5V. When I started it, initially it was around 13.30 - 13.50, that's the alternator output right. But after the engine was warm w/ the electrical stuff running like headlights, a/c, radio.. the voltage will be as low as 12.90 especially on high beam.

[t_revz]

maybe the hicas is draining power also. maybe pull the fuse for a couple days and see if it drops again

[GodziRRa]

maybe the hicas is draining power also. maybe pull the fuse for a couple days and see if it drops again

Is that the "Engine Control" fuse? I also feel the Hicas is actually telling me that my what... ummm 91' alternator has some symptoms of giving up already. Coz I notice on the road that every time all accessories are on, high beam also... the Hicas light comes flickering. Then when I try to unload a bit, the Hicas flickering light stops.

[GTsauRus]

Is that the "Engine Control" fuse? I also feel the Hicas is actually telling me that my what... ummm 91' alternator has some symptoms of giving up already. Coz I notice on the road that every time all accessories are on, high beam also... the Hicas light comes flickering. Then when I try to unload a bit, the Hicas flickering light stops.

hi i had similar problems with my gtr the problem is if the voltage to the hicas computer in the boot drops too low it resets believing the power has gone off and back on the real way to prove this is check for the error codes flashing and there will be no errors because the computer believes it was a restart and not an error. firstly i followed all wiring then unplug and cleaned all conectors that lead to the ignition switch from the engine bay fuse box then the same for all wiring to the back of the car where the hicas computer is, this fixed the problem for 12 months then it returned.

1 Next i ran an 8g cable from the battery to the boot to a fused distro block and connected to the fuel pump relay to give it 14.4v instead of 10.5v this improves fuel pump performance and unloads the circuit that also supplies the hicas computer [all via the ignition switch and other fuses]

2 Next find the cable splice near the alternator for the regulator sense wire, disconnect it and run a wire to the positive battery terminal to bypass voltage drop between the the battery and the splice this makes the voltage at the battery 14.4 instead of 13.4, this is required if you use a superior calcium battery that will not charge to full capacity unless the battery terminal voltage is 14.4v

Get a calcium battery its worth the extra dollars.

3 years later no hicas hiccups ever.

230kw atw and no longer leaning out on the dyno. [fuel pump voltage]

[GodziRRa]

hi i had similar problems with my gtr the problem is if the voltage to the hicas computer in the boot drops too low it resets believing the power has gone off and back on the real way to prove this is check for the error codes flashing and there will be no errors because the computer believes it was a restart and not an error. firstly i followed all wiring then unplug and cleaned all conectors that lead to the ignition switch from the engine bay fuse box then the same for all wiring to the back of the car where the hicas computer is, this fixed the problem for 12 months then it returned.

1 Next i ran an 8g cable from the battery to the boot to a fused distro block and connected to the fuel pump relay to give it 14.4v instead of 10.5v this improves fuel pump performance and unloads the circuit that also supplies the hicas computer [all via the ignition switch and other fuses]

2 Next find the cable splice near the alternator for the regulator sense wire, disconnect it and run a wire to the positive battery terminal to bypass voltage drop between the the battery and the splice this makes the voltage at the battery 14.4 instead of 13.4, this is required if you use a superior calcium battery that will not charge to full capacity unless the battery terminal voltage is 14.4v

Get a calcium battery its worth the extra dollars.

3 years later no hicas hiccups ever.

230kw atw and no longer leaning out on the dyno. [fuel pump voltage]

Wow nice work. Seems you are into electronics. Anyways, I ran a consult w/ the car and you're right there ain't no error code. It's just that when the engine running the alternator seems to give weak voltage output, and I believe does not fully charges my battery as well (w/c is a 4 month old optima yellow). Battery voltage around 12.48 engine off, alternator voltage is 13.5 initially then drops as low as 12.9 when warm. So your GT-R before does not have a weak alternator?

Edited November 12, 2010 by GodziRRa

[royb31]

Check and clean all your earths. bad earths do weird stuff. check alt 13.7v with no load then turn all the light etc to load up the alt (check at 2000 rpm) to check regulator. get it all hot and check it all again if the alt is still putting out 13v at the term on the alt but the voltage is low at the bat( check at both spots) you have a bad connection or a bad earth due to high current draw and heat.(hotter stuff gets the more resistance stuff has).has the bat been relocated??? are the cables big enough If it is a long cable run???

[GodziRRa]

Check and clean all your earths. bad earths do weird stuff. check alt 13.7v with no load then turn all the light etc to load up the alt (check at 2000 rpm) to check regulator. get it all hot and check it all again if the alt is still putting out 13v at the term on the alt but the voltage is low at the bat( check at both spots) you have a bad connection or a bad earth due to high current draw and heat.(hotter stuff gets the more resistance stuff has).has the bat been relocated??? are the cables big enough If it is a long cable run???

Now I must know where all the earth ground is for the GT-R. The battery has not been relocated, I think the cables are just fine. The problem just got a bit worse in the past few weeks and I haven't done anything. Initially I suspect alternator. No parasitic key off load by the way, already test it.

[GTsauRus]

Now I must know where all the earth ground is for the GT-R. The battery has not been relocated, I think the cables are just fine. The problem just got a bit worse in the past few weeks and I haven't done anything. Initially I suspect alternator. No parasitic key off load by the way, already test it.

some r32 gtr earth locations