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I'm not sure about diodes in the dash.
These cars have issues with grounds due to age. Have you gone over the various grounding points and cleaned the contacts? If there's more resistance on one of the grounds you could get a high powered component pulling power through a low power circuit which can have unexpected results.
Early summer I installed the IceShark battery and headlight kit. Followed the instructions and did a thorough job of cleaning all grounds and use dielectric grease. Hard to imagine an issue with the grounds. I need to retrace the steps though. The thing with the drop on the ground side is it fluctuates between 0 to over 0.2. I don't understand the fluctuation, and doing some reading I'm not sure it's enough of an issue to cause the charging problem.
I've been talking to another lister and followed his advise by tapping a wire with resistor on it into the blue sense wire from the battery. Alternator and anti-lock lights go out and voltage at idle increases to 12.36 without seeming to drop further, but not higher either. Increasing idle bumps volts up to 13.90, but as soon as idle returns to normal, volts drop down to 12.36 again. So there is still a problem, just don't no where yet?
There are several key points to be made here:
1. The alternator shop should perform a load test to show the alternator make design Amps, at rated volts ~14, and rated RPM (at the alternator). If all three of these conditions are met, the alternator is functioning properly. Just testing for voltage output will NOT provide the info to determine the alt is good, you can have failed rectifier diodes, or issues with the rotor and still make volts, but not design amps.
2. The Sense wire is connected to the battery with a 10 amp fuse. This is the battery reference voltage for charging (see 4 below)
3. The supervisory ignition power, is provided through the idiot light and a diode. Both of these devices; the light and diode, offer voltage drop, not much, on the order of ~.5-1 VDC. This power should not be wired hot, as the regulator is powered continuously, and can fail. I have not looked at the 951 idiot lamp circuit, but I suspect this can be used. May need diode.
4. The proper charging voltage for a battery will vary with the battery temperature. Most cars built in the last 20 years vary the charging voltage based on outside temperature. (you can Google this). This is why most batteries seem to fail in the summer, as the are overcharged. Summer float 13.6 volts, winter float 14.1 volts. Cars that do not charge on outside temp, always go to 14.1-4 volts.
5. The load side issues are a consideration. These alternators are not rated for more than say 25-40 amp continuous output, or they will overheat and fail. So alt temperature, and amps load are issues to be aware of. I have not looked at the alt spec sheet, it will list rated continuous load at working temperatures.
6. Be aware the volt reading in the dash, is affected by the number of devices operating; headlights, A/C,... Measure the reference volts at the battery with a known good voltmeter. Rest voltage for a good battery is 12.6-7 volts, where rest is no activity for 30-60 minutes, at 70 deg F.
7. You can, on the car, test the alt for load. Typical engine RPM is 2,000, to spin alt at rated rpm. Then use either battery load tester or switch on all available loads in the car, and look for 13.6 (70 deg F) at the battery, on a good voltmeter. Recognize an alternator test at rated amps of say 125a, is very short term, a few seconds.
Last edited by Alan 91 C2; 12-30-2015 at 01:43 PM.
Nice post. The OP will hopefully do this as posted. If the OP doesn't have a load test machine - AutoZone, Batteries Plus, etc. will do this for free. The shop that did the work can tell if the alt is working properly in short order.
Originally Posted by Alan 91 C2
There are several key points to be made here:
1. The alternator shop should perform a load test to show the alternator make design Amps, at rated volts ~14, and rated RPM (at the alternator). If all three of these conditions are met, the alternator is functioning properly. Just testing for voltage output will NOT provide the info to determine the alt is good, you can have failed rectifier diodes, or issues with the rotor and still make volts, but not design amps.
2. The Sense wire is connected to the battery with a 10 amp fuse. This is the battery reference voltage for charging (see 4 below)
3. The supervisory ignition power, is provided through the idiot light and a diode. Both of these devices; the light and diode, offer voltage drop, not much, on the order of ~.5-1 VDC. This power should not be wired hot, as the regulator is powered continuously, and can fail. I have not looked at the 951 idiot lamp circuit, but I suspect this can be used. May need diode.
4. The proper charging voltage for a battery will vary with the battery temperature. Most cars built in the last 20 years vary the charging voltage based on outside temperature. (you can Google this). This is why most batteries seem to fail in the summer, as the are overcharged. Summer float 13.6 volts, winter float 14.1 volts. Cars that do not charge on outside temp, always go to 14.1-4 volts.
5. The load side issues are a consideration. These alternators are not rated for more than say 25-40 amp continuous output, or they will overheat and fail. So alt temperature, and amps load are issues to be aware of. I have not looked at the alt spec sheet, it will list rated continuous load at working temperatures.
6. Be aware the volt reading in the dash, is affected by the number of devices operating; headlights, A/C,... Measure the reference volts at the battery with a known good voltmeter. Rest voltage for a good battery is 12.6-7 volts, where rest is no activity for 30-60 minutes, at 70 deg F.
7. You can, on the car, test the alt for load. Typical engine RPM is 2,000, to spin alt at rated rpm. Then use either battery load tester or switch on all available loads in the car, and look for 13.6 (70 deg F) at the battery, on a good voltmeter. Recognize an alternator test at rated amps of say 125a, is very short term, a few seconds.
I've had a Nissan alternator in my 951 for eight years with zero issues. I'm running two subs, high output lights, etc. Without this mod, my turbo, downpipe, and intake would never fit. We modified the factory bracket - if it ever fails, trust I'll be using one of the newer brackets. Modifying the factory bracket with perfect alignment isn't fun - took many hours of grinding, spacers, etc. to get it to exact alignment so the belt would wear evenly.
I've had a Nissan alternator in my 951 for eight years with zero issues. I'm running two subs, high output lights, etc. Without this mod, my turbo, downpipe, and intake would never fit. We modified the factory bracket - if it ever fails, trust I'll be using one of the newer brackets. Modifying the factory bracket with perfect alignment isn't fun - took many hours of grinding, spacers, etc. to get it to exact alignment so the belt would wear evenly.
+1 on the effort needed to fit it!
I wonder how many different alternators are sold as "Nissan Quest" alternators? I know mine needed more grinding and fitting than most reported. There are a ton of Nissans around, so there are probably a number of after market units, all of which fit the Quest, but present their own unique challenges when going in a 944. You can imagine that the quality of some are way better than others, which may explain why some have better luck than others?
I think it's likely remanufactured vs NEW. Your "additional" grinding and fitting is because your tolerance towards "fit" requires tenacity. You can get the belt to turn the alternator, likely for many miles being off center. You'd never settle for that!
Originally Posted by Tom M'Guinn
+1 on the effort needed to fit it!
I wonder how many different alternators are sold as "Nissan Quest" alternators? I know mine needed more grinding and fitting than most reported. There are a ton of Nissans around, so there are probably a number of after market units, all of which fit the Quest, but present their own unique challenges when going in a 944. You can imagine that the quality of some are way better than others, which may explain why some have better luck than others?
I think it's likely remanufactured vs NEW. Your "additional" grinding and fitting is because your tolerance towards "fit" requires tenacity. You can get the belt to turn the alternator, likely for many miles being off center. You'd never settle for that!
George, curious what you are referring to by 'new bracket'? I've had the EBay alternator for a year now and would love to get it on, but have been dreading all the cutting/grinding to come. I did check my EBay unit and it will need the massaging Tom had to do. I'd love to get a CEP bracket but have been unsuccessful to date. Is there another option?
I'm not aware of another option in addition to CEP...but likely out there. Broadfoot may have one - give them a call. If it's on the shelf, they'll ship quickly.
G
Originally Posted by mtnman82
George, curious what you are referring to by 'new bracket'? I've had the EBay alternator for a year now and would love to get it on, but have been dreading all the cutting/grinding to come. I did check my EBay unit and it will need the massaging Tom had to do. I'd love to get a CEP bracket but have been unsuccessful to date. Is there another option?
I searched and found this photo from when I built my engine. I thought I had some of it with belt installed and some of bracket prior to installing alternator. Notice the notch I decided to cut for clearance.
I did have an issue, the sense wire ended up burning up the track on the back of the instrument panel, it took me a while to find it but this was caused by a metal maf tube making contact with the alternator batter + lug. It grounded the circuit when I was not paying attention trying to get the MAF tube out of the way while doing some under hood cleanup. I have since cut the lug to be much shorter and used a much better fitting lug boot. I could see how this could happen if you were to get too much current on this circuit. I have also put a fuse in line on the sense wire, it is less than 5 amps, but I can't remember the exact. The cluster could be repaired with a jumper wire, but the track
de-laminated the entire length. I just bought a good used one from Lart.
Wow this thread is old post from an even older post.
That is my alternator in the pic on the OP and how I wired it a loooong time ago. I put probably 25k miles on the car since, up until I sold the engine. In fact I still have that alternator sitting on a shelf in case one of my N/A track car alts go out.
Here's is that exact same alternator today from the OP pic. Not a thing wrong with it.
From what I recall when I got this working, only the blue wire needed to be switched which it was. The jumper wire is the reference voltage and probably could use a diode so the alternator can see a difference voltage however the blue wire does need to be switched. I did have a battery go bad which this alternator flawlessly took over allowing the car to run after a jump. So for me it worked exactly as shown.
If I were to do this today I would probably pick an even smaller alternator and make a custom bracket from scratch but back then...it was a different time for me.
Hi thinking of installing a quest alternator due to bigger turbo fitment you mention grinding the case down ?does this alternator give more room or not ?
Hi thinking of installing a quest alternator due to bigger turbo fitment you mention grinding the case down ?does this alternator give more room or not ?
Welcome to rennlist! Yes, this alternator provides extra room for big turbochargers! See additional info in this thread:
There are several key points to be made here:
1. The alternator shop should perform a load test to show the alternator make design Amps, at rated volts ~14, and rated RPM (at the alternator). If all three of these conditions are met, the alternator is functioning properly. Just testing for voltage output will NOT provide the info to determine the alt is good, you can have failed rectifier diodes, or issues with the rotor and still make volts, but not design amps.
2. The Sense wire is connected to the battery with a 10 amp fuse. This is the battery reference voltage for charging (see 4 below)
3. The supervisory ignition power, is provided through the idiot light and a diode. Both of these devices; the light and diode, offer voltage drop, not much, on the order of ~.5-1 VDC. This power should not be wired hot, as the regulator is powered continuously, and can fail. I have not looked at the 951 idiot lamp circuit, but I suspect this can be used. May need diode.
4. The proper charging voltage for a battery will vary with the battery temperature. Most cars built in the last 20 years vary the charging voltage based on outside temperature. (you can Google this). This is why most batteries seem to fail in the summer, as the are overcharged. Summer float 13.6 volts, winter float 14.1 volts. Cars that do not charge on outside temp, always go to 14.1-4 volts.
5. The load side issues are a consideration. These alternators are not rated for more than say 25-40 amp continuous output, or they will overheat and fail. So alt temperature, and amps load are issues to be aware of. I have not looked at the alt spec sheet, it will list rated continuous load at working temperatures.
6. Be aware the volt reading in the dash, is affected by the number of devices operating; headlights, A/C,... Measure the reference volts at the battery with a known good voltmeter. Rest voltage for a good battery is 12.6-7 volts, where rest is no activity for 30-60 minutes, at 70 deg F.
7. You can, on the car, test the alt for load. Typical engine RPM is 2,000, to spin alt at rated rpm. Then use either battery load tester or switch on all available loads in the car, and look for 13.6 (70 deg F) at the battery, on a good voltmeter. Recognize an alternator test at rated amps of say 125a, is very short term, a few seconds.
Thanks Alan, Finally got the charging system working properly. Most likely it was a bad alternator. Even though it was tested four different times, the computerized test equipment could not seem to accurately pin point the problem.
During the different tests, a failed regulator was to blame twice, a broken rotor wire was discovered, following this on another test, it wouldn't make over 30 amps, albeit it was putting out proper amperage on prior tests after repairs were made.
Finally gave up and the shop ordered a new one. To be thorough, I also went ahead and replaced the charging system bulb and resistor on the circuit which may or may not have been contributing factors.
After pulling it four different times, I was overjoyed to see it making 13.8v with nice bright Ice-Shark headlights on! While the cluster was out, I refurbed the light tunnels using Rustoleum Mirror Finish paint with a black back coating and replaced the bulbs. With the electrics working well and the tunnels restored, it sure is nice to have a bright instrument panel and headlights!
12-30-2015, 12:44 AM
