Power drain when using vent/heat fan October 26, 2008, 08:44:17 AM I've been battling this for awhile now. Whenever I turn on the heat, ac or vent and use the fan I get a hugh power drain. To give you an idea, nothing else will be on, no headlights, no stero, no wipers, etc. When I turn on the fan at low I get a power drop from 14.1 (from volt meter) to 13.0, I know this isn't much of a drop but, put it to medium and it drops from 13.0 to 12.2, put it on high and it drops to 11.7, this is while I am driving. Once at idle it stays at 11.1. Now turn the fan /heat off (competely) my power comes back to 14.1, I can run the headlights, fog lights, wipers, stereo (with 600 watt amp) and the volt meter stays at 14.1 running and 13.9 at idle. Why would there be such a hugh drop in power when using only the fan? I first thought that the AC compressor was coming on no matter where the switch was at, so I unplugged the compressor and still the same problem. Any help or advice would be greatly appreciated. Oh, on another note, I do have a power drain somewhere as if the car sits for a couple of days without being started the battery goes dead. I'm still looking for that one. Quote Selected
Power drain when using vent/heat fan Reply #1 – October 26, 2008, 10:08:21 AM two things........you may need to clean out the squirril cage on the fan. it may have on the blade making it heavyier.rig up a test light with a small low current light bulb such as the little bulbs found in your dash. unhook your pos battery terminalconnect one side of the light bulb to the pos bat post.connect the other side of the light bulb to the pos bat cable.rig up a block of wood to keep the door dome light switch closed.with no key in or nothing on, start pulling fuses one at at time.when the light bulb goes out, go to my sticky for the evtm and study the wiring.its always easier to start unhooking the output leads one at a time on the starter solenoid instead of fuses right off the bat.Unhooking ring lugs at the starter solenoid makes it easy to see which circuit and what feed wire is the problem area.dont forget to unhook stuff you have done aftermarket as well.if the light does not go out, its going to be an unfused circuit usually isolated to the start / charge / ignition circuits. Quote Selected
Power drain when using vent/heat fan Reply #2 – October 27, 2008, 07:26:52 AM Thanks for the info, will give that a shot this week. Quote Selected
Power drain when using vent/heat fan Reply #3 – October 27, 2008, 02:59:02 PM Have you had the battery and alternator checked? Quote Selected
Power drain when using vent/heat fan Reply #4 – October 27, 2008, 04:40:02 PM Your charging system isn't keeping up with the load of the motor(which is at approx 20A on Hi)... Since you are also having a discharge problem, I suspect the alt probably has a leaky diode... If you have the original 2G style alt, they are only approx 65A max and really don't charge well at low speeds... This was one of the changes for '88 when Ford went to a Hitachi alt on the TCs... The 3G alt upgrade is almost mandatory for the TCs, but beware, one member had a fire after making said swap... Don't try it unless you are good at electrical wiring... Quote Selected
Power drain when using vent/heat fan Reply #5 – October 28, 2008, 07:28:55 AM Quote from: vinnietbird;240565Have you had the battery and alternator checked?Yeah, I did, it's a new battery and alternator. Quote Selected
Power drain when using vent/heat fan Reply #6 – October 28, 2008, 07:31:30 AM Quote from: TurboCoupe50;240582Your charging system isn't keeping up with the load of the motor(which is at approx 20A on Hi)... Since you are also having a discharge problem, I suspect the alt probably has a leaky diode... If you have the original 2G style alt, they are only approx 65A max and really don't charge well at low speeds... This was one of the changes for '88 when Ford went to a Hitachi alt on the TCs... The 3G alt upgrade is almost mandatory for the TCs, but beware, one member had a fire after making said swap... Don't try it unless you are good at electrical wiring...I figured that was part of the problem and put a 150 amp alternator in the car, took care of the problem when running the stereo, lights, wipers, fog lights and I stay at a steady 14.1 charge when driving and 13.8 at idle. Turn all that off and turn on the fan and it drops. Quote Selected
Power drain when using vent/heat fan Reply #7 – October 28, 2008, 01:28:02 PM I'd guess there's some sort of short on the wires for your fan, or your fan motor is dead. Well,,, dying. Quote Selected
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