Failed Alternator Overvoltage.. Would it Damage any of the Electrical Systems

[cdndub]

I picked up a 1992 Q45 from a long time enthusiast earlier this year for an excellent price, I have never owned a vehicle with such a perfect maintenance record/history. Same owner from 66k km's to 310k km's with records of all the work he'd done.

The car ran well when I picked it up, however i quickly became a victim of failed valve cover sealant leaking oil into the plug galleys. I decided to change the plugs and after avidly reading through the forums here paid the money for a set of the OEM recommended ones along with several new hoses while everything was apart.

This teporairly fixed a misfire condition and hesitation below 2k rpm, and the car regained some of its lost power.

Sadly this problem keeps rearing its head and I've finally ordered a consult cable and software as I give up on being able to troubleshoot it without.

However now that i've rambled about the history of how I came to this point My actual question for all the experts here is around a failure that occured after doing the above fixes.

After suspecting the alternator was failing for a few weeks and checking it with a DVM <both at idle and at 3-4k> for both DC volts and AC volts the problem finally came to a head and it must have had failing diodes in the rectifier that only showed up after it had warmed up etc.

In the end it turned out the diodes completely failed, it wouldnt charge at idle and the car stalled out on my wife a few blocks from home, however when restarted it would charge but at 18-19volts at 2k rpm.

Enough overvoltage that it boiled and slightly melted the battery which probably further compounded the problem by dripping battery acid down onto the alternator.

I spent $350 on a Bosch Reman of an OEM Nissan alternator which appears to be good quality.

I also installed an Optima Red Top at the same time as I have long despised wet cell batteries for all the rust/damage they cause under the hood over time.

Charging system is now good, 12.8-13volts at 500rpm with the car running, 14volts as soon as it comes up over 650-800rpm

But the misfire has come back, I changed out the MAF, checked all the vacuum lines, injectors etc and with the MAF change it now runs much smoother. I also pulled the codes and had a code 12 and 13 show up

I've already gone through all the electrical connectors under the hood once with DeoxIT D100 and then DeoxIT Sheild to clean and then preserve all the connections for the injectors, sensors etc.

Now that the cooler weather has come to roost the A/C display has suddenly started turning itself off once the car warms up I'm guessing there is a bad solder joint or failing capacitor etc inside that is now heat sensitive.

However that problem coupled with the overvoltage from the alternator I'm starting to wonder if it may have damaged the FCPU or fuel pump or things like the AC controls.

I'm wondering if anyone knows how well protected the electronics are in the Q from things like this.

I'm going to jumper the FCPU and check to see if i've just lost the low range and will T in a Fuel pressure gauge and check that as well, the pump is quiet and was replaced fairly recently according to the documents i've got from the previous owner. I think its now on its 3rd or 4th pump since it was new.

Sorry for the wordy/convoluted post just thought i'd fill in some of the background info.

Dave

[Q45tech]

If FPCU loses one of 3 control ranges there will be Zero current flowing when ecu commands that range. Car won't idle or cruide when warm without pushing on accelerator pedal more than normal.

Middle range will give poor acceleration unless pedal [TPS voltage] is WOT or >70%.

Why I have a 100% spare inventory of every electronic module just incase I miss a bad alternator but I've installed a warning light which activates at >15.0 volts................................http://www.rlocman.ru/shem/i/u...d.gif

[qship96]

If FPCU loses one of 3 control ranges there will be Zero current flowing when ecu commands that range. Car won't idle or cruide when warm without pushing on accelerator pedal more than normal.

Middle range will give poor acceleration unless pedal [TPS voltage] is WOT or >70%.

Why I have a 100% spare inventory of every electronic module just incase I miss a bad alternator but I've installed a warning light which activates at >15.0 volts................................http://www.rlocman.ru/shem/i/u...d.gif

I am shocked you didnt pull the clock and replace with a digital multi function LED readout gauge that toggles between volts, oil pressure, trans temp, and coolant temperature.

[maxnix]

I am shocked you didnt pull the clock and replace with a digital multi function LED readout gauge that toggles between volts, oil pressure, trans temp, and coolant temperature.

That's not a bad idea if it had automatic switch over on failure mode.

[Infinitiguy19]

I am sure you can put a single mulitifunction gauge, But then where you put the beautiful clock?

But seriously any multifuntion gauges out there?

[Jesda]

Dennis is insane, and awesome.

[cdndub]

I jumpered the fuel pump and it got louder, but the misfires and bucking/hesitation was still there.. oddly since the new MAF its moved the problem down lower closer to 1500rpm where as it would occur right around 2k previously.

You could hear the pump in the cabin when it was jumpered but not when its running off the FPCU, As soon as its not -20 outside i'll T in a fuel pressure gauge and swap out the fuel filter again to see if theres any measureable difference.

I know the pump is supposed to run quiet its almost silent at idle with the FPCU hooked up not so much when its jumpered.

Might be time for a new pump, Its probably been 40-50,000km's..

I'm still not sure why the Q45 pump is so flakey, i've owned many brands of and many models of vehicles over the years and even a VW Rabbit pump with a tank full of rust will somehow survive to 150k

Has anyone tried putting a different pump in the tank? I've got several Bosch Motorsports 044 Fuel pumps in stock, they'll deliver enough flow and pressure to fuel up to ~700hp and are about the same price as a new Q45 pump. They can be mounted vertically in tank as well as inline.

I love the car, its like a Tractor in the snow, and I'm determined to get to the bottom of these small annoyances.

Still not sure if anything was damaged by the alt overcharging for a short while.

Its funny, the Pioneer Stereo I installed has several "entertainment" displays.. one of which is a voltage gauge so its been left on that now for months.

[cdndub]

As for multifunction gauges, check out http://www.plxdevices.com I saw their whole product lineup at SEMA this year and was impressed enough to contact them about becoming a dealer.

They offer exactly what your talking about a multifunction gauge however its only OBD2 not OBD1 so only useful for people with 96 or newer Q's i guess. I just like OLED's for their readability in a car.

Dave

[cdndub]

I have a hunch that I'm chasing ghosts and probably do have a vacuum leak that has appeared as the temperatures dropped, when i had the intake off I changed some of the hoses but not all of them. Given the mileage the car is getting 20L/100k ~ 11-13mpg mixed city/hwy irrespective of driving style <granny vs lead foot> the new <different not brand new> MAF seems to have improved things slightly but not greatly.

Put 30Liters of 92 octane in last night after 170km's of driving..

I'll post up when I finally get to the bottom of the problem, though I do see owning a parts car <or two> in my future.

[maxnix]

How about KS and their sub-harness? EGR valve?

[cdndub]

Both Knock sensors were changed shortly before i purchased the car, subharness was in rough shape so i rebuilt it with new connectors and wire. KS's ohm out at 500k ohms each which seems within spec <checked in the engine bay and at the ECU side.

[qship96]

As for multifunction gauges, check out http://www.plxdevices.com I saw their whole product lineup at SEMA this year and was impressed enough to contact them about becoming a dealer.

They offer exactly what your talking about a multifunction gauge however its only OBD2 not OBD1 so only useful for people with 96 or newer Q's i guess. I just like OLED's for their readability in a car.

Dave

Thats the gauge I was talking about to replace the clock! I am pretty sure they do make the gauges for pre obd2, you just have to add a sensor for certain parameters you wish to monitor and display. Since alot of garden variety domestic sedans now come with little round analog clocks in their dashboards, the Q has lost some of its uniqueness for having one, so might as well swap it out for something more useful?

[Q451990]

ISadly this problem keeps rearing its head and I've finally ordered a consult cable and software as I give up on being able to troubleshoot it without.

I agree that this is your next step.

As far as the HVAC controller, it's a common issue - I wouldn't suspect that it's related to your alternator failure.

If your issue with your spark plugs swimming in oil was severe enough, you might want to try replacing the boots on the bottom of the coil packs. I have heard of them being damaged or corroded in these situations.

Good luck!

Heath

[cdndub]

I was just out in the Q in traffic for a few hours and am starting to think that maybe the whole issue is transmission related, as in the torque converter lockup not functioning as it should and disengaging properly.

the hesitation/bucking can be felt more in the drivetrain than as a mild misfire its also been unseasonably cold here in Vancouver the last few days and the Transmission has a B&M external cooler with no heat exchange via the radiator. The fluid is still nice and red, doesnt smell burned but its probably time to change it anyways so i'll order up the gaskets etc and filter and figure out what the best ATF, synth vs non etc.

Fluid level looks fine on the dispstick as well and I dont leave puddles behind anywhere.

the bucking does feel a lot like if a torque converter was locking and unlocking in rapid succession and causing the motor to misfire as it wouldnt be expecting the load.

I did run AT-CHECK the other day and it came back with an OK which of course tells me nothing. Hopefully a consult cable, and some new fluid is all she wants for christmas.

[Q451990]

Your extremely cold temperatures coupled with the cooler may be the issue. Although the B&M plate design is supposed to allow the fluid to warm up by bypassing the entire cooler core - it still may not be enough. I always envisioned a set of gate valves for a far north Q that would allow the owner to switch back over to the OEM radiator "heater" in the winter months.

If I'm not mistaken the A/T has an internal temp. sensor that is used to lock out TC lockup until it reaches normal operating temperature. I'm not sure if it could hunt if the temperature was right on the edge - I know a late 80's Maxima we owned was notorious for it.

Heath

[cdndub]

Sadly I wish I could blame REALLY cold temperatures but uneasonably cold here in Vancouver is -12C at night and -8C during the day with a -10C windchill.. thats about 10-20F which could be on the cool side for the B&M, It may also just be the fluid since I dont know what type of ATF was used its possible it was selected for its higher temperature properties and is too thick at cooler temps.

IT would in theory be possible to hook up a pair of high pressure/temperature rated solenoid controlled T Valves and a temperature sensor that could blend between the cooler and the integrated rad cooler. Just have to find the right valve

[Q451990]

I agree with your temperature ideas... My thinking was off due to the F vs C temperature scales. I have run the Q in those temperatures here (rarely) with the B&M cooler with no adverse transmission behavior.

I like your solenoid idea, but the simplicity of a gate valve that would be flipped in fall and then again in spring eliminates a lot of "$10 part killed my $4K transmission" fears.

Heath

[maxnix]

Not plumbing the the ATF in series with the OEM heat exchangers will slow ATF heat up on short trips.

Other than that, I doubt there is much about which to be concerned.