amp guage problem? (1 Viewer)

[MiniPigg]

I really hate to do this but my wife isnt giving me any time to stay on the computer as she wants to go out for dinner.... here is whats going on.

1977 FJ55. Headlamps dim but brighten up with rpm. Amp guage stays at midline, until lamps are turned on and then it drops. The amp guage also fluctuates with the turn signals on. So I figure maybe the voltage regulator might be either bad or going bad or needs a cleaning and adjustment. Pull it and according to the FSM it fails one of the tests. So today I get my school loan in and decide to buy a brand new battery, alternator, cables, belts, and voltage regulator from scampa autoparts. The only item I bought at napa was the voltage regulator. They are the only people in town that had it in stock. So I clean the ground cable connection at the engine... and install all my new parts. I turn the truck on and it the lamps arent dim at idle. I drive it around town and they stay bright. But when I turn them on with the new voltage regulator the needle drops all the way down to the negative and when I use the turn signals in conjunction the needle goes back and forth. What in the hell am I doing wrong? Does this new regulator need some sort of adjustment for the amp guage? Well got to run.... This is my only vehicle... please lend some help as I need to get this fixed.

thanks and help is more then appreciated... will be back on later tonight when we get back.

thanks again

 

[Pin_Head]

This is pretty normal behavior, with the exception that the amp meter shouldn't continuously read negative (discharge) with the headlights on. Check the alternator output: Momentarily run a jumper wire from the battery + post to the field (F) post on the alternator and check if the amp meter reads zero or positive. If so the alternator is OK. If not, the brushes are probably shot on the alternator.

 

[MiniPigg]

but its a brand new alternator... just installed it today. with the old voltage regulator it would do the same thing... but only at midline.... as soon as i switched to the brand new voltage regulator it went all the way down to the negative line and stayed there with the headlamps on... I went ahead and just installed two brand new grounding straps with no effect.

Tomorrow I will go ahead and bring it in for a free charging diagnosis. One positive is I dont notice any fluctuation in the brightness of the headlamps at either idle or when you bring up the rpm. They seem to remain constant which makes me think the charging system is fine... Which it also did with the old voltage regulator. I replaced the alternator, battery, cables, etc... and then tried it with out replacing the voltage regulator... then put in the new one to see what the differences might be... only reason I replaced it to begin with was because it tested bad according to the FSM using impedance readings. Only one reading was bad. All the others were ok. I even cleaned the contact points and tried it again with the same readings. Think I will test that new one too.. if they read the same I think I will just put the old one back on and try to get my money back from scampa auto parts.

 

[Pin_Head]

but its a brand new alternator... just installed it today. with the old voltage regulator it would do the same thing... but only at midline.... as soon as i switched to the brand new voltage regulator it went all the way down to the negative line and stayed there with the headlamps on... I went ahead and just installed two brand new grounding straps with no effect.

.

I missed the new alternator part, so I wouldn't suspect that it is part of the problem. I guess that I don't understand what the problem is even after reading all this. So what is the problem again? The more detailed the better.

Anyway, if the amp meter pegs to the left and stays there when you turn the headlightlights on, it is indicating a major discharge. Is the wiring stock? If the alternator connects directly to the battery or battery side of the amp meter (not stock wiring), this could explain this behavior.

Other than that, what you describe sounds pretty normal if I am getting it.

 

[MiniPigg]

hmm... ok.. then maybe its normal.. i just dont remember it ever happening on any of my other cruisers. i mean a little needle deflection was detected... but this is making a considerable movement. On this truck with the factory VR (voltage regulator) once you turn the headlamps on the factory amp guage (ammeter) needle deflects to (-) about a 1/3 of the scale. Then with the headlamps on and the turn signals going it goes down further and then back to where the needle rests with the headlamps on. Now with this new VR it goes all the way down to the negative and the needle bounces down and back again with the turn signals on.

I tested both VR's... according to the book the readings are as follows:


Terminals:

IG and F = Armature released 0 ohms
Armature pressed down 11 ohms

IG and E = Arm released 100 ohms
Arm pressed Infinity

F and E = Arm released 100 ohms
Arm pressed 0 ohms

Mine reads pretty close to all these readings. Except with it is supposed to read Infinity.. it reads the same as the 11 ohms. The brand spankin new one from napa (their highest quality line which the salesman was so vocal on how it exceeds factory specs...hahaha) read 69 ohms when toyota sez 100ohms and instead of 11 ohms it reads 7 ohms. I cant test IG and E armature pressed because I would have to open the napa VR... im going to try and get my money back... just tell them it wouldnt fit.... hopefully they will take it back with out much of an arguement.

So am I worried over nothing? Otherwise Im going to keep troubleshooting.

 

[mr_manny]

to test your alternator
================
If you have access to a volt/multi meter, perform the following:
1. test battery voltage
2. have your wife start the truck and increase the rpms to approx. 2K , now re-test battery voltage

your voltage in step 1 should be 12 Volts (or above).
I believe there are some figures in the shop manual, but you should see 13.7-14.5 Volts in step 3.

 

[Pin_Head]

What I am not clear on is whether the amp meter STAYS negative when you have the lights on or if it just momentarily deflects and then goes back to the center.

If it stays negative, it isn't normal.

The issue is whether your battery is actually discharging or not

Drive it around for 30 minutes or so with the headlights on and then turn them off. Check the amp meter: If it has a large positive deflection for several minutes, then it indicates that your battery was discharging.

Does your alternator connect directly to the battery (or to the battery side of the amp meter)? That would explain it, but then the amp meter would never read to the right or charging direction.
Does the meter ever deflect to the passenger side or indicate that it is charging the battery?

 

[MiniPigg]

pin... I went ahead and replaced the VR with another one. Still does the same thing. What I mean when it goes into the negative is that it shows a serious load being applied to the charging system. The needle drops down and stays there the entire time the headlamps are on. The if I need to use my turn signals the needle will flucuate up and down with the timing of the flasher relay, and the head lamps go dim and then bright again in sync with the turn signals. So looks like I might need to work on my wiring some more. I have installed some extra grounding straps between the frame/engine/body and then from the battery to the alternator. Im going to go out and do some more work... let me know what you think.

 

[MiniPigg]

This is driving me nuts... ok I went and hooked the pig up to a tester. It showed a constant 2.5 amps no matter what rpm the engine was at. Pulled the brand new alternator and put it on the bench. Tested it 4 or 5 times and it tested good everytime. Soo.. back to the pig.

I pulled that premium highest quality voltage regulator that napa sold me. You should have heard the guy talking his product up.... but I had no choice because there were only two in town... The dealership had a new one for 115 dollars and napa had this one for 30 bucks.... I went the 30 dollar route..
Anyway I pull the VR and put my old Vr back in... place it on th diagnostic tester and the higher the rpm went up the higher the amps... went up to 54 amps. The Ammeter inside the pig now goes up and down with the rpm. At idle it sits midline.

 

[GetsUThere]

Just looking at the charging system schematics... Did you check whether the 15A Engine fuse is blown or making lousy connection?

Edit: Oops your post showed up while I was writing this. Are you saying changing the VR back to the old one fixed it?

 

[MiniPigg]

let me go check that now.... one thing that was confusing me was in the schematics for the VR... when you press down the amrature and take readings between IG and E its suppose to read Infinity... mine reads the 10 ohm register. Hows it suppose to ever read Infinity on this test? With it pressed to me it appears to place the 10 ohm resister and the 100 ohm coil in parrallel which would mean it can never read Infinity.. it would have to read at least 9 ohms. Which is what it reads.

 

[Pin_Head]

The issue is whether your battery is actually discharging or not

Drive it around for 30 minutes or so with the headlights on and then turn them off. Check the amp meter: If it has a large positive deflection for several minutes, then it indicates that your battery was discharging.

So what happens to the amp meter when you drive around with the lamps on for a while and then turn them off?

One more thing: The headlights are grounded to the VR via a white wire with a black stripe. Make sure that this wire is in place and it is not corroded. If there is a bad connection between the headlights, which consume a lot of power and the VR, it might influence the alternator power output..

 

[GetsUThere]

let me go check that now.... one thing that was confusing me was in the schematics for the VR... when you press down the amrature and take readings between IG and E its suppose to read Infinity... mine reads the 10 ohm register. Hows it suppose to ever read Infinity on this test? With it pressed to me it appears to place the 10 ohm resister and the 100 ohm coil in parrallel which would mean it can never read Infinity.. it would have to read at least 9 ohms. Which is what it reads.

That's a really good question. I looked at it and agree with what you're saying. So I got out a VR that I had sitting around the garage and took it apart to measure. Mine says 100 when it's open and 10 when it's closed as expected. Pretty sure that one was still good when I took it off.

 

[GetsUThere]

The issue is whether your battery is actually discharging or not

Drive it around for 30 minutes or so with the headlights on and then turn them off. Check the amp meter: If it has a large positive deflection for several minutes, then it indicates that your battery was discharging.

So what happens to the amp meter when you drive around with the lamps on for a while and then turn them off?

One more thing: The headlights are grounded to the VR via a white wire with a black stripe. Make sure that this wire is in place and it is not corroded. If there is a bad connection between the headlights, which consume a lot of power and the VR, it might influence the alternator power output..

Ahh, I think I see what you're getting at (sorry I'm kind of slow at this some times). So that I understand the troubleshooting procedure, you're wondering if in fact the charging system is in fact performing properly, but it's unable to provide sufficient capacity to meet the load of something else that might be wrong. This vs. what I was assuming which is that the charging system wasn't doing anything at all?

 

[Pin_Head]

I'm thinking that the alternator output may be wired directly to the battery and that is why the meter stays pegged to the left with the headlights on. Lotsa people do this with an alternator swap. If it is wired this way, the meter never deflects to the passenger side.

Do you ever see the meter needle deflect to the right of center?

If it is not wired incorrectly and the battery is actually discharging with the headlights on and then charging with them off, it is probably the ground wire from the headlights that is messing things up.

 

[GetsUThere]

Darn.. I was still missing the boat. Thank you for explaining.

 

[MiniPigg]

Ok.. I wasnt able to check the fuse as mentioned above.. I will try and do that today. Right now I am at lunch and only have a few minutes to try and explain.

On the FJ55 the Ammeter is set up a little different as it is displaid on the instrument cluster.


http://www.cruiserland.com/parts/images/55instgauge77.JPG

The Ammeter is on the right side. Not a good photo but I have to be in class in 5 minutes.... You can see the (+) is on top and the (-) is on the bottom. Since I put the old VR back in the needle stays in the center... but when you accelerate the needle goes all the way up to the (+) positive showing it charging. And it stays there as long as you are driving around. It only goes back to midline when you are at idle. The needle still flucuates with the rythm of the turn signals and it still drops when you turn on the headlamps.

got to go... sorry... will try and post more inbetween classes.

 

[Pin_Head]

Your alternator is wired normally, since it indicates both charge and discharge.

Generally, indicating a constant charge (and not returning to the middle after 20 minutes of driving) would suggest that the battery is bad and won't take a charge. The fact that it constantly reads discharge with the lights on suggests that the alternator can't put out enough juice to keep up with demand. Both are unlikely, since they are new.

I am guessing that it is more likely a bad voltage regulator ground. Try running a separate ground wire at least temporarily between the alternator case and the voltage regulator case. Is your ground strap between the engine and frame OK?

 

[MiniPigg]

I placed a ground from the VR to the radiator support frame and then also placed a grounding strap from the alternator from to the negative side of the battery. Did that yesterday. At idle the needle sits at midline. But as soon as the rpm raise the needle follows and stays all the way up at the positive for the entire trip. I thought it was suppose to drop back down after a minute or so to midline (?). So the needle follows the rpm from midline to (+) positive side of the ammeter. It remains there the entire time you are driving down the street/highway. I did measure the voltage across the battery with the rpm up to about 2000rpm. And it went to about 15.6vdc and went back down to about 13.2vdc at idle. With the rpm increased about 2500rpm it never went over or reached 16vdc. I brought the VR back to Napa and they wanted to order another one instead of refunding me my money. Thats one thing I fricken hate about scam-pa. I didnt argue with them this time just incase we all determine the vr is actually bad and needs to be replaced.

 

[theo]

. . . stays all the way up at the positive for the entire trip. . .

How long a trip?
This may or may not apply, but you could try an overnight charger on that battery. It's possible to run a good battery down far enough so the truck's alternator can't charge it in an hour or two. I've done it, and the symptoms were just like yours - alternator trying like hell to dump charge into a drained battery. My case was bad enough to make me disconnect the alternator and drive home on zero charge; wiring and fusible link etc. were starting to overheat. I put it on the charger overnight and that battery is working normally now. Worth a try for you.