Hitachi LR150 50A alternator

[Zoltan]

I got one of those cheap rebuilts... It was heavily leaking oil, so I have to replace the oil seal. I found this oil seal at my local bearing shop:





I wanted two, but the second one was a Spanish "model" with single lip only and the rubber was rather hard (probably an old stock).

[philip]

That alternator oil seal is my next project. From all the oil ... lately ... I cannot descern the lost oil is due to the vacuum pump seal or the ancient rubber oil hose connecting the vacuum pump back to the engine block.

Then again, the ONLY replacement in that alternator are the bushes I did 40k miles ago. It's High Mileage now for an alternator.

[ecomike]

Well now I have screwed the pooch. Fixed one problem on the wiring between my alternator and the battery and overloaded the alternator. Any chance there is a thermal overload current overload protection in the alternator or its built in voltage regulator?

I added an AC condenser fan about 18 months ago but today I increased the wire gauge from the alternator output to the battery because I noticed it was getting way too hot with everything turned on, head lights AC blower on max, plus the condenser fan, and the wire was about 8 ft long and only 10 gauge (remnants from the prior owners wiring the Nissan to the Jeep). So I added another 10 ga wire as a patch. It ran better, cooler, more voltage at the battery under full load, but then the voltage dropped off to about 12.5 V, so I guess I am screwed, and off to pull it and repair or swap it. I had it rebuilt locally about 16 months ago. I will post some data on it when I get back tonight.

[asavage]

Any chance there is a thermal overload current overload protection in the alternator or its built in voltage regulator?

No, and no.

Short the output and the diodes short. Don't short the output and the diodes crack. Either way, the diodes are the weak spot.

. . . but then the voltage dropped off to about 12.5 V, so I guess I am screwed . . .

This could still be a wiring issue. The alternator isn't self-exciting. If it doesn't get voltage via the Ign. circuit (via the warning lamp), it won't turn on.

(Click on image for larger)

[ecomike]

Nothing was shorted, all I did was increase the load carrying capacity of the wire that carries the charging current back to the battery, this was done by adding a second parallel 10 ga wire next to the existing, overloaded 10 ga wire. That got the battery voltage up a little higher than previously under a full appliance load, and no doubt finally pulled more current than the diodes could handle. Wishing I had added fuses now.

To the best of my knowledge mine has never had the Nissan resistor (unless it is in the alternator) or warning lamp wired into the starting circuit. Mine is a straight shot from the battery to the ignition switch then to the alternator, I think, but if I leave a load directly on the battery running on mine that by passes the ignition switch, and I turn off the ignition switch, then later turn on the ignition switch just to the run position, I find the alternator and VR still working. However, if I turn off all the electrical appliance loads the alternator (or voltage regulator) will shut off completely in just a few minutes. At that point the alternator will never turn back on until I kill the engine and restart the engine. I think there is some kind of a start up switch in the alternator that resets when it stops rotating and restarts when the rotation hits a critical speed at start up.

Mine has two separate hot + battery wires running directly to two separate posts on the alternator, no resistors, no ignition switch, etc. That is the way it was when I bought the beast 5 years ago, and so far I have had no real problems, at least none that I knew of.

So, now I am wondering what the resistor is for, and what its specs are?

So is it the diodes, or the voltage regulator that gets fried first? I guess you already answered that one.

While I am looking into the alternator repair or replacement, I am also looking into ways to drop the voltage and current draw of the two AC fans.
On the jeep the blower usually operates through a resistor that is cooled by air flow in the AC-Heat duct work mixer box area, but I had multiple wiring and AC blower switch problems through out that area, and I finally just bypassed it all with a direct connection to a 30 amp fused switch near the battery under the hood. It has worked fine for several years, but it seems that both fans and the head lights is just a few more amps than this alternator can handle. I think what was happening was that the battery - alternator system voltage was dropping just enough at night to keep the alternator just shy of overloading, which also explains the slightly dim head lights and dash lights in the summer when I use the AC at night. I thought I was solving the problem by adding the extra wire needed to carry the current to the battery, but you know how that story ended now. That is what happens when we get into too much of hurry.

The alternator invoice I have from 2006, Oct, says the part number was a 14615, which matches the part number of a 50 amp alternator that Advance Auto parts quoted me earlier tonight for the SD22 diesel. The printout that came with my receipt shows the rated output was 50 amps, Test results showed 68 amps max output at 5000 rpm, 40 amps at 1600 rpm, and turn on rpm as 1820 rpm. It also shows 14.9 V as the regulator set point, and finally the printed out report that came with the receipt shows lamp status on=> off and NO active lamp what ever that means?

I was looking in the FSM today and my copy shows the only SD22 diesel alternator to be a 60 amp, LR160-97B, but I am thinking you guys have been talking about 50 amp, LR150 alternators for the SD22??? and the alternator I seem to have and have been quoted says 50 amp rated, and tested at 68 amps, so I have missed something?

Looking at page EL-23 of the 82 Nissan/Datsun FSM I can not make heads or tails out the second wiring diagram, but I see the one you (Al) posted above at the top of the page.

[asavage]

The L terminal should be switched by the Ign. and should be current-limited by some means -- maybe a 20 ohm resistor in parallel with a 194 lamp?

Your installation would be an excellent candidate for an LR160 Maxima diesel alternator upgrade. See this post and this post for more info.

[ecomike]

So why does the 1982 FSM for the 720 pick up show that diesel SD22 only came with the LR160? See page EL-25.

Can you elaborate on what the 20 ohm resistor does in the run to pin L?
Any idea what wattage it needs to be?

I found a small wire that looks to be going to pin L that does not go directly to the battery. I have the three wires marked W on the wiring diagram that go from pin B directly to the battery, and what must be WL running L, but I don't know for sure where it comes from yet. I am guessing the ignition switch.

[asavage]

So why does the 1982 FSM for the 720 pick up show that diesel SD22 only came with the LR160? See page EL-25.

I've been operating on the assumption that it's a typo (the model No.).

Can you elaborate on what the 20 ohm resistor does in the run to pin L?

No. Well, since it's wired parallel to the idiot light, it's obvious that it provides more current to the voltage regulator when the key in ON, than the idiot light wattage would on its own.

Any idea what wattage it needs to be?

I've never measured it. I would start with a one watt, and if it doesn't smoke, it was large enough. Though I'm guessing a half-watt resistor would do.

I was hoping that someone else would find and measure that resistor, but nobody ever has.

I found a small wire that looks to be going to pin L that does not go directly to the battery. I have the three wires marked W on the wiring diagram that go from pin B directly to the battery, and what must be WL running L, but I don't know for sure where it comes from yet. I am guessing the ignition switch.

I hope that the L wire (color: WL) goes to your Charge (Alt) idiot light!

For those of you following along at home, I think the resistor is mounted to the left fenderwell. Oval connector, from memory.

[ecomike]

Don't think I have an alternator idiot light, If I do I ignored it since it's for idiots (LOL), I have a Jeep OEM voltage meter in the dash that is active and working.

I pulled the alternator today. No markings or part numbers on it at all, nada, zip, nothing on it anywhere. Looks to be the 50 amp, LR150. I am going to try a different local alternator shop tomorrow and let them rebuild it (if the quote is reasonable, otherwise I will try and source the parts from him), I would love to do it myself, but don't have the time this month, unless left with no other option. But this guy sounded like he knows what he is doing, and he was familiar with this alternator.

Also, I could not find an LR150 in stock in Houston anywhere.

I would love to have a complete drop in LR160 with the vacuum pump ready to go, but alas all I can do it seems is dream about that.

[ecomike]

I find it curious that there is a 15 amp fuse listed in front of that resistor. Makes me wonder if 1 watt is anywhere near large enough for that resistor.

Scott at the alternator shop told me that many newer vehicles have the resistor built into the light bulb itself. Makes me wonder if Nissan might not have already been doing that in 82.

He tells me he has a friend that builds custom alternators and starters in California.

I picked up a standard AC SCR dimmer/ceiling fan variable speed controller / switch today, 600 watt, that I plan to use for speed and power usage control of the AC condenser fan, it should help me drop the power load on the alternator some. Even though they are sold for AC, 120 volt devices, IIRC they also work on DC in DC out DC motor loads as I used one for DC battery charging research once.

I also bought an aftermarket bulb and capillary variable control thermal switch that I am going to use to cycle the AC condenser fan, as I probably only need it at idle, and for extended idling in heaving traffic.

Then I plan to try and repair the AC blower wiring with the stock load control / blower speed control resistors to get the power load back down on that AC/heat blower. Now that I have fixed the AC damper door problem (missing vacuum line that supplies vacuum to close the outside fresh air damper door for max AC) I don't need that blower on max speed all the time anymore, which was part of the reason for the earlier bypass.

[asavage]

I find it curious that there is a 15 amp fuse listed in front of that resistor. Makes me wonder if 1 watt is anywhere near large enough for that resistor.

That schematic is a fragment, specific to the charging circuit. Fuse 4 feeds a lot more than just the charge idiot lamp.

While it looks at first glance that the entire positive feed for the field coil (rotor) is via that fuse, the idiot lamp, and the resistor, that's only for startup, and you do not need much of a magnetic field to kick off an alternator. After startup, the alternator's diode trio (the three diodes to the left in the schematic, physically a lot smaller than the main diodes, because they don't have to do much) supply all the field coils' current. Which is why the idiot lamp goes out: 12v+ (nominal) on the Fuse 4 side of the lamp, 12v+ (nominal) on the "ground" side of the lamp: no current flow (or very little), no lamp light.

(Which is why some older rigs have a glowing idiot lamp when driving at night: with bad wiring, the alternator's voltage at the diode trio is higher than at the Ign. switch or fusebox.)

For that parallel resistor, 1W should be plenty. I do wonder at the actual resistance value though.

Scott at the alternator shop told me that many newer vehicles have the resistor built into the light bulb itself.

Scott must know something I don't. The lamp is a resistor, and the normal resistance of the lamp allows (on most of these older alternators) enough current to kick off the alternator. GM & Ford didn't use a parallel resistor, and neither does the LR160 version of this alternator. I'd bet it's there to solve some intermittant, one-percent problem that most of us will never see. If the idiot lamp works, I bet the LR150 starts up just fine without the extra resistor.

New alternators are even wierder than that. Many VRs are now actually in the ECM, and it's now common for the VR to change charge value based on other conditions: when you step on the brake, the alternator bumps up to 15v, to do poor-man's regenerative braking (take advantage of wasted kinetic energy to accelerate the charge rate). Cold start: charge to lower value until the engine is idling smoothly and the load can be handled more gracefully (when the engine is warmed up). Like that. The modern VRs are now compensating for the phase variance internally (most alternators are three-phase).

But I wonder how yours is wired. I suppose that having 12v+ to the L terminal (without lamp or resistor) might work OK if you don't care about an idiot lamp and if the regulator doesn't fry, but it's going to mean pretty heavy current draw with key ON engine OFF (maybe two to five amps, which is relatively heavy compared to things like dome lights), and the wiring to the L terminal is not designed to carry enough current to handle the capacity of Fuse 4. Summary: it might be considered a fire hazard.

I'd use the lamp or a suitable replacement resistor. I doubt that the actual resistor value is all that important.

Makes me wonder if Nissan might not have already been doing that in 82.

No, I've seen what I think may be the resistor on the left fenderwell of a couple of early 720 diesels. I just haven't taken the time to confirm it.

I picked up a standard AC SCR dimmer/ceiling fan variable speed controller / switch today, 600 watt, that I plan to use for speed and power usage control of the AC condenser fan, it should help me drop the power load on the alternator some. Even though they are sold for AC, 120 volt devices, IIRC they also work on DC in DC out DC motor loads as I used one for DC battery charging research once.

I want to see you use an SCR with DC input to do phase-chopping output to 12v fans! I really do!

Save yourself some grief: get a big dropping resistor from any 80's Taurus at a JY, wire it in series with your fan(s), mount a switch near your dash, and wire the switch to bypass (short out) the big resistor. Efficient? No, you'll have heat dissipation to deal with, the resistor will be dropping 2-4 volts but a lot of current. But simple and reliable. Two fan speeds is enough.

If you run multiple fans, do away with that idea and have them come on in stages. You can either use dual thermostat triggers, or if you must get complex, use a thermister and a microcontroller to toggle individual relays for each fan.

The possibilities are plentiful. But SCRs like to switch at phase zero-crossing, and you don't have zero-crossing with DC. I'm not an EE though, I don't even play one at work.

I also bought an aftermarket bulb and capillary variable control thermal switch that I am going to use to cycle the AC condenser fan, as I probably only need it at idle, and for extended idling in heaving traffic.

I no longer have the schematic for the system I installed in my '83 G30, in 1994, but you will need to use an A/C high-side pressure switch (cheap, at any large A/C repair center) to toggle your fans to get idle fan control. That's what I did, it worked a charm. I had custom-engraved LED panel indicators (the lenses were engraved, very cool) made to tell me when the fans were on because of the A/C pressure switch, or if they were one because of thermostat demand. I added a third engraved indicator that read "A/C cycling switch" to let me know when the compressor was running too. I was pretty proud of that.

[ecomike]

I want to see you use an SCR with DC input to do phase-chopping output to 12v fans! I really do!

I am not an EE either, sometimes wish I was, but I get pretty deep into parts of it at times. You lost me with the phase chopping comment. Are you suggesting I need something like a diode and capacitor on the output side of the SCR to stabilize the load?

I don't recall for sure, but I seem to recall these being used for variable speed control on DC powered hand drills. Guess from the sound of your comment I need to look further into it. Perhaps I can introduce a smaller 9 volt battery on the output side for stability, if it is needed.

I do know it will drop the output DC voltage (from an input DC voltage) with out the heat losses of a resistor! We used them for variable voltage output from a 12 volt battery charger input and used it for charging a DC prototype research battery we were (and are again) developing. I thought I recalled using it on a DC motor as well, that was back in 1981.

[asavage]

I do know it will drop the output DC voltage (from an input DC voltage) . . .

You know something I don't.

We used them for variable voltage output from a 12 volt battery charger input . . .

As the input to a battery charger, AC input, yes. I've used a phase-chopper (SCR) on the input of a marine power supply to create a variable-rate battery charger, and on an unsophisticated (old) battery charger with a linear power supply (a transformer, not a Switch Mode Power Supply), an SCR works OK.

I'm unaware of SCR designs using DC as input. Doesn't mean they don't exist, but even IGBTs are easier to work with than SCRs for DC, or so I've read.

Anyway, if you get it to work, I'm interested in the circuit. Though I still think the two-speed fan control that most other mfgrs use (Subaru, Volvo, VW, Ford) is adequate for almost any situation I can envision. And you'll still need a high-side pressure switch or transducer to toggle the fans on at low forward velocities to get enough condenser airflow. I don't think your capillary bulb setup will react fast enough to the condenser temp changes to prevent loss (via the relief valve) of working fluid, and excessive high-side pressure is murder on the compressor. The cheap pressure switch, screwed onto the gauge port, worked perfectly for me. I think I paid under $20 for it from "Mac's Radiator" in SE Portland, Ore. in 1994 (they do a lot of A/C work, and are also a Vintage Air dealer). It was a non-adjustable switch, ON at 200 PSI or similar.

[ecomike]

Well I have a gauge set up so I can watch (test) the high side pressure and try different bulb locations on the condenser, and different ON temperature settings at those locations as this one goes from 32 F to 248 F. Good thermal contact and outer insulation around the bulb to condenser contact area should help. I am planning to set the thermal on temperature pretty low. If it does not work out I will try it your way. I think I already have a high pressure switch, but it is a HP cut out that shuts off the AC clutch, that is a recent add on. In fact I think it is a dual HP/Low Pressure cut out switch, one switch that cuts out at high or low pressure.

[asavage]

In fact I think it is a dual HP/Low Pressure cut out switch, one switch that cuts out at high or low pressure.

That's an OEM-style part. You'll want an aftermarket part whose HP threshold is much lower than the OEM part.