620 CHG light is on. (very dim)

[ADavis_620]

I have a 77' 620 Datsun. recently driving down the road at night for the first time and notice the chg light was on but very dim. i checked my fuses and they seem to be all okay. Battery terminals don't have any corrosion and there clean. my next thought was alternator / regulator??? I'm new to working on vehicles so i'm just learning.any help or ideas would be greatly appreciated. Thanks.

[DanielC]

Check the voltage at the battery with a good accurate volt meter.  If between 13.5 to 14.5 it is OK.

 

The charge light is turned on and off not by a "normal" way.  When you turn the key on, engine off, the key applies battery voltage to one side of the charge light, and it is grounded by the alternator.  When the engine starts, battery voltage is still applied to the light, but alternator voltage is applied to the "ground" side of the light.   The two voltages are slightly different, so the light can glow very dimly.

[ADavis_620]

Okay thanks. i'll test them and see what happens.  B)

[ADavis_620]

I did the volt meter test and battery is good but my regulator was apparently bad. from what i saw the regulator is separate from the alternator unlike new model vehicles. O'riellys auto parts told me 60$ not including shipping and tax. so im looking at 70-75$ for new regulator. is that too much? Also what could this lead too if i dont replace soon and keep driving? Thanks for the help DanielC. 

[DanielC]

What is the voltage at the battery, engine running 1500 to 2000 RPM?   Before you condemn the voltage regulator, make sure all the wiring between the alternator, and the voltage regulator is good.  There should be a wire from the alternator frame, to the negative battery cable, and a wire from the alternator frame to the voltage regulator mount.  These connections should be clean.

 

I have had Datsun 521 trucks since the 1970's.  Not once, have I had a problem with the voltage regulator.  I would suggest you get a voltage regulator from a junkyard 620, before you get one from a chain auto parts store.  If not that consider possibly going to an internally regulated alternator from a newer Datsun.  Another option is to see if you can get a Nissan voltage regulator.  Yes, it will cost more than one from a chain auto parts store, but the quality of Nissan parts is way above that of generic stuff.  

 

The wiring on your 620 may be different than what I described.  My description is for a 521

[wayno]

I hate this problem, I dealt with it for years, at first the light was very dim, it was that way for a very long time, so I finally bought a voltage regulator and installed it and there was no change on start up, it was still on just a little till it went very bright after about 10 seconds after starting it, the regulator smoked itself, so I put the old one back in and nothing changed, it stayed on, bright yellow, so I drove it down to the auto parts store and they tested it, it was charging fine even with the light on.

I drove it that way for about a year until it would not start without a push one day, the battery was almost dead, when it actually quit charging, I could not tell because the light had been on for a year, I had the alt tested and it was fine, so I put another regulator in it, and it changed nothing, the light was still on, so I converted over to a internally regulated alternator and have not had any issues since except for a loose wire(the main one) on the back of the alternator.

When I made the change to the internally regulated alternator, I bypassed all the stock wiring except for the dash light wire, I figured there was something wrong with the stock wiring, keep in mind that I have a lot of problems with starters in this truck also, I have an aftermarket gear reduction starter waiting to go in the truck when the stock type starter finally pisses me off for the last time.

 

 

EDIT

 

After thinking about it for a while, I had issues with the internally regulated alternator also after a year or so, you see I used little jumper wires to bypass the regulator at first with the stock wiring, then I bypassed the stock wiring and that cured my issues.

[ADavis_620]

Very weird I haven't replaced anything yet but my chg light hasn't been on. Not sure what's going on.

[dr.feltersnatch]

Also pull the regulator off and make sure there isnt corrosion and rust blocking a good ground.

[ADavis_620]

So everything seems to be clean. I went got a voltage regulator from orielly's for about 55$. I haven't installed yet.. but as i was driving home from school i turned on my lights and as i speed up the lights get brighter and when i slow down or shift the lights dim. On and off dimming.... not sure if this is because of the chg light..?? any ideas?? or should i just install and see what happens?

[datzenmike]

The charge amperage varies with RPM. Revved up produces full charge.. unfortunately only about 36 amps. Sudden loads such as signals will cause drops in the charge and slight dimming of the other lights.  Idle with heater, head lights and turn signals is very noticeable. It's normal and only changed by a higher output alternator.

[ADavis_620]

So in the future if i decide to get a higher output alternator. what do you suggest?

 

The charge amperage varies with RPM. Revved up produces full charge.. unfortunately only about 36 amps. Sudden loads such as signals will cause drops in the charge and slight dimming of the other lights.  Idle with heater, head lights and turn signals is very noticeable. It's normal and only changed by a higher output alternator.

[datzenmike]

Try SEARCH for 620 alternator swap. There's several here I think. The 620 uses a small alternator and most car (Datsun) ones don't clear the idler arm below it. A 50 amp would do, 90 would always be better.

[banzai510(hainz)]

buy this

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

 

this will tell you some thing is going bad before you kill it.

 

get a volt reading at idle and at 1500 with a load on it say heater on. if a weak voltage then alt is most likly going out.

 

autozone sells the solid state volt regs and are cheap or car quest. The Mchanical USA made ones they want alot of money and break.

[ADavis_620]

buy this

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

 

this will tell you some thing is going bad before you kill it.

 

get a volt reading at idle and at 1500 with a load on it say heater on. if a weak voltage then alt is most likly going out.

 

autozone sells the solid state volt regs and are cheap or car quest. The Mchanical USA made ones they want alot of money and break.

Thanks for the link. should come in handy. yeah i went to oriellys again and had them test everything again. the first time it was regulator and now its the battery. battery is only 1 year old. i think they don't know what there talking about.

[ADavis_620]

The charge amperage varies with RPM. Revved up produces full charge.. unfortunately only about 36 amps. Sudden loads such as signals will cause drops in the charge and slight dimming of the other lights.  Idle with heater, head lights and turn signals is very noticeable. It's normal and only changed by a higher output alternator.

I was curious and decided to disconnect the radio/stereo system and now everything so far works perfect. why?

[datzenmike]

36 amps is 432 watts of power.... max!!! You probably need about 5-10 amps to power the coil and gauges when running so subtract 60-100 watts from that. Say 350 watts available to run your sound system... not much is it????

[ADavis_620]

buy this

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

 

this will tell you some thing is going bad before you kill it.

 

get a volt reading at idle and at 1500 with a load on it say heater on. if a weak voltage then alt is most likly going out.

 

autozone sells the solid state volt regs and are cheap or car quest. The Mchanical USA made ones they want alot of money and break.

Bought that battery monitor and everything is perfect as long as i don't have the lights and radio on at the same time.. haha. So I need a higher amp alternator or just get a Amp.