Reman Denso alternator problem (1 Viewer)

[valdi2012]

Wife's daily driver, 2000 Land Cruiser 223K. Original alternator died 3 weeks ago. Outside of a gentle "power steering-like hummm" there were NO other red flags (dim forward lights, dash, hard start), then the battery light illuminated on the way back from work. After a general inspection, nothing seemed out of order but I did purchase a reman Denso alt. since it seemed like the culprit. Next day as she was driving home, everything shut down. Had it towed home and began the process of replacing the original alt.

I moved the power steering pump out of the way for more space and noticed it was wet, like a leak, but the PS fluid level hasn't moved although I haven't been keeping an eye on it. Reservoir levels between max/min both hot and cold. Also have a slight valve cover gasket leak around the PS pump/alt.

Completed the alt. swap and everything worked great until 2 days ago. Got the frantic call that it died again without any warning, not even a dash battery light. Had it towed home AGAIN and was able to see that the battery light was illuminated. Trickle charged the battery overnight and started the engine today to inspect. Same "power steering-like hummm" that gets worse especially when I turn the brights on.

Mutlimeter readouts at the battery: OFF-12.72, IDLE-14.27, 1800K RPM-14.34

The installed reman alt. looks clean but could PS fluid and/or oil leak ruin the alt. in 3 weeks or less? Bad reman? I have another reman alt. on the way. Other ideas welcome, thank you in advance.

 

[AlpineAccess]

Wife's daily driver, 2000 Land Cruiser 223K. Original alternator died 3 weeks ago. Outside of a gentle "power steering-like hummm" there were NO other red flags (dim forward lights, dash, hard start), then the battery light illuminated on the way back from work. After a general inspection, nothing seemed out of order but I did purchase a reman Denso alt. since it seemed like the culprit. Next day as she was driving home, everything shut down. Had it towed home and began the process of replacing the original alt.

I moved the power steering pump out of the way for more space and noticed it was wet, like a leak, but the PS fluid level hasn't moved although I haven't been keeping an eye on it. Reservoir levels between max/min both hot and cold. Also have a slight valve cover gasket leak around the PS pump/alt.

Completed the alt. swap and everything worked great until 2 days ago. Got the frantic call that it died again without any warning, not even a dash battery light. Had it towed home AGAIN and was able to see that the battery light was illuminated. Trickle charged the battery overnight and started the engine today to inspect. Same "power steering-like hummm" that gets worse especially when I turn the brights on.

Mutlimeter readouts at the battery: OFF-12.72, IDLE-14.27, 1800K RPM-14.34

The installed reman alt. looks clean but could PS fluid and/or oil leak ruin the alt. in 3 weeks or less? Bad reman? I have another reman alt. on the way. Other ideas welcome, thank you in advance.

After the alternator runs at idle for awhile, does the voltage step down to low/mid 13's? If not, the alternator could be overcharging due to bad connection/ground that is signaling the regulator to keep it at peak charging. If that is the case and its been running at that 14-14.5v range I would check your battery as overcharging can cause swelling and premature failure. I found this was the case twice on non-toyota vehicles when a shop replaced a ground and alternator wire on them without making sure the wire gauge was correct. The bad connection and or smaller gauge wire is essentially a resistor, tricking the alternator into running at peak output thinking the battery is undercharged.

It's amazing how good the OEM alternators are; remans are pretty good but I'd put more stock in the reman being bad than a little power steering fluid killing it. But that's speculative, you'll only know when you pull it and see if its all gummed up with ATF!

 

[valdi2012]

Ill check tomorrow to see if it steps down. Electrical trouble shooting is new to me, had to buy a multimeter! My cruiser has been virtually maintenance free outside of PM, tires, exhaust and starter. I do have a 98 Volvo V70 T5 240K that keeps me busy wrenchin.

The battery was dead once I got it back home, trickle charged yesterday, so I don't think its being over charged. The ground your referencing...is that on the starter or battery? I didnt mess with OEM harnesses, 1 clip in plug and 1 bolt on stud wire on my alternator. From what I've researched, "around 14 volts" was acceptable?

 

[kwon-offroad]

If the voltage stays in that range then it’s too high for an OE spec alternator. And if you’re running a standard wet battery you’re overcharging it and slowly killing it.

“Around 14v” is only acceptable if you’re using a booster *and* running the correct battery to take that voltage (ie AGM).

 

[suprarx7nut]

If the voltage stays in that range then it’s too high for an OE spec alternator. And if you’re running a standard wet battery you’re overcharging it and slowly killing it.

“Around 14v” is only acceptable if you’re using a booster *and* running the correct battery to take that voltage (ie AGM).

I was about to agree, but I pulled out the manual. Apparently with no load, 14.8V is acceptable on an 06LX.

 

[kwon-offroad]

Interesting. Never seen that part of the spec in the FSM. Probably covering both charge and float range.
OP's battery doesn't seem to be the problem with the standing voltage, but a flooded lead acid should not exceed a 13.8V float charge or it'll get too hot and sulfate. There's something funky with the regulator or wiring that it's giving that idle voltage 100% of the time.

 

[valdi2012]

thank you kwon-offroad and suprarx7nut​

 

[AlpineAccess]

You should see a charging spike after starting; its not uncommon for me to see values above 14v as the system tops up the battery. It then drops to 13.1-13.7 based on the system's draw on the battery. Make sure to measure voltage from the positive battery terminal and a nearby ground (not the negative battery terminal) - You want to read the total system voltage and not the voltage where the battery is siphoning off power to top up.

If you have a bad ground or connection (particularly at the alternator harness or output cable) you will get an overcharging situation. Running over 14v for most than say 1-3 minutes is going to be either a bad battery (requiring a lot of charging) or bad signal and your alt is overcharging a good battery.

I'm not a guru on this stuff but have trouble shot a few charging systems and that is the gist of what I commonly find. Our voltage regulator is in the ECM from my research so if its the ECM its spendy bit - I like to verify everything else that costs less first.

 

[valdi2012]

Tested voltage at the battery this morning, readings below.

Cold OFF: 12.67
IDLE: 14.75 (all electronics off)
IDLE: 12.72 (all on: brights/heat/fan HI/seat heat/rear defog/mirror/radio)
2K RPM: 12.60 *slow climb up in numbers (all on: brights/heat/fan HI/seat heat/rear defog/mirror/radio)
IDLE: 12.94 *operating temp (all electronics off)
Warm OFF: 12.86

*slow climb up...noticed numbers climbing 12.55, 12.56, 12.57 etc. intervals about every 2 seconds.

 

[jerryb]

the regulator is @14.2v LX and LC

If I was to see and verify with two different meters a 14.3 or higher I'd remove the alt.

Running over 14v for most than say 1-3 minutes is going to be either a bad battery (requiring a lot of charging) or bad signal and your alt is overcharging a good battery. I agree

I'd be nervous above 14.3 probably more like pissed off, really you probably need a new battery and at least an inspection under the cover on the alt. VOltage regulators are pretty cheap.

 

[valdi2012]

You should see a charging spike after starting; its not uncommon for me to see values above 14v as the system tops up the battery. It then drops to 13.1-13.7 based on the system's draw on the battery. Make sure to measure voltage from the positive battery terminal and a nearby ground (not the negative battery terminal) - You want to read the total system voltage and not the voltage where the battery is siphoning off power to top up.

If you have a bad ground or connection (particularly at the alternator harness or output cable) you will get an overcharging situation. Running over 14v for most than say 1-3 minutes is going to be either a bad battery (requiring a lot of charging) or bad signal and your alt is overcharging a good battery.

I'm not a guru on this stuff but have trouble shot a few charging systems and that is the gist of what I commonly find. Our voltage regulator is in the ECM from my research so if its the ECM its spendy bit - I like to verify everything else that costs less first.

Damn...my latest numbers were on the battery +/-. Ill check again using the ground.

 

[valdi2012]

+ battery terminal/ - nearby ground numbers below...

Warm OFF: 12.73
IDLE: 14.24 (all electronics off)
IDLE: 12.03 *slowly drops (all on: brights/heat/fan HI/seat heat/rear defog/mirror/radio)
2K RPM: 11.70 (all on: brights/heat/fan HI/seat heat/rear defog/mirror/radio)
2K RPM: 12.19 (all electronics off)
IDLE: 12.10 (normal running lights and radio)
Warm OFF: 12.49

20 months/11K miles on Interstate 24F 700CCA

 

[valdi2012]

Pulled the replacement reman alternator this afternoon and noticed a white paste-like substance on both the alt/harness. My original alt. has very little white paste-like inside and I don't recall seeing any on the harness clip after removal/inspection and prior to installing the replacement reman alt.

 

[valdi2012]

I was thinking this was lithium grease but very little was present upon removal of original alt. and none on the harness connection. Could it be PS fluid and/or oil leaking through?

 

[nissanh]

13.4 V to 14.4 V is acceptable. All my Toy's run in that zone.

With a load, such as AC and headlights, you should still see around 13.2 V at idle (anything above 12.6 is charging). Clean the connector and try. If you still have the OEm alternator, try to swap the brush kit in the denso reman into your OEm unit and try. Always remove battery terminal before removing the alternator.

 

[valdi2012]

Just unpacked the "new" reman alt. and noticed the female alt. connector for the male harness wire is filled with the white paste...didn't see that the first round...ugh. Dielectric grease for those who know nothing about automotive electrical issues like me.

Going to install the "new" reman tomorrow.

 

[Coop661]

I've been having similar struggles. Replaced the stock alternator with a Denso reman on my 01 LX with 175k. Now it wants to idle around 500rpms which I guess is too low for the alternator to charge. If I bump the throttle up to 700 it starts charging but isn't as strong as my stock alternator which usually ran in the mid 14s under load. But now reading this post it looks like maybe my stock alternator was overcharging? I replaced my positive battery cable connection and today I'm going to do the negative cable connection as I found after cleaning it became loose. Hope you get yours straightened out!

 

[OwnerCS]

I don't remember white grease on mine. Though I would have used some clear CRC or Permatex dielectric grease. I use dielectric grease on all engine compartment and weather-facing electrical plugs. Seems to help keep away electrical gremlins.

 

[Coop661]

My old alternator had white grease in the connector and plug and the reman I got also had a spot or two of white grease in the plug

 

[2001LC]

Some points that come to mind reading this:

When testing voltage with multimeter. Test voltage from multiple spots. Directly on battery post, away from posts on clamps and from a ground further downstream. All should read the same. If voltage drops from point to point, something is inhibiting current. Most common: oxidation on battery post.

A battery under charged or one that sit long periods without a full charge, will sulfat. Which then, battery will not accept a full charge. Often times if caught early, the condition can be reversed. By using high AMPs repeatedly to charging on the bench. A good battery will show 13V or more, just after a full charge on the bench. When I see them under still 13V after I've "high AMP" charged, I replace the battery.

Battery care:
Clean battery & clamps with baking soda & water mix. Neutralizing and removing all battery acid.
Disconnect negative battery post first and re-attach last.
Clean battery post and clamps, removing all gray oxidation unit nice and silver Old school, coat post & clamps with white lithium grease, to ward off oxidation.
Do not over tighten battery clamps. Doing so stretches clamps to point their useless. Just snug them until clamp will not spin on post, with mild hand force applied "trying" to rotate.

Toyota Denso reman is best.
Denso reman second best.

I've not noticed alternators coming with female connection coated with white lithium grease. I'll look closer at next one. But if I see one, I'd be very suspect it's a returned alternator. Every so often, even form Toyota. I'll get a part that someone returned, which may be their old used one in stuck in the new box. If was new returned electrical part, they may have shorted it.

I've also noticed more alternators failing in rigs without #1 undershild (skid). Likely due to excessive water, dirt, satls, etc blow into alternator.

Other connection(s) also must be inspected.

Wiring too needs inspecting, as with age they may become past oxidized internal beyond useful life.

Here's new OEM positive clamps & main wire block. What they should look like.