Low voltage until revved (1 Viewer)

[pumbaatx]

I am dealing with an issue where the voltage after starting is low. I can drive around normally and the ammeter remains low, under the halfway mark on the gauge (guessing around 9-11V). Once I rev the engine above 3k RPM, the voltage jumps back up to normal levels (guessing 14.4V or so). If I turn on different electrical devices (AC, radio, wipers, lights, etc), the reading drops a bit as expected but remains in normal range.

I noticed this problem after having the vehicle serviced, however they hadn't touched anything electrical and suggested it may just be the alternator going out coincidentally. I didn't really do any further troubleshooting myself and popped the alternator off to have it rebuilt. The alternator shop said everything, including the voltage regulator, looked good and just replaced the brushes. I inquired if that should fix the low voltage problem and they believed it would, however the problem has persisted after I reinstalled it.

I suspected a few things since: ammeter gauge going out in the cabin, bad fusible link, bad voltage regulator.

I have tested these things with my new multimeter:

• My fusible link shows 0.2 Ohm through each path (good connection)
• With the engine off
  • Battery reads 12.5V
• With the engine on before exciting/revving:
  • Battery reads 12.5V
  • Alternator reads 12.5V
• After revving the engine to ~3k RPM and not having driven anywhere
  • Battery reads 13.7V
  • Alternator reads 13.7V

At this point, with my limited knowledge, my guess is the voltage regulator is going bad and the shop missed it even though I asked specifically. 13.7V still seems a bit lower than the 14.4V number I see a lot of places as being normal, but I wonder if that's just because at this point I have only tested in my garage without driving around. Is there a way to confirm the voltage regulator is the issue before I order a replacement? Is that a straightforward thing to swap on the OEM alternator? Is there anything else I need to test?

 

[HemiAlex]

I like to idle my 2F a little higher for two reasons. Charging and cooling.

I run mine at 800 warm, ac off and 900 warm ac on.

This gets the alternator to charge a little easier off idle and the fan stays locked more at idle. It’s very noticeable with the FJ80 3FE fan clutch. It takes 10 mins of sitting in 90+ degree temps to make the coolant temps start to rise like this.

 

[OSS]

Battery voltage should instantly jump up right after starting the engine even at 750 RPM.
It’s good to have a spare voltage regulator handy anyway so it’s not a waste to buy one now to see if that’s the culprit. But generally, the purpose of a VR is to prevent over voltage during charging. It’s conceivable a dying VR could prevent proper charging at low RPM.

 

[pumbaatx]

Alright, here is what I found in the FSM. Seems that it could be a few things, so I’ll check these soon.

 

[pumbaatx]

Alright, the green plug on the back of the alternator has no power and the engine fuse in the cabin is blown. Any reason to not just put another fuse in and see if it holds? What causes that one to blow?How does adding load cause the alternator to be able to charge?

 

[pumbaatx]

Also, the large circuit breaker labeled POWER is also missing. Wtf? Seems like I probably need that, no? It’s been running for 3 years without it unless it got swiped.

 

[Spike Strip]

There's nothing in that lower spot on USA spec FJ60s. (actually there was a fuse puller in the square hole).

Diesels use that spot for another breaker.

 

[Seth S]

The battery light in the dash needs to come on with the key and needs to shut off when the engine starts. If the battery light is not coming on then the alternator is not getting a 12v signal and it won’t excite at low rpm’s. The alternator will self excite at about 3k rpm which you are seeing. That 12v provided to the back of the alternator helps create the magnetic field in the windings which is what is needed for charging. The battery dash light is part of that circuit. Once the alternator starts charging the battery light loses its ground and turns off.

 

[Spike Strip]

There's a 'Charge Lamp Relay' (in the above diagram it's called 'Discharge Warning Light Relay' that's under the passenger kick panel. They sometimes get dirty/corroded so if you remove it and remove the cover and spritz with some PLASTIC SAFE electronic cleaner and clean the spade contacts on the male and female side, that can help.

Don't bother trying to find a new one. Loooooong NLA and used ones are stupid expensive. There may be a substitute out there but I haven't found it. Maybe somebody with a knowledge of how this things work can fab a workable substitute.

 

[pumbaatx]

Well, what is a charge lamp relay supposed to look like? I can’t see anywhere where I visibly think I see a short, I’m also not getting continuity between posts 1 & 2 or 1 & 4 like the FSM states I should. Are these rebuildable with solder or am I SOL?

 

[OSS]

Here’s a used one-

Charge Lamp Relay 91-92 [27790-13010] - $55.00 : CruiserParts, The best place for Land Cruiser Parts!

CruiserParts Charge Lamp Relay 91-92 [27790-13010] - Used alternator warning light relay in good working condition.

shop.cruiserparts.net

 

[pumbaatx]

Here’s a used one-

Charge Lamp Relay 91-92 [27790-13010] - $55.00 : CruiserParts, The best place for Land Cruiser Parts!

CruiserParts Charge Lamp Relay 91-92 [27790-13010] - Used alternator warning light relay in good working condition.

shop.cruiserparts.net

The 80 series relays work for the 60?

 

[OSS]

Just go by the part number. No two Toyota parts have the same part number.
That charge lamp relay was used in several different Toyota models. Camry etc.

Supposedly there’s a new one available in Thailand for a whopping $171+ shipping

27790-13010 - Relay Assy, Charge Lamp, Toyota OEM | Megazip.net

27790-13010 - Relay Assy, Charge Lamp, Toyota. New spare parts Toyota from Japan with easy payment system and door-to-door delivery.

www.megazip.net

 

[george_tlc]

In the charge relay pictures you can see a diode (the black cylinder with a band). It's possible the diode is dead (open circuit). Basically the charge relay is just a relay with a built in series diode on the coil.

You could apply 12V to test that it 'clicks'. Do note that with the diode, it will only click if you have the polarity correct on the applied 12V. The outside pin further from the diode side should have +12V applied and the other outside pin that has the diode PCB copper trace would have 0V applied. The relay should then click. You can also test just the relay coil by applying the +12V as above and the 0V to the non-band side of the diode - that will apply the 12V only to the coil, the relay should click.

If the above isn't clear, I can draw some arrows on the relay picture.

cheers,
george.

 

[pumbaatx]

Ok the new one came in the mail today. Anything I should do to test the system to make sure I don’t pop the new one by installing it?

Trying to decipher anything else related with the wiring diagram. There’s a ground on one pin of the relay, the dash light, the alternator, the ignition, and the ENGINE, CHARGE, and GAUGE fuses.

 

[ToyotaMatt]

I am dealing with an issue where the voltage after starting is low. I can drive around normally and the ammeter remains low, under the halfway mark on the gauge (guessing around 9-11V). Once I rev the engine above 3k RPM, the voltage jumps back up to normal levels (guessing 14.4V or so). If I turn on different electrical devices (AC, radio, wipers, lights, etc), the reading drops a bit as expected but remains in normal range.

I noticed this problem after having the vehicle serviced, however they hadn't touched anything electrical and suggested it may just be the alternator going out coincidentally. I didn't really do any further troubleshooting myself and popped the alternator off to have it rebuilt. The alternator shop said everything, including the voltage regulator, looked good and just replaced the brushes. I inquired if that should fix the low voltage problem and they believed it would, however the problem has persisted after I reinstalled it.

I suspected a few things since: ammeter gauge going out in the cabin, bad fusible link, bad voltage regulator.

I have tested these things with my new multimeter:

• My fusible link shows 0.2 Ohm through each path (good connection)
• With the engine off
  • Battery reads 12.5V
• With the engine on before exciting/revving:
  • Battery reads 12.5V
  • Alternator reads 12.5V
• After revving the engine to ~3k RPM and not having driven anywhere
  • Battery reads 13.7V
  • Alternator reads 13.7V

At this point, with my limited knowledge, my guess is the voltage regulator is going bad and the shop missed it even though I asked specifically. 13.7V still seems a bit lower than the 14.4V number I see a lot of places as being normal, but I wonder if that's just because at this point I have only tested in my garage without driving around. Is there a way to confirm the voltage regulator is the issue before I order a replacement? Is that a straightforward thing to swap on the OEM alternator? Is there anything else I need to test?

i offer NOS FJ60 genuine NipponDenso voltage regulators

- they come with ALL new mounting hardware including the 3 NOS tiny 4mm screws under the regulator service cover


-

NOS OEM TOYOTA Genuine NipponDenso Voltage Regulator 27700-38100 FJ60 FJ40 FJ55 1978-1987 2F - VintageTEqParts.com

NOS OEM TOYOTA Voltage Regulator GENUINE NipponDenso JAPAN Made 27700-38100 - OLD Superseded / Interchange Part #'s 27700-28030 , 27700-41050, 27700-45021...

vintageteqparts.com

 

[pumbaatx]

i offer NOS FJ60 genuine NipponDenso voltage regulators

- they come with ALL new mounting hardware including the 3 NOS tiny 4mm screws under the regulator service cover


-

NOS OEM TOYOTA Genuine NipponDenso Voltage Regulator 27700-38100 FJ60 FJ40 FJ55 1978-1987 2F - VintageTEqParts.com

NOS OEM TOYOTA Voltage Regulator GENUINE NipponDenso JAPAN Made 27700-38100 - OLD Superseded / Interchange Part #'s 27700-28030 , 27700-41050, 27700-45021...

vintageteqparts.com

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I’m still likely going to pick one of yours up as backup after I get this resolved, Matt.

 

[Seth S]

I don’t think it would be a big deal to rewrite the alternator to work like other vehicles. Basically the circuit is 12v through a fuse through the dash light to the back of the alternator. When the alternator starts charging the circuit loses its ground and the light turns off.