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New alternator/uneven idle


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30 replies to this topic

#1 Sweden

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Posted 20 July 2005 - 09:01 AM

Good afternoon from Sweden.

I installed a new (rebuilt) alternator and belt in my 1996 Legacy Outback about a week back. It solved the problem with the brake light and battery light on the dash board, which relieves me greatly. Now I have the problem of the car not idling steadly (it fluctuates slightly). This problem started directly after I installed the new alternator. I also noticed that what I assume is the A/C pump kicks in very often without the A/C being on. What's up here? Did I get a bad alternator or install something incorrectly. Everything looks o.k., but it doesn't sound o.k...

I forgot one thing as well...
The lights (headlights and dash lights) dim slightly when the engine idle starts fluctuating. I notice it at night. I don't receive and problem lights on the dash though.

Thanks for the advice beforehand!


Sweden

#2 Cougar

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Posted 20 July 2005 - 06:35 PM

The reason the brake and battery light came on is because they are in the field circuit of the alternator.

If you disconnected the battery while you did the alternator service the idle problem may be due to the ECU lost the data it stores about the engine. There is a proceedure about letting the ECU reprogram itself. It should be in the owners manual I think.

I don't know why the AC compressor would be coming on if it is turned off. The alternator would not cause this to happen though.

#3 Sweden

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Posted 20 July 2005 - 07:35 PM

I'll check for the info on reprograming the ECU. Thanks!

What would be the symtoms of having the wrong alternator in the vehicle now? Might these be the results? I spoke with the guy who sold me the rebuilt alternator here and Sweden and he stated that it wasn't the exact same one as the orginal. I am wondering if it might be a weaker or stronger one that was in the vehicle???

Sweden

#4 Cougar

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Posted 23 July 2005 - 11:24 AM

An alternator that has less capacity than needed would not be able to keep up with the current load if you had a lot of accessories on so the battery would discharge. The warning lights would tell you something is not right. If the current load stays within the alternator's capability you wouldn't notice a problem.

#5 kmix99

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Posted 23 July 2005 - 12:45 PM

There are a lot of very poor quality remanufactured alternators being sold out there. A lot of the people rebuilding them get minimum wage and hate their jobs, rebuilding hundreds every week. Not all of the internal components are replaced with new ones. I have had several encounters with faulty rebuilds--- for that reason, I always buy new or have my old one rebuilt locally.

If you think/test your new alternator is ok, then I would do as the others have suggested and reset the ecu.

#6 Mark-O-Back

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Posted 23 July 2005 - 11:05 PM

Hi Sweden, The ac cycling on / off might be the defroster. Try pushing the heater control button releasing the defrost. The defrost with the orange icon will run the AC.
Good luck,
Mark

#7 Sweden

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Posted 23 July 2005 - 11:41 PM

I'll check out the defrost to see if something is fishy there. If resetting/reprogramming the ECU involves only disconnecting the negative battery post for 45 minutes and then driving the car again, it had no impact. I receive no warning lights on the dash; the charging part seems completely normal. It is the strange idle, A/C, etc. that is not right. If the alternator was rebuild in Sweden, I would suspect that it was rebuilt adequately. There isn't usually a problem with quality here (and one pays for it!).

I'll bring the vehicle to the electric shop that sold me the alternator tomorrow. He'll test it. Is there anything he should look for, or any certain readings that he should receive with this vehicle (output levels, etc)? I'm rather clueless n this front.

Thanks again!

Sweden

#8 Cougar

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Posted 24 July 2005 - 01:14 AM

I don't think there is a problem with the alternator though a load test on it will show you the capacity it has.

The alternator has nothing to do with the AC turning on and off.

#9 Setright

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Posted 24 July 2005 - 05:51 AM

Hejsan!

The wrong type of alternator will give you some weird problems. Are any of the dashboard warning lights glowing dimly? Does the charge wire that attaches to the alternator fit well? Did the cable need to be stretched to reach?

Have you measured the charge voltage?

#10 Sweden

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Posted 24 July 2005 - 01:58 PM

No problems with stretching wires or dim dash lights. The alternator fit on nicely; although the guy that did sell it to me said that it wasn't an exact match. I will meet with him first thing in the morning (in Malmo). He'll measure voltage.

Are Subaru's less problematic to find parts for in Denmark; maybe I should relocate and commute. Oh ya...real estate prices are a big hindrance...!

Sweden

#11 Setright

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Posted 25 July 2005 - 01:47 AM

The present traffic is the other way across the sound. Danes are moving to Malmoe and commuting for work in Copenhagen.

And NO, parts aren't easier over here. Subaru didn't have a distributor in DK until a year ago, after a three break, during which we sourced parts from Sweden!

I had a mis-matched alternator installed on a Legacy once, it did some odd things. Get the mech to find you the correct one. Mine was a rebuilt job, that cost around 1200 DK kr.

#12 Sweden

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Posted 25 July 2005 - 01:59 AM

I paid 3300 SEK for mine, so you did o.k. actually. We'll check it out this morning. Even if one buys an alternator from Subaru in the U.S. these days, one will get a rebuilt one. That is all that is avalable on the market.

Yes, there are loads of your kind heading over the bridge to buy property here. That's o.k. by me, because we bought a house last year (in Eslov). Let the real estate prices rise!

Sweden

#13 Sweden

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Posted 25 July 2005 - 09:24 AM

Went to the electric shop. Alternator seems to check out. His suggestion was the Subaru repair shop here in the area. The problem is that this is Sweden so the guy is on vacation 'til Aug 15...

Question: Are there different alternaotrs to different models? For example will a 96 Legacy have a different alternator than an 96 Legacy Outback?

I noticed that the rpms fluctuate about 200-300 at idle when the car is doing it. Could this be totally unrelated to the alternator? What else may cause it?

Sweden

#14 Cougar

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Posted 25 July 2005 - 01:28 PM

You mentioned in your first post that the AC was turning on intermittantly, is that coinciding with the RPM fluctuations? There are some things that can make the idle of the engine change to keep the charging up. The AC is one of them. I still don't understand why the AC is turning on if you have the system off, unless the defroster is on.

#15 Setright

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Posted 26 July 2005 - 12:37 AM

I think it may be time to start looking around the alternator. Maybe something else was disturbed during the install? Any wires pulled out? Hoses disconnected?

#16 bgd73

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Posted 26 July 2005 - 08:45 AM

Give it time to run run run! To compare it to changing a "power supply" on a pc, it gives a micro trauma if the original was bad, it got used to it, now it is good, must do the same. I learned this not to be a coincidence, after my 3rd alternator in 3 different model cars (including GM), It took a few ecm resets and stops, starts, and run run run the engine! The more precise
they get, the more stubborn it seems.... give your trouble time.

#17 Sweden

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Posted 26 July 2005 - 02:58 PM

There is something there, I feel, more than giving it a bit of time. Something is up... Cougar, you mentioned the A/C again. Yes, if drives as though the A/C keeps coming on. I feel it when I drive. I also notice that there is a puddle of H2O under the car (under the appropriate waste pipe by the firewall) when the car sits without the A/C ever being on. Is that o.k.?
The sequence seems to be some sort of A/C pump movement, fluctuated idle (200 RPMs), and then normal steady idle.

Thanks again for all the responses!

Sweden

#18 Cougar

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Posted 26 July 2005 - 05:57 PM

I doubt the problem is going to just go away after time. You could just pull the power connection to the AC compressor and see what happens then. The dripping water seems to say the AC is working even if you don't have it on. Pulling the power connection to the compressor will stop that from happening. If the compressor is coming on when it shouldn't, then you need to find out what is causing this to happen. Perhaps the switch is flakey.

#19 Sweden

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Posted 02 August 2005 - 03:05 AM

I have had the opportunity to analyze the problem a bit better now. I started the car and let it run for about 15 minutes. There is still the rough or changing idle, but it is less frequent with the defrost off (& A/C pump off?). It runs nicely for say 45 seconds and then starts idling unevenly for about 5-15 seconds, with the alternator making some what could be discribed as a rotation noise. I am wondering if I bumped something when I installed the new (rebuilt) alternator, if it is still the incorrect alternator (no lights on the dash and it checks out according to the shop), or if it is only coincidental that I noticed this 'problem' after I installed the alternator.

It seems as though 'Midwst' has the same issues here...

Also, I noticed now that my windshield is leaking through the top of the gasket onto the mirror etc. (it was replaced 1-1/2 years back); should I take it back tot he shop that replaced it or try to fix it myself? The neighbor stated that normal silicone dowsn't do the trick because it doesn't stick so well to automotive paint.


Sweden

#20 brus brother

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Posted 02 August 2005 - 10:56 AM

DEFROSTER IS ON or OFF???
You will get that same puddle of water simply from running the defroster as when you run the AC. Not sure but it would probably give you the same fluctuations as when the AC compressor cuts in and out since it uses the same compressor. Turn off the defroster!!

#21 frag

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Posted 02 August 2005 - 11:06 AM

Like I wrote in another thread where you mention your temp gauge being pegged at C, the coolant temp sensor which control via the ECU both the fuel trim and temp gauge is a likely culprit. If it has never been replaced, I would replace it since it's not very costly. If you ever had problem starting when the car's engine is hot, then the coolant sensor is almost certainly at fault.

#22 Sweden

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Posted 02 August 2005 - 03:09 PM

Unfortunately the coolant sensor has been pegged at C for the past 2-3 years. I'm not sure if I should admit that though...
No problems with starting the vehicle hot or cold. I replaced one of the sensors when the problem first started to no avail. Where is the one for the gauge located? The thermostat as well. I need to come up with another sensor, but that could be a pain here in Sweden.

Yes, I did turn off the defroster. It made the problem less drastic, but it still unfortunately persists.

Sweden

#23 frag

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Posted 02 August 2005 - 03:19 PM

Unfortunately the coolant sensor has been pegged at C for the past 2-3 years. I'm not sure if I should admit that though...
No problems with starting the vehicle hot or cold. I replaced one of the sensors when the problem first started to no avail. Where is the one for the gauge located? The thermostat as well. I need to come up with another sensor, but that could be a pain here in Sweden.

Yes, I did turn off the defroster. It made the problem less drastic, but it still unfortunately persists.

Sweden


There is only one sensor on your car. It sends its info to the ECU which in turn uses it to trim fuel, start the rad fans and control the temp gauge. That's why I think a non working temp gauge could be a sign there is a problem with that sensor or with its connexions which would cause also a fuel trim problem. It seems like a possibility to explore.

#24 Sweden

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Posted 03 August 2005 - 02:27 AM

I'll order one from the states and have a family member sent it over. It is the cheapest and most efficient way...
But, I was just reading another thread about alternators. I have slight dimming of head lamps, dash lamps, etc. with the fluctuations (while I am driving), and I just replaced the alternator. I feel for some reason there is a connection, or is the alternator just not keeping up?


Sweden

#25 Cougar

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Posted 03 August 2005 - 03:37 PM

I would check the voltage at the sensor to see what it is. Also remove the connector to the sensor and measure the resistance of it. You need to see if the problem is due to a bad sensor or the connection to it. The resistance of the sensor should change with the temperature. The resistance should may go down as the temps go higher. I'm not sure which way they go right now. The main thing is that the sensor lead(s) should not be grounded or shorted.




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