I have a 96 850 turbo that seems to have an elec problem. Car seems a little rough when its started. I noticed that my abs/tracs light (I know about this prob) dim when I push the gas while car is parked. Lights come back full on when I let gas go. This happens only at idle when I rev the car slightly btwn 800 and 1200 rpms. I had bat and alt ckd at Checker and Autozone and tests came back good although the guy frm Checker said it could be voltage regulator. Said he could only chk the regulator on the bench and not on the car. The car stumbles ever so slightly when I rev it like this but she drives like a champ otherwise! I put a scanner on it and nothing. She drives normally and I only exp this prob while parked. Volt meter at the bat says 14v and when i slightly rev it, drops down to 13v. Seems normal but the car stumbles a bit and lights dim. If I rev it higher, no stumling. I have changed plugs, wires, cap and rotor. I bought the car 4 mths ago and everything looks stock. Have not chngd the bat or alternator. Wires and posts are clean and tight. Just want to see if anyone has any other advice. I'm suspecting the regulator or bat and should probably replace them both but I'm on a budget right now. Its got to be one or the other. Thanks for any info!

edit: could this be a case of bad gas? I was reading another thrd and the guy described something similar to my problem.

 

bad gas wouldn't cause an electrical prop

i am leaning towards the voltage regulator as a possible source of your problem

-Mike

 

Check the Voltage at the battery again with the car running.
The probe the wire before the battery terminal and let me know what the reading is.

14v is pretty close from what I have seen lately it is a little high but still within range.

Also check all the grounds.

 

Greetings from Chicagoland.

If you could provide more info, it would be helpful (brands of the battery & alt, when they were replaced, etc...).

I had a similar trouble in summer, except mine was more obvious. At idle all lights were dim, but above idle the lights became much brighter and the heater fan ran faster too. It was a faulty voltage regulator on a rebuilt alternator that was OEM (Bosch) and had only 3 weeks or so. I was lucky that I didn't damage ECU's.

Also, I noticed that the ECU on 850 (BTW my car is 1994 Turbo T5 sedan) needs a few minutes to re-learn idle. When I did the timing belt, the car did not run right. Lights kept dimming & brightening, erratic idle, etc... What I did wrong was that after re-connecting the battery, I immediately turned the parking lights on (the first detent of the headlight switch). This seemed to have screwed up the idle. So, I disconnected the battery, waited for 10 minutes for the ECU relays to turn off, re-connected the battery and let the engine idle, only this time with all electrical loads off. After letting it idle for about 10 minutes, the problem was gone. I am not sure what the specified idle re-learning period is, but it worked in this particular case.

I've posted quite a few notes on the battery in the past. In case if you haven't read it, here's it:

Before testing the battery, make sure that the electrolyte (acidic liquid in the battery) is at the normal level (must be covering the top of the plates). When you do this, eye-protection is a must. I've seen some people acting macho, and had almost spilled the acid in their eyes. I wouldn't risk my vision for mere $5 and 3 seconds wearing it. In case if it gets in your eyes, though, milk seems to be a good solution.

If the electrolyte is at normal level, here are the tests (you might have done them already):

1. Voltage test w/DMM (Digital Multi Meter)
2. Specific Gravity test
3. Load test

1. The voltage should be at least 12.3V or higher (should be less than 13V). With the engine running, it could be 13-14 plus volts (mine reads slightly above 14V).

2. The S.G should reveal each cell's state of charge, unless you have a maintenance-free type. If you don't have one, an S.G tester is a cheap & good tool to have in your toolbox. S.G test usually reveals the condition of the battery.

3. If above tests show good and if the battery is still suspicious, load testing is the last resort. This requires diagnostic equipment but is the most accurate method of testing a battery.

A battery's life is somewhere between 3 to 5 years, depending on the brands & CCA rating. Battery with higher CCA seems to have somewhat less life.

850's seem to have very sensitive electrical/electronic systems and a good combination of battery + alt are a must. Should you decide to get a new battery/alt, I wouldn't buy cheapo as they fail prematurely. A good battery usually costs $80-$100. I have an Interstate Battery, they always served me very well.

Here's a book that I recommend FYI:

How To Diagnose and Repair Automotive Electrical Systems by Tracy Martin

http://www.amazon.com/Diagnose-Autom...970302-6868616

In general, books on electrical systems are full of nonsensical theories that hardly apply to actual hands-on procedures. This book seems to be the closest in practicality, though it does waste the first couple of chapters on theories. It may be helpful to you, but if someone knows better books, I would love to know about them.

P.S: for experts: Correct me if I'm wrong in some of my info.

I wish you luck finding the problem.

Regards,


JPN

 

Thanks! I'll try everything. The problem did come up when I was replacing the upper motor mount/support and I removed the battery. I left the bat off for the night. The Volvo tech I spoke to said the relearn period is 500 miles. I'll try and unplug the bat and reset the ecu tonight. I'll let y'all know what happens. If not, that alt is coming out and getting bench tested.

[IMG]local://upfiles/7773/0769D8AB162E46A18E09197036CCBC77.jpg[/IMG]

 

I reset the ecu and prob still was present so I took out the alt and had it tested. Came out good but decided to replace anyways after reading other threads. I also replaced the battery and the problem went away. Thanks for all the info!

 

Hello Mr. Coldwell850,

Glad the problem has been solved, a good way to start the New Year!

You can actually test the voltage reg by connecting a digital multimeter across the battery and revving the engine up to about 2,000 RPM. The voltage may rise a little bitaccording tothe given RPM, but it should stay at the specified range, even revving the engine to the red line. My first replacement alt (surprisingly, a rebuilt Bosch) kept producing more voltage until I turned the engine off when I saw 17V (the 2nd replacement I got under lifetime warranty has been working well so far). But in order to test individual diodes in the voltage reg, yes the alt has to come out and bench tested.

I've heard too many horror stories about batteries. I am curious as to what brand batteries other people use, I've always liked Interstate Batteries. You definitely get what you pay for when it comes to auto parts (and many other products alike).

Happy New Year,


JPN