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Hi All, Thanks for hosting this forum. I need help.
2002 KIA Spectra 4 door 50,634 Miles. 1.8L I4 DOHC 16V
There is some kind of electrical problem with my engine which makes a whining sound on the AM radio. The frequency is proportionate to the engine RPM's. It's like radio frequency interferance (RFI)
I thought it might have been a bad plug wire so I did a tune up (new plugs & wires) but it is still there. No loss, it needed a tune up anyway.
The battery is charging just fine and there is no noticable loss of power on the engine.
Anybody have any clues as to what might be wrong?
I don't know if it is related, but there is a whining sound under the hood for the first 5 minutes of operation in the morning. It sounds kind of like a power steering pump or something like that. It is also proportional to engine speed.
Thanks in advance, Jim (okrobie)
P.S. I have an OBD2 setup but haven't tried it yet. Would this help?
It sounds like power supply noise which also changes as the alternator RPM's change.
There's a number of ways to sort out this power supply noise.
1) Check that the grounding connections are good on the engine-chassis, battery-shassis, and battery terminals a good and clean.
2) Most alternators have a noise suppression capacitor attached to the alternator main terminal - check that this is there.
3) A bad battery could also contribute to the noise problem.
4) You could get a small LC filter (Inductive/Capacitor) and connect this in the radio power supply wire close to the radio - most radio supply shops have these and they're cheap and simple to fit.
The OBD2 will not help diagnose this one, although it could confirm that the voltage is correct.
Hey Ron, All the grounds look good, but the battery is not taking a charge. The alternator is putting out 14.55 volts but the battery is only holding 12.5. More to follow...
Hmmm... Wal-Mart load tested my battery and they say it is good, not even needing a charge. I'm sure it should charge higher than 12.5. Am I correct?
I am measuring voltages from the battery terminals, the lugs, and from alternator to engine block, and alternator to frame.
I get 14.55 in all cases from the alternator and only 12.5 from the battery. The battery shows 13.2 Volts when I first shut off the engine but within a minute, it drains down to 12.5.
Are these readings normal???
One other symptom I didn't mention is that yesterday for no reason the radio presets died. The clock didn't reset though.
There are no loose connections anywhere that I can find. If I wasn't reading full alternator voltage to the block and frame I would re-do all of the ground connections.
Maybe that's my next alternative anyway, but I'm still suspicious of the battery.
What do you think Ron (and/or any others out there)
Thanks again, Jim
P.S. I just got out my load tester and it reads Condition "Good" and Charge "50%" My Digital Volt meter reads 12.6 Volts This seems to confirm my theory of battery not holding charge, dispite what the battery babe at Wal-Mart said. What do you think???
a car battery is only ment to hold a charge of around 13 volts and your problem sounds like it could be in the wiring if i was trying to solve the problem i would run a wire from the battery to your radio with a fused link and use that for power
Thanks elak, I appreciate the limit on the maximum charge voltage, but I was thinking 12.5 is lower than normal.
Maybe I'll just have to re-do all of the ground connections.
I'm not so worried about the radio except that it seems to be an indicator of a deeper problem. The radio noise has been getting gradually worse in the last few days, but I'm sure it will go away on it's own when this problem is resolved. Maybe I'll just have to wait a few more days 'till something really breaks or burns up. :-)
I'm not sure, but I think the alternator is good based on the measured output voltage. I don't know how to tell if I have a bad diode, but I'm sure if it was going bad, it wouldn't put out 14.55 V.
Is there a voltage regulator in the loop? Perhaps that's worth looking at. Maybe 14.55 it higher than the chargong voltage should be.
Thanks elak, I appreciate the limit on the maximum charge voltage, but I was thinking 12.5 is lower than normal.
Maybe I'll just have to re-do all of the ground connections.
I'm not so worried about the radio except that it seems to be an indicator of a deeper problem. The radio noise has been getting gradually worse in the last few days, but I'm sure it will go away on it's own when this problem is resolved. Maybe I'll just have to wait a few more days 'till something really breaks or burns up. :-)
I'm not sure, but I think the alternator is good based on the measured output voltage. I don't know how to tell if I have a bad diode, but I'm sure if it was going bad, it wouldn't put out 14.55 V.
Is there a voltage regulator in the loop? Perhaps that's worth looking at. Maybe 14.55 it higher than the chargong voltage should be.
Anyway... Thanks for the input. Jim
The charging voltage at the battery should be what you measuring, and the battery voltage of 12.5 v is also normal when not charging.
You should measure the same voltage from anywhere on the shassis to Bat+ and engine to Bat+, if not the same then you do have a grounding problem.
You could possibly detect a bad diode by selecting you multimeter to AC volts and see what you get with the engine running - it should be zero Vac , but a bad diode would generate some ac.
The voltage regulator is built into the alternator.
Thanks Ron, It's raining so I won't be able to continue today. My shade tree gets verry drippy for some reason.
I measured the voltages with the engine running and got full voltage (14.55 VDC) From the Positive battery terminal to the engine block and to the chassis. I'll try it with the alternator off next.
I should have guessed the technique for diagnosing diode shorting in the alternator.
I just know in my gut that you are right about it being a power supply issue. Now all I have to do is track it down.
Engine makes whining sound on radio HELP!
Linear Mode
