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Car Forum / Honda Cars / November 2004Flashy Battery and heater lights on dash
I got two lights that keep flickering at low rpms and go off at higher rpms (2500 or so) was intermittent now is doing it most of the time, the lights stay on below 2000 and flicker up to 2500 or so then go off after that its the battery light and the light that looks like a radiator or catylitic converter with heat wiggles above. 85 honda integra, 1600 dohc injected 5 spd. >I got two lights that keep flickering at low rpms and go off at higher rpms >(2500 or so) [quoted text clipped - 3 lines] > catylitic converter with heat wiggles above. > 85 honda integra, 1600 dohc injected 5 spd. It sure sounds like a bad alternator to me. Getting the alternator out probably takes an act of God, so you want to diagnose it first if possible. If you have access to a digital voltmeter, measure the AC voltage across the battery with the engine running. It should be below 0.1 VAC, usually below 0.05 VAC. Readings of 0.5 VAC or more are a strong indication of a bad diode (or several) in the alternator. That would be consistent with the flickering battery light. Mike > I got two lights that keep flickering at low rpms and go off at higher > rpms (2500 or so) [quoted text clipped - 3 lines] > catylitic converter with heat wiggles above. > 85 honda integra, 1600 dohc injected 5 spd. Sometimes car makers do funny things like tying warning lamps together with diodes in order to implement lamp test. My guess is that your coolant temperature alarm is tied to the alternator warning light so that if the latter comes on, the former comes on too (but not vice versa). This is done so that you have a chance to check that the temperature warning light bulb is good. So, my guess is that there is no problem with the cooling system. Alternator light flickering or staying on at low RPM is a typical symptom of a bad alternator. It could be a case of bad diodes as "Michael Pardee" suggested and his test is easy enough to do. I if the alternator is original to the car it is more likely to be worn out brushes. They are replaceable, but I don't know how easy it is to get access with the alternator still in the car. The nominal output voltage from the alternator is 14.5 V for every Honda I have checked (back to 1987), your Integra is probably the same. Start the engine and turn on your headlights. Then measure the voltage at the battery. Slowly increase the RPM to about 3000. As you raise the RPM, the voltage should stabilize at 14.5 V +/- 0.6 V. With a good alternator the voltage should stabilize at 14.5V +/- 0.6 V at or just above idle. In your case the voltage probably reaches 14.5 V at around 2000 - 2500 RPM. If so, alternator is bad. A bad battery can also make the alternator light come on. Also, a bad battery will wear out your alternator quickly. If your battery is more than 4 years old, I would replace it just as a matter of course. It can sometimes be hard to find out if the battery or the alternator is at fault; A bad battery can be a huge load and drag down the voltage from the alternator, particularly at low RPM. Conversely, a failing alternator will not charge the battery properly, reducing the voltage. If you measure the battery voltage before starting the car (after it has not been used for at least several hours) you should see at least 12.6 V, If you do, then the battery is not causing your alternator light to come on. If you see less than 10.5V, then the battery is most likely bad. Inbetween? most likely a problem with the alternator. >>I got two lights that keep flickering at low rpms and go off at higher >>rpms (2500 or so) [quoted text clipped - 39 lines] > come on. If you see less than 10.5V, then the battery is most likely > bad. Inbetween? most likely a problem with the alternator. Ok done the check, 1200rpm the voltage across the battery is 15V. I put the setting on 200 ACV and the readout at 1200rpm was 30.0? is that right? or was i supposed to do something else? <snip> > > Alternator light flickering or staying on at low RPM is a typical > > symptom of a bad alternator. It could be a case of bad diodes as [quoted text clipped - 10 lines] > > voltage probably reaches 14.5 V at around 2000 - 2500 RPM. If so, > > alternator is bad. <snip> > Ok done the check, 1200rpm the voltage across the battery is 15V. I put > the setting on 200 ACV and the readout at 1200rpm was 30.0? is that > right? or was i supposed to do something else? 15V is a bit high, but within spec. (In my experience, even though the spec is +/- 0.6V, the voltage is usually well within +/- 0.1V) With the instrument on DCV, what voltage do you measure at idle, at 1200 RPM, at 2400 RPM and at 3600 RPM? The reading of 30.0 on ACV is bizarre. Different meters behave differently on the AC setting (i.e. a precious few measure the true RMS voltage of the signal, most measure the RMS value of the AC component only), but regardless, 30.0 V is very high. Could it be that it was 30.0 mV? What type of instrument do you have? With the instrument set to DCV, what voltage do you read with the ignition off? >>>I got two lights that keep flickering at low rpms and go off at higher >>>rpms (2500 or so) [quoted text clipped - 43 lines] > the setting on 200 ACV and the readout at 1200rpm was 30.0? is that right? > or was i supposed to do something else? Oops... it sounds like your meter is like most analog meters - it just uses a rectifier with no blocking capacitor to measure AC. Those don't work for this test because of the DC voltage riding on the battery. Try another digital voltmeter if you can get your hands on one. Mike |
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