19rxseven87

Hi guys,

The problem is that my alternator won't charge above 13.8 ish at idle and 13.7 ish at throttle. There is belt dust that forms around the alternator, the alternator was replaced multiple times finally back to a used OE one. Ones from autozone were POS and wouldn't even charge past 13 volts.

I'm confused at what this problem is. I can charge the car overnight with a battery charger, run the car for half a day then I start needing light jumps to get the car started in the evening after a while. I had the alternator off of the car before I put it in and it tested fine at autozone.

Can anyone help with this? I've tried searching but not quite sure what to check for. I'm not sure whether or not it's the alternator again (though it tested fine at autuzone), the battery is good (newish one, tested good), a problem with the fan clutch, a problem with the water pump (it does heat up pretty hot during the summer, probably 3/4 up). I've had all of the grounds re-grounded, and the battery terminals replaced. Starter is newish as well.

Thanksin advance for input.

dwb87

iTrader: (22)

Seems like the alternator is fine.

Check for a drain... Remove the negative battery terminal, set a multimeter to AMP current (mA), one prong to the negative car terminal, one prong to the negative battery terminal, BE SURE ALL ELECTRICAL LOADS ARE OFF, now see if the multimeter is reading very very little current (mA) or zero... If it is displaying more than it should be, remove the 60A BTN fuse from the engine fuse box (so that you can open the door of the car without the lights coming on), go into the car and start pulling fuses from the fuse panel by your feet, one at a time. If that fuse doesn't get the multimeter to display zero, then put it back in and try another fuse. You can also try pulling other things... The way I found my drain, was by unplugging my turbo timer. The multimeter then displayed zero, and that's how I knew that was the problem.

dwb87

iTrader: (22)

Is there any damage to the belt? (Cracks, grease, etc...) - Is the alternator belt properly tensioned?? The pulleys do match up... Right?

19rxseven87

will try this, thanks.

no damage to the belt, no cracks, no grease etc, yes the belt is properly tensioned, albeit on the tighter side, pulleys do match up.

19rxseven87

checked for a drain, no drain.

retensioned the belt.

also, checked the b+ terminal at the back of the alternator. it is putting out 14.00 to 14.1 volts at idle but it won't go up as rpm increases.

bad alternator, again perhaps? if so, i have had 4 bad alternators in a row? maybe just very bad luck?

satch

iTrader: (1)

You might have a problem w/the starting circuit that relates to the wiring or components not including the battery and alternator. When you need a jump, instead take a wire and run it from the positive battery terminal to the Black/White wire at the Starter Cut Relay (found on cars w/factory alarm and has only one plug to it) or the Black/White wire found in a Blue plug near the trailing coil. Doing this will bypass a number of connections as the B/W wire runs to the starter solenoid w/only one connection in between. When you use the jumper wire the starter ought to turn over immediately. See in the future if this makes any difference at all. If there is a stark/noticeable difference then you will be able to further narrow down your problem.

19rxseven87

what gauge wire should i use? so instead of using an external jumper source such as a jump box, just take a wire from the positive terminal to the b/w wire near the trailing coil?

i've noticed that after the car is run for a while, when it doesn't want to start, it is pretty sluggish in turning over the car, but when the car is fully charged it turns the starter immediately.

19rxseven87

also when car is warmed up, with the head lamps on, it is only charging at 13.3 volts. yuck. from the B terminal it is putting out 13.7ish volts but battery only charging at 13.3. should i bite the bullet for a higher output alternator?

bumpstart

run an extra B+ wire from alt to the battery

if you have mix matched a s4 alt onto s5 car or vichy versa without appropriate changes to the field switching you WILL get battery issues

one way trickles all the time the engine is off,, the other overcharges and boils the battery

adding s5 alt to s4 car also requires the B+ upgraded as the B+ is marginal already for the amperage

19rxseven87

should i fuse the additional b wire or just add it to see if it will help with the charging?? the alternator is an s4 alternator, not an s5 alternator. the car is an 87 rx7 tII (probably should've mentioned that)

satch

iTrader: (1)

What was suggested was to "only" diagnose your problem. If you did what was suggested it will bypass some elements to check to see if there are issues besides the alternator/battery. This is just to check to see if the starter would turn over w/o any problem. One end of the jumper wire to the positive battery terminal and when the other end touches the B/W wire the starter should turn over as if you were starting the car.

19rxseven87

noted, thanks.

any other suggestions? i've connected the b terminal at the back of the alternator directly to the positive battery terminal and it seems to be charging better *knock on wood*.

19rxseven87

bump. i've noticed that when the car is cold the car seems to charge better than when it is already warmed up. any suggestions as to why this could be?

88_N/A_GXL

iTrader: (3)

It being cold and charging better is just because hot electronics lose efficiency.

manbeast

is the belt dust from the alternator being tensioned too tight? my alternator belt has done the same thing. also not holding a charge.

19rxseven87

no, the belt is not tensioned too tight, in fact it's maybe a little on the looser end. i can see it wobble up and down more so than my other belts.

is there any fix for this heat? because i've noticed that it gets so hot right now (in the winter time) and i don't think it'll charge well at all. i'm thinking this heat is from the creation of this belt dust.

dwb87

iTrader: (22)

Don't you have another thread asking about pulley alignment?

manbeast

yea mine gets hot as hell as well. sounds like we are in the same here almost exactly. im going to go charge my battery tomorrow and trouble shoot ill post anything useful

manbeast

i jumpstarted my car this evening and with a voltmeter it read 14.2 on the battery terminals and 14.4 for the alternator while it was running. and when off it was at 11.8 for both. isnt it supposed to be at 14.6 at the least while running and above 12.0 (not sure) while turned off? after i let it run for 10 minutes i tried to start it up again of course it didnt start it started to drain the battery i watched as the idiot lights got dimmer every time i tried to start it. it was sluggish and more sluggish after each attempt also it did click a couple times. not every time i turned the key just a few. the car starts just fine when the battery is fully charged. when i jumpstarted it tonight it didnt start up right away i had to let it sit for about 5 minutes so there definitely is a drain. does your car have the same symptoms? I searched threads on here and found some that go through this and one way to find the drain i thought sounded like a good way was to hook up a test light to the battery i think positive terminal and pull the main fuse (not sure) and if the light is turned on (do not turn key over) then you have a drain and to find it you need to start pulling fuses one at a time from the fuse box next to your feet or start dissconnecting wires one at time, also i read in an australian forum that the headlight flippy motors can be pulling power when car is off. anyways let you know tomorro

MIDNFauciUSN

iTrader: (8)

14.4 is normal while running. 11.8 is normal while off. 14.4 while running at least tells you that your alternator is pushing voltage to your battery. If your battery wont stay charged, but your alternator is sending electricity to the battery, suspect the battery. I say this under the assumption that there isn't an insane drain somewhere.

Finding out whether or not a current drain exists is not, in itself, exactly rocket science. Anyone with the most basic knowledge of a DMM can tell you that. Finding out what exactly is draining the current takes a little bit of time though.

manbeast

does anyone happen to know the battery requirments for a n/a s4 rx7? i have a 650 cold crank amp battery not sure on all the other info. but it was the battery it came with when i bought it and i went and got a free replacement from walmart cuz it still had a warranty.

19rxseven87

manbeast- yes, my car does exactly that. i don't think it's a drain because if the car is left sitting there, and started up cold, it charges perfectly. once it starts warming up the engine bay the charging starts to go downhill. there is belt dust buildup at the pulley and i am guessing that the friction caused by creating the belt dust is heating up the alternator much faster than radiant and convective heat created in the engine bay.

dwb87- yes i do have a question about pulley alignment, but after putting a straight edge to the pulley i dont think it is deviation side by side, rather up and down

dwb87

iTrader: (22)

I do NOT believe that you're getting so much heat from belt dust. Perhaps you should get that out of your mind. UNLESS your alternator is not properly aligned. Even then, it can't produce THAT much heat.

Concentrate on the alternator and the alternator wiring. Especially the wiring.

19rxseven87

have tried 3 different alternators. I can take a picture of the alternator alignment or maybe even a video to show the alignment, but honestly the symptoms say that the alternator charges better cold than warm. i will try another alternator though..

dwb87

iTrader: (22)

Nah, you don't need to spend more money... My alternator did this a little bit. Not as bad. Seriously, checking the wiring. Do some extensive research with your multimeter.