Mechanics

RUNNIG CAR'S ELEC. SYSTEMS LIKE AC & A

2004 Honda Civic

Electrical problem
2004 Honda Civic 4 cyl Front Wheel Drive Automatic 84000 miles

This started happpening recently. I was driving on my way back to home from office and my car's ac and audio systems started switching on and off on their own. I could see that this was happening more when my car was at low speed. When I pushed gas padel ac and audio systems were coming live again. I thought I would stop the car once and restart again and probaly that would fix the problem. I switched off the engine but then it did not start again. I had to call road side assistance and they gave me a jump start and my car worked fine for two days after that. After two days same thing happened again and this time right in front of PepBoys, they worked on it for a few minutes and recommended a battery change. Car worked fine after battery change for a few days but today again I faced the same problem. This time I switched off my engine when I reached back home. This time again after switching it off it did not turn on again. But after a few hours when I tried again it started working just fine. I tested my alternator by taking out the -ve battery cable when engine was on. When I did this car remained on. I did not know what is going on. Please help. Thanks very much in advance.
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Naudiyal
June 2, 2010.




Hi naudiyal. Welcome to the forum. You dodged a serious bullet. Removing the battery cable is a trick that was done many years ago by mechanics who didn't understand how to diagnose electrical systems. Doing that can allow system voltage to increase to unsafe levels that the voltage regulator will be unable to control. There are a lot of computers on your car that can be permanently damaged by high voltage. If you increase engine speed with the cable removed, it is possible for some systems to reach 35 volts. That will destroy every computer on the car and burn out any light bulbs that are turned on.

It sounds like this is an intermittent problem so any testing must be done when the problem is acting up. The brushes in the generator could be worn causing an intermittent connection, but 84,000 miles is a little soon to be expecting that. It is more likley there is a loose connection where the negative battery cable bolts to the body or where the positive cable bolts to the fuse box.

Also be aware that Hondas have a really bizzare charging system. Every electrical item on the car is monitored, then the generator will provide only the calculated amount of current all of those things should take. Any aftermarket accessories such as a radio, cell phone, or amplifier are not monitored so the battery will have to make up the needed current. That will result in the battery gradually being not recharged enough while driving. The symptoms you described don't exactly fit this part of the story though. If you can catch it when the engine won't start, the easiest way to troubleshoot this is to use a test light to follow the battery cables until you find where the voltage is lost.

Caradiodoc

Caradiodoc
Jun 3, 2010.
I forgot to mention that everything works fine if I do not turn on my ac. When I turn on my ac and apply breaks it starts giving me the problem I had described. Does that make any difference in your opinion?

Thanks in advance!

Tiny
Naudiyal
Jun 3, 2010.
Do you mean if it doesn't start, it will if you turn the AC off? Also, when you say " doesn't turn on", do you mean the starter will not crank the engine or the engine cranks but will not run? If it doesn't crank, does it make any sounds such as a rapid chattering or buzzing sound?

It really sounds like the battery is not always being recharged while driving or there is an intermittent connection. If the generator is intermittent, when it stops working there should be a warning light on the dash or the voltage gauge will drop down a little.

I don't know why turning the AC off would help unless the compressor clutch coil is shorted and affecting a circuit that is tied in with the engine's electrical system. The way to prove that would be to unplug the clutch, turn the AC on, (which won't cool now), and see if the problem still occurs. There still could be an intermittent connection. The AC system could be drawing additional current that makes the bad connection act up. If that's the case, the problem will gradually get worse until it even acts up with the AC turned off.

Caradiodoc

Caradiodoc
Jun 3, 2010.
Yes it would start if I wait for a let's say 15 minutes, turn my ac off and then try starting it again. When it does not start it makes rapid chattering sound.

I do not know a lot about cars but could it be alterntor? I am taking my car to workshop tomorrow.

Tiny
Naudiyal
Jun 3, 2010.
Yup, most of the symptoms could be caused by the generator but after rereading your original post, I still have a feeling it is a poor electrical connection. The radio and AC system can stop working when the battery starts to run down but they could also be in a circuit that has a poor connection. The chattering sound indicates low voltage to the starter motor but that too could be caused by a run down battery or a bad connection. To add to the confusion, a run down battery can in effect, self-recharge enough to start the engine after it sits for a while.

The best thing you can do is to observe as many clues and hints as possible to help your mechanic because intermittent problems are always frustrating. When the problem occurs to the radio and AC while you're driving, do the head lights also dim? Do the turn signals behave normally? Do you have a voltage gauge on the dash or a warning light, or both? What does it indicate while the problem is occurring?

It is even possible all of these things are caused by a cell that is shorting in the battery. Usually the short isn't intermittent but it isn't unheard of.

Caradiodoc

Caradiodoc
Jun 4, 2010.
Today I took my car to a auto repair shop near my home. He said alternator is bad. He changed it. It did not cost me anything as I have warranty on my car. When I reached back how I observed that he has even changed the cable that connects to the negative point of the battery. May be there was a loose connection and even alternator was bad. My car is working fine now. I would post again if I see some issue again.

Thanks very much for your help!
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Tiny
Naudiyal
Jun 4, 2010.
Happy to hear the good news for now. I suppose if I guess at enough things, I have to be right about one of them. : )

caradiodoc

Caradiodoc
Jun 4, 2010.

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