George Z. Posted May 23, 2009 Share Posted May 23, 2009 I have a 1997 LS400 and I've had a problem whenever I drive the vehicle for more than approximately 45minutes to 1 hour, the A/C blower motor weakens and doesn't blow through the car's vents "accordingly." What I mean is that when it's on "level 3" (out of a high of 5), it barely feels like a "level 1" (and when it's on "level 5" it'll barely feel as if it's on "level 2"). When this happens, the air coming out (albeit it's a lot less) is still cold and it NEVER gets hot...just the speed and strength of the blower motors WEAKENS. When the car is turned off for a little while (between 30 minutes and 1 hour), and then restarted, the problem goes away and the A/C system functions perfectly with normal fan speed and strength accordingly. That being said, I had the alternator checked today and when the A/C is on "Level 1", the alternator is putting out full charging strength. However, if the A/C fan is put on any level between 2-5, the charging is very weak (barely at 12). I went ahead and replaced the alternator as it was determined to have gone bad, and I replaced it with a new alternator. The problem still remained!!! Nothing changed. Now, with all this being said, my "battery light" in the dash (the one to let you know the charging is on the WEAK side) has NEVER come on. Nor has the car stalled or done anything out of the ordinary. My overhead map light did flicker last night when I drove the car, but neither the headlights nor any other lights have been flickering in the vehicle. I was told this could possibly be an A/C blower motor "resistor" that's going "faulty" and when the fan speed is higher than level 1, it's pulling too much current from the charging system, hence draining the alternator and showing the charging level to be on the low side. Does anybody have any experience with this similar problem in the past? Any help? Please either reply or call me (713-459-6411) as I'm needing to fix this by tomorrow (Saturday 5/23/09) withOUT taking it to the dealership. Any help you may be able to offer or throw my way is greatly appreciated !!!!! Quote Link to comment Share on other sites More sharing options...
curiousB Posted May 23, 2009 Share Posted May 23, 2009 Do you have a DVM (digital voltmeter)? They are only $10-20 for cheaper one and very handy. You could measure battery voltage at the battery terminals. Check it with car off should be around 12 VDC with car running but least amount of items turned on should be around 13.3 VDC then running with everything you can turn on turned on (high beams, blower motors, rear defog, audio, ...) should stay at around 13.3VDC If you have an alternator probelm you'll see the voltage drop with all these other electrical loads as well. The alternator doesn't know who is pulling the load. If you find only the blower motor pulls the battery down but nothing else then your theory is a possibility. I doubt it though. If it were faulty and pulling excess load then the fuse would pop (unless someone put in a higher value fuse than recommended). If you have an alternator problem then the cumulative load of all these items is far higher than just a blower motor and it should be obvious in the reading (and maybe in a dimming of the headlights). I would rething you alternater testing more in line with above and also make sure the belt to the alternator isn't slipping when the electrical loads are high. Quote Link to comment Share on other sites More sharing options...
George Z. Posted May 24, 2009 Author Share Posted May 24, 2009 I tested the car's charging & battery with a volt meter and with the car off, it's right around 12 volts. With the A/C fan level on level 1, the charging is in the high 13's and almost 14 volts. However, with the A/C fan level on level's 2-5, the charging system is back down to around 12 volts. The interesting thing here is the fact that I can turn the A/C off, but turn ON the headlights, radio, wipers, dome lights, etc...and the charging is perfectly fine at around 14 volts or a hair-shy of 14 volts. I have done the following today: The cabin air filter has been changed. The one it had in the car was terribly worn out and filthy. The problem has not gone away though. I am going to try to install a used blower resistor / relay from a local junkyard. I will then run the car for more than an hour on a high level on the fan motor of the A/C and see if the problem will get taken care of. Also, I have replaced the serpentine belt with a brand new Gates belt from O'Reilly. The belt that came out of the car looks like new, so I am now starting to think whether or not the accessory belt tensioner (which is "spring-loaded") could possibly be allowing the belt to "slip" over all the pulleys...? I should have an update for us all by this coming Monday. Thanks again for your replies and helpful advice!!! Let's keep this wonderful forum site going strong... Do you have a DVM (digital voltmeter)? They are only $10-20 for cheaper one and very handy. You could measure battery voltage at the battery terminals. Check it with car off should be around 12 VDC with car running but least amount of items turned on should be around 13.3 VDC then running with everything you can turn on turned on (high beams, blower motors, rear defog, audio, ...) should stay at around 13.3VDC If you have an alternator probelm you'll see the voltage drop with all these other electrical loads as well. The alternator doesn't know who is pulling the load. If you find only the blower motor pulls the battery down but nothing else then your theory is a possibility. I doubt it though. If it were faulty and pulling excess load then the fuse would pop (unless someone put in a higher value fuse than recommended). If you have an alternator problem then the cumulative load of all these items is far higher than just a blower motor and it should be obvious in the reading (and maybe in a dimming of the headlights). I would rething you alternater testing more in line with above and also make sure the belt to the alternator isn't slipping when the electrical loads are high. Quote Link to comment Share on other sites More sharing options...
curiousB Posted May 25, 2009 Share Posted May 25, 2009 Sounds like a faulty blower motor to me. The resistors are just used in series with the motor to slow it down for the lower speed settings. High setting bypasses all resistors. If the high setting is pulling down the battery then maybe motor bearings are starting to seize putting a lot of extra drag on the motor (or could blower wheel be dragging on blower body?). The surprising thing is the blower fuse should be popping here as the current must be quite high to drag the battery down. The other scenario is the alternator isn't cutting it due to worn brushes, loose belt, and/or faulty voltage regulator. The puzzling thing is high beam headlights plus rear window defogger should draw more than the blower motor so if its the charging system then this load should pull down battery as well. Its important for this test you measure battery at the battery terminals (both + and -) and not just any 12VDC spot you can find. This way you eliminate voltage drops in the car wiring which might vary over different loads and steer you in the wrong direction. Before buying resistors I'd be sure to rerun the tests again measuring voltage at the battery in an A vs B test. Where A is blower at high speed (nothing else on) and B is no blower but high beam headlights on and rear window defogger on. Both of these tests with engine running. If battery voltage is dragged down more with blower then I'd suspect blower motor. The blower motor should be getting quite hot though if it is pulling down a good alternator set up. Might want to double check blower fuse to be sure someone didn't "fix" this in the past by putting a too high value fuse in the slot (explaining why fuse isn't popping) and see if you can get to the blower motor case after its been running 5-10 minutes to see if it is hot to the touch (careful if its faulty it could be very hot (ie burn you)). If its worn bearing might be able to recover with a clean and lube. otherwise a new blower motor is the way to go. Oh just reread your post. Dop this test with heat not A/C. A/C introduces the possibility of a faulty compressor clutch drawing too much current. Need to isolate to the fan motor vs everything else to be sure Quote Link to comment Share on other sites More sharing options...
curiousB Posted May 25, 2009 Share Posted May 25, 2009 Another possibility is the is evaporator coil is icing up and restricting airflow. This occurs when refrigerant is low. Could explain why the system recovers as the iced up coil melts. Might want to have the A/C charge checked. Quote Link to comment Share on other sites More sharing options...
Lucky13 Posted May 26, 2009 Share Posted May 26, 2009 Does sound like your 'frigerant may be low. Quote Link to comment Share on other sites More sharing options...
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