Honda Civic '96, D16Y5
Alternator is stock (Mitsubishi)

This is something I just found out. I've been having high RPM issues and no cooling when stuck on a traffic jam during a hot day. The speed will suddenly go up to 2000RPM idling or moving. It goes away as soon as I have the car running faster, so maybe the outside air naturally cooled down the engine bay and was was helping whatever is overheating. So I soon found out that there's no cooling since the compressor clutch isn't engaged when it happens. At first I thought RPM was high because the thermal protector of the compressor tripped and the ECU doesn't know, because it's basically still supplying voltage to it. Note that A/C switch is still on. Based from the wiring diagram in the manual, thermal protector is independent so everything made sense and maybe I just need extra cooling in this tropical country. Was planning to upgrade the condenser fan to a stronger one that moves air better.

But out of curiosity and just by chance I was able to replicate the issue on my garage a few hours ago and tested batttery voltage when the increase in RPM happens. Good lord, I measures more than 18V!! A/C clutch not engaged (not turning) and A/C switch is on. Tested multiple times to verify. If I switch the A/C switch off battery voltage goes back to normal. Turn it back on and the voltage surged again. This until the open hood caused the engine bay to cool down. How on earth can that happen? Why would it draw that amount of voltage when engine bay is hot, when the clutch isn't even engaged and a regulator is installed in the alternator? What could be the problem, the alternator or the compressor? If its the alternator, should 18V supposed to disengage the clutch? Why is the A/C the only thing affected? If it's the compressor, how can it affect battery voltage when A/C is on but clutch is not engaged? I've never been this lost in terms of troubleshooting.

 

I didnt read the whole post but if voltage is spiking its the regulator inside ur alternator

 

Why would the voltage surge then only when A/C is turned on? And as soon as the engine bay (not sure which component really is acting up during extreme heat) cools down, it gets back to normal.

As far as I know, resistance increases as temp increase so voltage should go down.

 

During my attempt to recreate the symptom this morning my compressor released a lot of white smoke (must be refrigerant). I pressed on the gas pedal, maintained 3000RPM in hopes to make it happen again and film it. But the high pressure in the compressor vent out on the relief valve. I was never able to replicate the 'high RPM, high voltage' condition.

Could an overcharged A/C system create a voltage spike?

 

Okay, I made my system undercharged. I have managed to recreate the problem. This time, when the RPM increased, A/C clutch disengaged, and I measured battery voltage, it's 15.3V. It really seems like a voltage regulator issue.

But, my question now is, why did the A/C clutch disengaged? Can't 15.3V not power the coils of a 12V relay? What about the other relays in the car? Am I not only noticing that they are also affected?

 

Change the alternator ******

 

Forgive me for having to post this poor diagram, I just thought people will get bored reading a long post about a topic that is already confusing and doesn't seem to make sense. I need answers before I replace the regulator, please!





Is there any relation you can think of on why does the temperature and A/C on combination affects voltage and causes the RPM to rise and the clutch to disengage?

 

Thanks for the input smartass

 

Don't start a new thread just post in your other one.

 

I told you 2 days ago to change the alternator


Youre still here with your dick in your hand

 

I'm convinced the voltage regulator is bad, Einstein. What I'm asking from my very first post is the relation of the high RPM and the A/C malfunction to that voltage surge and ambient temp.

Empty can is always noisy.

 

You calling me Einstein isnt an insult when youre trying to figure out why a voltage surge is making components act weird

Swap the alternator stop posting

 

Yeah double posting is a no no.

 

Fixed.

 

Don't tell me when to change my alternator, I will have the regulator replaced when I have the time, this car hasn't been my daily driver because of the A/C issues.

Now I have the time to ask and post questions here. Yeah, yeah, components go bad when voltage isn't regulated, Einstein, but why only the A/C? The A/C relay, is right between the condenser and radiator fan relays, why would the voltage surge not affect those? I wanted to make sense on that matter, and it's relation to the high RPM.

Why am I explaining to an idiot, who mentioned on his first reply that he didn't read the whole post, but had the guts to call me names. You the one that should stop posting in this thread, Einstein.

 

Heya, thought this might answer a question or two...in any case, your compressor clutch WILL disengage under certain conditions..i.e. abnormally high temperature load, excessive/inadequate "freon" R134a/R12 pressure, a worn clutch mechanism, a loose compressor clutch wire, or a short/broken wire in the A/C clutch circuit. Manufacturers tend to build safeties/redundancies in certain parts so that whenever something temporarily approaches breaking point it wont continue to go critical and simply grenade in your engine bay. This often leads to intermittent halts in the operation of said components which confuse owners as to why something that was working great last week suddenly "randomly" (or under specific conditions) craps out on them, when essentially it is just a systems way of screaming " TROUBLESHOOT ME" when it can't communicate with the ECU and throw a code at you.

 

Okay you two have had your fun at poking each other, one a little harder than the other.

I get why the retort as OP didn't swing the first punch. turbohatch96y7, quit throwing punches. If you don't you will see a pretty hefty infraction for overly rowdy behavior, or conduct unbecoming of a fellow human being. This isn't GDD so curb your GDD attitude at the door. Thanks.

Now lets keep this a civil and considerate discussion. There is nothing wrong with OP wanting to get a deeper understanding of why the behavior exists.

Anyone can swap parts, understanding WHY the parts act as such is another matter and takes a lot more thought and consideration.

 

Okay, here's some development. I brought my Civic to a reputable shop (which only works on nothing but Alternators) and have it diagnosed. I gave the tech and the shop owner a heads-up that the regulator is bad, as I'm getting an overvoltage condition and I want it replaced. I told them about the A/C situation and they immediately tested the alternator. They said it look good, but I insisted it's bad, that it's hard to replicate because the engine bay must be really hot and the A/C should be working for a while in the middle of a traffic jam when it happens. In any case, it must be a bad regulator, right?

The owner agreed but didn't hesitate to tell me he is skeptical that the alternator or regulator is bad. He said when regulators go bad, that means there's one or two shot diode, it fails to deliver regulated voltage all the time. So they tested the regulator terminals and failed to get battery voltage on the IG (Ignition) terminal. They said they're not taking my money and wouldn't replace the regulator. It's all good aside from a blown fuse (underdash #15). Okay, sounds good, he must be telling the truth because who wouldn't want to sell something right?

But since I have diagrams printed out, I was like, WTF, if Fuse#15 is blown, I would have get all sorts of issues. MIL. No Charging light etc..



He was quick to tell me to not believe the manual, because we are in the Philippines and Civics were built differently. He told me I don't have an ELD. He was right. I was beginning to think my whole life is a lie.






So this diagram does not apply on our case. I would have to verify why I still get the charging light if Fuse#15 is blown and what's turning it off when engine is running. I suspect it's directly wired to the ignition (red) but we'll see.






Back to the issue, I asked him what's the connection of the overcharging to the that blown fuse and the high RPM-disengaged A/C clutch condition? He said it's because the system isn't closed loop. Since we don't have an ELD, the alternator relies on the battery voltage from the ignition switch. If that line is open the regulator won't know what the battery voltage is. I'm not sure if I believe that but I have to admit it makes sense.

He then asked me where the A/C clutch relay is. I told whim where it is and he removed it while the A/C switch is on. Voila. RPM increased and no cooling, of course. He explained to me that since the ECU is getting an A/C on signal, it is also throwing a signal to the FR terminal on the regulator to increase the field voltage. But with the sudden loss of load (A/C clutch), the voltage spikes and the regulator won't detect it because Fuse#15 is blown. Add the steady high rpm (ECU thinks A/C is on) and voltage will remain high because the extra current is not being dispersed to the clutch coil.

Again, it made sense, but I'm not 100% convinced since there aren't diagrams I can rely on. I guess I have to verify the regulator wiring myself. I will just observe if the same issue happens again. If it does, I'm definitely having the regulator replaced regardless of what he says. I appreciate his honest business and I believe he is sincere, but god damn it I'm tired of this issue.

P.S.

Sorry for the long post.

 

I forgot to mention that I did replaced the A/C clutch relay. Maybe it's the one going bad when the engine bay gets too hot. Pretty sure now that the high RPM and no cooling happens because of it.

 

Canadian Civics in the 92-95 don't have an ELD unit. That wiring guide might be more useful to you as you also don't have the ELD.

 

If you have the manual, hope you don't mind if you will post the diagram here or send it to me? Thanks!

 

Add car information - required for all tech threads - to your first post.

 

You're gonna have to do some insane testing as I'm really interested in this setup. Not interested to use it but interest in how it works like that, also the part # to the oem alternator as well.

What you can do is basically continue driving it but monitor the batteries voltage level throughout your driving, you'll have to wire your DMM directly to it. See where does your revving begin at what voltage and when does it stop. How long does it stay revving that high? I would assume it would go up about a couple hundred rpm's but all the way up to 2200rpm, interesting.

edit: also confirm that your factory wiring is somewhat similar to that diagram by checking continuity to the wires.

 

Ooops. Done.

 

because it has to control the voltage under conditions where the computer is asking for more current, and if it's going out, it's not able to do this, replace it quick, hope you haven't already done damage, as soon as you saw voltage that high, you should have immediately shut it off