620 IR alternator testing: ON or OFF truck.

[datsundash]

1977 620 with sr20det swap. My charge light is slightly on. Left my hid's on for about 10 minutes and truck would not start. Battery is relocated under my bed for visual and space purposes. Removed battery and 2 amp trickle charged it. After charged battery was tested and found to be good. Next step is to verify connections on alternator, all connections solid and clean. Now we get to the alternator testing part. Simply put the alternator is a bitch to remove with the radiator, charge pipes, and everything else in the way. Therefore, I would rather not remove it. Because my battery is under my bed, its hard to get the tester hooked up to do a system load test. My question is, Can I use the positive output stud on the back of the alternator and an earth ground to test my alternator? The reason why I ask this is because of how the IR alternator is wired up. The output of the alternator runs through the engine harness and back out through the fusible link to charge the battery. One time I tried to jump start another vehicle and I burned my fusible link. I have made a spare fusible link out of an atc fuse and could replace the link with it incase it did decide to pop (to save my 12$ fusible link).

 

Maybe I need to run another hot wire from the stud on my alternator to my battery?

[ggzilla]

Just take it down to Autozone and they'll test it on the vehicle.

 

Charge light on a little bit is not necessarily a problem -- see your 620 service manual for details.

Battery dying after 10 minutes on lights is -- battery is "OK", but not "great".

 

Or, to test the reserve capacity, now that it is "fully" charged, leave your lights on for 15 minutes and see if it goes flat again.

[datsunaholic]

What are you trying to test for? A simple voltmeter attached anywhere in the system will tell you if there is output. You hook it up, read the voltage with the ignition on but engine off. Should be between 12.0 - 12.3, depending on how soon the battery was charged. When you start the engine, the voltage should go to 14.0 +/- 0.5V. It won't tell you how many amps it puts out, but to do that you need a verifiable load bank, which really can't be done in-vehicle.

[izzo]

You know, if you have a multimeter you can test it in the car also.

 

Battery should be around 12v with motor off... Fire it up, should be around 14.4. if its still around 12 with the motor running, rev it up and see if it changes. sometimes you have to hit a higher rpm for the alternator to kick in, sometimes they are worn out and need to be a little higher rpm to work.

[datsundash]

YES YES YES YES YES I built and wired this thing by myself. All I want to know is if I can have the alternator tested while on the truck without burning something down. The load tester will have to be hooked up to my alternator and not to my battery, unlike a normal alternator charge system test. I have verified voltage with a meter and with consult through my laptop and ecu. I NEED TO HAVE A LOAD TEST DONE. I also understand that the charge light being barely lit is normally not a problem. However mine HAS NEVER BEEN LIT BEFORE, and suddenly it lights up and Im having charging issues, does that strike anyone else as odd?

[datsunaholic]

Usually that kind of load test IS the battery, so hooking up that kind of load tester to the alternator will overload the wiring. Most load tests simulate a starting load on the battery. If you think your alternator wiring can handle 200A...

 

All you need is the voltmeter test. Start engine. If it reads 14.2 volts or thereabouts, that verifies the alternator is charging, at least at that low load. Then turn on the headlights and heater fan and wipers and brake lights. At idle, it'll drop like a rock, as low as 11V. But rev the engine- anything over 2000RPM should be enough for the alternator, and it should get the voltage up at least to 13.5V. If it doesn't, the alternator can't handle the load.

 

Here's an alternate though. Use the starter's battery terminal. It can take the load. Unless you installed a remote Starter solenoid, then you need to use the always hot side of that.

[banzai510(hainz)]

What Datsunaholic said above is a simple no cost ck.

 

 

Maybe I need to run another hot wire from the stud on my alternator to my battery?

 

Why? is it there or not?

[datsundash]

there is no wire running from the back of my alternator to my battery, there never was. Just the thick white/red wire coming out of the alternator, and into my engine harness.

[ggzilla]

Do NOT put a load on the small alternator output wire.

 

All I want to know is if I can have the alternator tested while on the truck without burning something down.

YES.

* You can do a voltage test with a voltmeter (13.5-15.0 volts @ 1200 rpm is good, but only if the battery is fully charged)

* You can do a load test. But that needs battery cable connection.

[datsunaholic]

Hm- so where is the battery connected then? The "Thick white/red wire" coming from the engine harness actually went straight to the battery via the fusible link. Obviously it connects into the wiring somewhere, since the thing runs, right? Is that thick red wire still "hot" all the time? It should be, else the alternator has no path back to the battery.

[datsundash]

the battery is conected tot he starter, from there I have a 4 awg wire running into a distrobution block (fused) one side of the block I have my radio, fuel pump, can am box, fan etc wire to and the other side has the fusible link for the chassis harness hooked to it. not only do I have the fusible link but also a 60 amp atc fuse. at idle with no load im getting 13.25 volts. just the battery reads 13.16 volts. At idle with everything electrical on Im getting between 9.5 and 12.5 volts. My alternator is SHOT!!! hooray!!!

[banzai510(hainz)]

Just the thick white/red wire coming out of the alternator, and into my engine harness.

 

Thats it!!!!!!!!!!!!Thats the wire.

 

if battery is in there and you take that red/wht wire and touch metal it will spark. Meaning it HOOKED up to the BATTERY!!!!!

 

 

now this is a 77 so I assume this was a external volt reg truck and you conneverting the wiring at the external volt reg and used the 2 jumpers to use the IR alternator.

Or was this a IR truck to begin with.

 

 

I would ck for voltage at the stater lug and ground.

[datsunaholic]

the battery is conected tot he starter, from there I have a 4 awg wire running into a distrobution block (fused) one side of the block I have my radio, fuel pump, can am box, fan etc wire to and the other side has the fusible link for the chassis harness hooked to it. not only do I have the fusible link but also a 60 amp atc fuse. at idle with no load im getting 13.25 volts. just the battery reads 13.16 volts. At idle with everything electrical on Im getting between 9.5 and 12.5 volts. My alternator is SHOT!!! hooray!!!

 

 

Sounds like the alternator is worn- usually that's sign the brushes are worn down to where they "float". But those symptoms are also indicative of too much wiring length or too many connectors, all of which cause voltage drops. But if that voltage is the reading at the alternator, it's probably worn. The .09 volt drop from alternator to battery is more than I'd like to see, but with that much distance probably not concerning.

[banzai510(hainz)]

Just make sure the batt cables are good or the ends.I hate those piece together ends.

 

I was loosing voltage with a crack battery lug.

 

run this in the cig lighter so you can monitor it. These work good. dont drain the battery either.

You can drive with it and learn what not to load down esp at idle.

http://equus.com/Product/3721/Battery-Monitor

these are worth only 10$ I think

 

when i had my 510 my 35amper would drop below 12 with the heater and H4 lights and wiper ON. The heater blower motor on my car draws the most power. Might need to be cleaned.

[ggzilla]

Yes Hainz, that's why alternator output wire goes through Fusible Link in stock form. To prevent fires.

[datsundash]

The positive battery cable is jl audio true 4 awg 99.99999% pure copper with new 4 awg copper ends crimped and then soldered and heat shrunk for corrosion protection. The negative is 4 AWG copper also crimped and soldered. I'm running a 78-dlg side post duralast gold with 1,000 cranking amps at 32* F. Every connection is soldered and heat shrunk. This isnt a 35 year old beat up truck anymore. I have completely been through everything. The alternator just decided to take a shit on me the other day.

 

Hainz, why would I go buy a voltage meter for my cig lighter when I can view voltage and all the other sensors on my laptop through consult (ecu talk).

 

I was just curious about load testing the alternator while on the truck. Tomorrow its coming out along with my radiator to get the pinholes fixed. Should be back together in a few days.

 

GGZILLA, you are exactly correct, this is how the charge gets from the alt to the battery. Not only do I have a new oem fuse-able link I also have a 60 amp atc fuse in my distribution block.

 

I will try to get some pics of everything tomorrow to ease some of your guys minds. Maybe I cant explain it the best, but trust me all of my circuitry is fully protected better than oem, and all connections are solid and new. Thanks for the help.

[datsundash]

Here is the distribution block I use to power any non factory components on my rig. Everything is fused and run straight from the battery. The HID's and the fan are also run off relays.

 

http://www.jlaudio.com/car-audio-connection-systems-power-connections-distribution-blocks

[DanielC]

This is how to test an IR alternator on the vehicle.

Connect the frame of the alternator to the negative post of the battery. Do not depend on mounting bolts to ground the alternator.

Connect the positive output on the alternator to the positive post of the battery. Optional, put a cheap auto amp meter, with a higher scale than the alternator output.

Before starting the engine, use a test light from the positive post of the battery to the "L" terminal. The light should light up.

Start the engine. The test light should go out. if you put the amp meter in series with the positive lead, it should show you the amps the alternator is putting out. The battery voltage should be 13.5 to 14.5.

 

The S terminal on the alternator is a voltage sense connection. Since you have relocated the battery, you might try using a relay, switched on by ignition, to connect this terminal to the battery, so the internal regulator actually knows what the battery voltage is. Because of the length of the wires, and the many connections you made, the alternator may not be getting a true voltage reading.

 

One additional note. Unless you have checked the voltage reading against an accurate calibrated source, you have no guarantee the numbers your computer or whatever you are using to read voltage is accurate.

[ggzilla]

If there is a 0.9v drop from ALT to BAT you have a wiring problem and should use bigger battery cables so the drop is less than 0.5v

 

The S terminal on the alternator is a voltage sense connection. Since you have relocated the battery, you might try using a relay, switched on by ignition, to connect this terminal to the battery, so the internal regulator actually knows what the battery voltage is.

Or do what Nissan did, connect it directly to the Fusible Link (unswitched). Since you have a big fat wire right at the Alt + terminal, just connect it there. Some think this will drain the battery but it won't if you are using Hitachi LR150 alternator (the large size 1978/1979 Datsun internally-regulated alternator).

[banzai510(hainz)]

Hainz, why would I go buy a voltage meter for my cig lighter when I can view voltage and all the other sensors on my laptop through consult ?????

 

cause this is 26$ which most datsun guys might. I say might be able to AFFORD.Plus its EZer to look at while driving.

 

But Lucky that computer did all that trouble shooting to find its just a bad alternator.

 

we all asusume the fusable link is in the system and the red white wire is hooked up to the output of the alternator.

[ggzilla]

Yes, the advantage of the in-car voltage gauge is that it is always available.

[datsundash]

Removed the alternator and tested it myself on the bench. The diodes/rectifier failed. I de soldered all the connections and took it all apart. found parts online for it but ended up ordering a whole brand new unit for 215$ YIKES!!!!

[ggzilla]

That's crazy. Rebuilt 620 IR alternator is $50 at local auto parts stores like Autozone

[datsunaholic]

That's crazy. Rebuilt alternators are $50 at local auto parts stores like Autozone

 

That only take 3-4 tries to get a working one...

[datsundash]

read my first post in this thread, this is an sr20, not your average 35 amper.