the alternator is putting out 19.7 volts ?

Asked by Jan 22, 2015 at 08:47 PM about the 2002 Mazda Protege5 4 Dr STD Wagon

Question type: Maintenance & Repair

alternator is putting out 19.7 volts have replaced it 3 times what could the problem be

26 Answers


Are there other indications ? is your battery cooking? Is your reading being taken with a good functioning high quality DVOM that has a fresh battery? Have you altered the vehicles wiring?

yes the battery is boiling over, and no haven't messed with the wiring and yes checked with a good muilt meter, it starts out @ 14.7 v within 3 mins its up to 19.7 volts this is my daughters car and i don't know much about mazzda's

2 people found this helpful.

The voltage reg. should kick off at like 14.6v warm, Does the part store find fault after testing each time? and give you a replacement they just tested? If not able to, get tests from another part store to verify regulator functions correctly. I know this is not the best available reg. you can buy, but suggest proving you have numerous failures. Part stores can get reg.'s to sell separate. Or I get mine from the rebuilder shop in the city.

also i replaced the battery with a new one thinking that it maybe shorting out, checked the wiring to to battery to alternator and its fine ! HELP

3 people found this helpful.

If this is some malasian or chinese part? or even from mexico ? You may have to try another supplier's reg. after testing to verify. bad batch? or is there some underhood problem damaging each one

yes they were benched tested ea. time the first 2 were bought at o'rileys and the third one at napa

cpu problem or is there another regular somewhere else?

it did blow out her headlights weird


Who made the volt. reg. that is currently in use?


where is the epu located

1 people found this helpful.


Thanks anyway


You could get a used Oem part at pik-n-pull and solve it? I have solved several vehicles this way but havent seen a reg. stick like that since went to the dealer. Quit using anything but Oem after learning the redundant circuitry of Oem. Does yours have a small cover plate for inspection? Some makes you can see what they put in, aftermarket prob. no


The alt rebuilder shop uses ones they believe in. 15-20 bucks, that's half price of napa for just the reg.

I'm having the same problems you are having did you ever get a solution


it is up to the circuit board to cause an open. That is in the voltage regulator. If a car's battery smells, oozes, vents, it is a sure sign its being cooked. The alternator and reg are sold together, they can also be rebuilt at a rebuild place, for starters and alternators. If you find a good one at a yard, you can test it at the parts store. wiring and connection issues should be looked at first, fuses protect circuits but not in the situation where the regulator circuit board is at fault. Depending what part is installed in your vehicle now, you may need to consider finding the higher quality type to use. I find the original was the best and lasted. The kind they sell remanufactured may carry a lifetime warranty and you can just keep putting theirs in. If you get used parts, try and get the alternator harness with. part stores may offer it for some if you request, but again, the original was the best and has fewer problems lasting the longest. another, from a car without problems, gives you what lasted. You inspect your parts and your harness, you consider your conditions. Has there been overheats ? is there an exhaust leak near the failed part? can you find a service bulletin when you search for your vehicle information at the public library or online? If you want to fix your own, you can inspect for causes of failure, put brushes and a regulator in it, check the bearings etc. ZIf you are not mechanically inclined? The lifetime part provides coverage even if you damage the new one from not doing the installation correctly. so it becomes your choice to make.


(If you are not mechanically...) excuse me. A diode bridge inside an alternator can also cause it to get stuck, in that event, the testing during teardown would reveal it. The motors manual or chilton's manual at the library has always been where, during diagnosis, we could identify the one in use and see the tests for what goes wrong. there are drawings and wire diagrams that are specific to that type part where it gets used. some simple tests for overcharge can be found there and tried to decide before you take it apart and during inspection. Each one is different and fails differently, or the brushes wear out, or it gets damaged. That's what you can think about with your car. Is it the parts fault? is it worn out? or did it get mistreated or damaged. testing it at the parts store is the least amount of brains needed and the fastest.


Having the battery tested....Before testing for overcharge and rushing off to get a few things, a battery thats being treated like that needs to be checked, remove it, take it to be checked with a hydrometer, see if the cells read even, you can suspect charging it is unnecessary, and smoking is a nono. Take it to be inspected and tested before reusing it. Further damage to it can cause an explosion. If its indications and readings are not that of overcharge it could mean that your test equipment, method, or the alternator are intermittent and or causing you conditions requiring professional help. Both items can be tested by many parts stores. A battery with problems can make false conditions or readings occur.


An alternator can get damaged in such a way that it can only be found during live assembled testing by a technician. Those can have a winding issue. a failed or damaged one takes experience to determine and prove. If you suspect that kind of failure...get it outta there. It can be a danger to leave it connected. Again, in this event, testing by qualified personnel is the best. Leaving the battery connected while unattended during this kind of electrical concern is NOT recommended.


2002 mazda protege.....I would see what the parts store testing revealed first........if there were questions without answers there, I would continue to a tech or go get parts of my choice to try. I would always have the option of replacing both and getting a warranty or researching the problem about the make, model, year, and which alternator was in the vehicle.


With repeating failure of the same part, it does beg the question...who is doing your diagnostic work and research ? Whose part are you using ? do you have the right service manual for the car? what does research about bulletins and recalls have ? Harness failure? part failure? or damage ? or even as simple as system prechecks from the service manual and previous repair by individuals who are not qualified.


The next seemingly understood, obvious issue that gets people to throw wrenches is buying foreign made tools, failing to maintain your tools maintenance, and using it enough to know the difference, bad practices, Trusting foreign makes, Having equipment made overseas repackaged as a "Good Name". Where I come from, you buy test equipment from a small company in Oregon. When you dont,wont,or cant, you have several and compare them. You compare on another vehicle. you go ask someone to check it who does have known good test equipment. You use the service manual, you look things up, you check recalls and bulletins first, you ask your vehicle's dealer. When you minimize the importance of quality people, material, and equipment, it eventually makes you spend three times as much saying dumb things like, nope, cant be that....Then you want a guarantee replacement part, they should help you, but their tester is made in wing ding bing bong, so there you have it. the prices go up anyway , because of all this, so buy a quality one, or, ask a quality person. They would probably help for nothing just to see right prevail.


That takes you back to what I said in the first few postings. hope you get some qualified help.

Did you figure out what was wrong?

Is not the alternator, is not the ecm or the battery ... What can it be? My Mazda CX-7 has this issue and triggers all kind of lights and codes as I accelerate.

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