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Discussion Starter · #1 ·
I have been trying to pinpoint this problem for awhile now: When my car is started, the voltage jumps around from anywhere to 12.0v - 13.2v. When it gets down to 12.0v, the Hold light (I have a ATX) flashes and keeps the car in 3rd gear cause it to rev up and also cause my car to overheat really bad (just about all the way to the H on the Temp. Guage). I have brought the alternator to get it check but it check out good. I know there is something drawing power out of the battery because when I take either of the battery terminals off and put it back on, it creates a big spark. I put a multi-meter on to test the amperage and there is a 0.400A draw when the car is off. I don't know if that would affect the voltage that much if the car is running. I have checked the grounds and cleaned them from corrosion, popped each fuses one-by-one and still no luck. I am wondering if there is some type of malfunction in the alternator drawing in too much power or could it be something else?

And while I'm posting, I'll post another problem. I have my boost @ 11 psi and when I W.O.T., the car starts stuttering (chugs along) almost like it's not getting enough fuel but I don't hit the boost cut because there is no warning beep indicator. I have a tiny crack in the Throttle Body Boot but sealed that with silicone sealant and plus it's at the top above where the clamp goes on. I hear a lot of hissing from back near the Throttle Body but all the vaccum hoses appear to be good. There is another hiss down by the charge pipe and upper IC hose but but everything is on secure and the hoses were taken out and appear to look in good condition. I know the Bypass Valve leaks a little at idle so I don't know if that is causing the hiss.

Sorry for the long post, I will try to separate it next time when I have more time
 
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Whoever checked out your alternator sucks. Replace it.

And I think you answered your own question on the boost question. Remember that the rubber flexes and stretches under boost, causing small cracks to become large cracks.
 

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Discussion Starter · #3 ·
I have taken the alternator to a highly reputable shop in this area which specialize in electrical components in vehicles. And also I took it in to AutoZone and both came back checking out fine. This sounds like a stupid question but does a bad ECU effect electrical components?
 

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Sometimes an old alternator can be a bit flaky; sometimes it will work just fine and other times it will not. If the alternator is connected correctly and the voltage at the battery is less than 13.5 volts at idle there is a problem with the voltage regulator (inside the alternator).
 

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Discussion Starter · #5 ·
Thanks for the all the posts. I brought the alternator to another shop to get it checked and the alternator was only generating 8 volts when there was a load put on it. I bought a new alternator yesterday just in case it checked out bad so I will put it in today and post the results.
 

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Discussion Starter · #6 ·
Put the new alternator in and the same results...the voltage jumps from 12.5-13.1 volts. Anyone have any suggestions?
 
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Always bench charge your battery after an alternator replacement. A battery that is ran down by a bad alternator is the cause of a "POS rebuilt alternator" 90% of the time.

So, charge your battery fully with a good charger, or get a new one.
 

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You say there is a 400 mA draw when the car is off? I've never checked my car, but that sounds like too much.

What you could do is pull every fuse one at a time while checking your current draw and see what is contributing to the 400 mA. Some will make sense (you would expect some current draw from the radio to hold the preset memory, etc), and hopefully one won't. That should narrow down the search some...
 

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Discussion Starter · #9 ·
The "Lights" fuse is the one drawing out power. All the dome lights in the car go off when the door is shut. Does anyone know if there are other things connected to that fuse?

I've charged the battery before putting in the new alternator and it still reads out almost identical to the old one. I have an Automatic Transmission and it's electronically controlled, am I right? Is anyone familiar with the automatic transmission and could that be drawing in a lot of power? I have taken it to 2 shops and they both did tests on the car and they said that the alternator is bad. I've taken my 1st (origional), 2nd, and 3rd one in to 2 different places to test them out and they all read out at 14.9 volts. So the alternators are good (in the process of getting the first one back) and I am getting really frustrated with this. I'm almost thinking about giving up and look for a new car (almost)
 

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I don't know of any fuse called "Lights." There is "HEAD" for headlights, "TAIL" for taillights, "METER" for the dash lights, and "ROOM" for the interior lights. Now I'm mostly familiar with the 90-92 system, and the 88-89 might be slightly different. Which fuse are you talking about? Is it in the box under the hood or under the driver's dash?

Also, have you taken a voltage measurement yourself with the car idling? What was it? If not, you need to go buy a multimeter and take readings at various times to really see what's going on.

Is the alternator belt tight? Is the battery to alternator cable and the two-pin regulator/dummy light connector plugged in securely? The "CHARGE" light in the dash should be on if the alt is putting out that low of a voltage, unless the regulator IC is shot (internal to the alternator).
 

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Discussion Starter · #11 ·
Sorry for the misinformation. The fuse that is drawing the .400A of power is the "ROOM" fuse. Do you know what is all connected to that fuse?

I have put a multimeter on the battery when the car is off and it reads at 12.6 volts. When the car is running it reads anywhere from 12.0-13.0 volts. The 2-pin connector on the alternator is on securely. The Charge batter light on the dash does not come on when the voltage gets down to 12.0 volts but does come on when the keys are in the On position. I've heard that that light shouldn't come on until about 11.0v or so. I'm wondering if it is something to do with the Automatic Transmission since the only light that is flashing is the Hold button. The AT is electronically controlled and I've heard people with bad alternators and a manual transmission having their brake lights and such flashing as opposed to just the Hold indicator light on my automatic.
 
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If I'm not mistaken, your stereo's clock runs off the room fuse.

Also, did you make sure to tighten the hot line connected to the alternator nice and tight?

Also, the flashing hold light is your ATX tranny computer trying to let you know that it has stored codes.
 

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Stuff on the "ROOM" circuit:

CPU (interior light timer and sound warning unit)
Interior Light bulbs (all of 'em, including ignition key illum, trunk light, except instrument clusters)
Power antenna motor
Radio (iillumination), Clock
ATX Shiftlock system (integrated into base of shifter)
EC-AT control unit
Security system
ECU (engine control unit)
 

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...I thought I would add that the factory workshop manual specifies "less than 20mA" dark current, so you've definitely got a problem with 400mA draw with the car off.
 

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Discussion Starter · #15 ·
Yes, the hot line is on there tight. And per your comment (FlySwat) about the AT computer signaling codes when the Hold light flashes, I don't agree. Unless the intervals of the flashes are the same as the ECU codes, the flashes are quick and abrupt; the intervals of the flashes will also fluctuate. The flashes usually occur when I'm driving. This is probably not important but when the flashing occurs due to the low voltage, my car heats up sending the needle on the Temp Guage to go 3/4 of the way to the H. I wish more of you were familiar with the automatic transmission because this is frustrating :(
 

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The EC-AT computer has it's own set of codes. I am not an expert on the ATX, but I believe you need a special tester to pull codes from it. Usually you need to jump a diagnostic connector to get it to spit out codes; it won't just give them to you while driving (same with the check engine light).

Also, I just don't see how low voltage would cause the car to heat up (unless it is preventing your cooling fan from coming on). That sounds like a separate problem.

You need to get a Mazda Factory Workshop manual if you want to diagnose these electrical troubles. It will tell you everything you need to know about pulling codes from the EC-AT computer and its operation. Otherwise I would consider bringing it to a Mazda dealer as they have all the special equipment and manuals there to diagnose the problem.
 

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Discussion Starter · #17 ·
I have scheduled another appointment at a Mazda repair shop (not the Dealership - don't trust them as much) and I won't be able to get in until Thursday. When the voltage is around 13.0 volts, the needle on the temp gauge doesn't even go to the "M" in Temp so I'm guessing the low voltage is screwing up the cooling system somehow. One of these days I will get the Mazda Factory workshop manual but I'm not doing any major work on it right now so when I decide to do work myself, I'll look in to buying one ($100 is pricey)
 
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The coolant temperature sensor is a temperature variable resistor, Having a low voltage going into it, will affect its output, causing the gauge to read incorrectly of actual engine tempature.

I pulled this from the faq, it tells the impedance of the sensor as relayed to the gauge.


The sensor is a resitor that graduatly chances it value when it gets warmer. it is 233 ohm when cold. and around 16 Ohm when your car is really hot!. So you are not going to measure power there because it is ground. what you could do is measure the difference in volt between the + pole of your battery ant the top of the sensor. it should go down when gettin' hotter .


Here's youre grocery list for radio shack.

resistors :
-233 Ohm
-104.1 Ohm
-21.1 Ohm
-16.1 Ohm

They probably don't have the exact values but maza just used those extreem precise values to make us by an sst i guess.

what you do is the following
disconnect the connector from the sensor




disconnect the connector from the sensor

put one end of the resistor in the connector

now put the other end of the resistor to mass

according to the resistor you took youre gauge should read accordingly



so if you use
233 ohm it should read coldest (first stripe),
104.1 ohm it should be in the begining of the working area
21.1 ohm it should be in the end of the working area
16.1 ohm it should be in the last stripe (overheated)

so if your gauge works correct you know it is the sensor and if the gauge is off it's the gauge ..

keep it cool
 

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I would think the voltage would have to be extremely low to have that much of an impact. If the engine is warmed up, and you have the key to "ON" (engine off) the temp gauge reads normally at battery voltage (12.6 V) vs 14.4V it is supplied with the engine running. I wouldn't think 12.0 volts would affect it that much. I'll have to look at the schematics later and see...
 

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Discussion Starter · #20 ·
The overheating isn't that big of a problem...it's the electrical issue. When the voltage drops (down to 12.0 - 12.4 range), everything else seems to fail (cooling system and AT tranny). Thanks for looking all that up for me :)
 
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