Whining noise from Crown Vic

Not open for further replies.
Jun 23, 2010
My '09 Crown Vic with the police package (78k miles; 2100 idle hours) started making a whining noise last week. It speeds up and slows down with the engine rpms. Here are the symptoms that it has been making:

1. My electric fan will turn on right after I start the engine cold. It usually only engages when I turn on the A/C, which I have not been using.

2. It feels like the A/C compressor is engaging even when the HVAC selector knob is in the "off" position.

3. I took the car in to my mechanic and he couldn't find anything wrong with the A/C compressor at all. (I thought the compressor was making the whining noise)

4. Yesterday when I tried to start the car after work, it would not turn over. I was able to jump the car without issue. The battery was replaced in April of 2013.

So, does it sound like it is the alternator? It is hard to pinpoint where the whine is coming from, but the alternator is the likely suspect in my mind.
Sounds like a good place to start considering the no-start condition. Easy to replace.
Try turning the pulley by hand to see if it's rough or if it makes a little noise.
You can easily disconnect the compressor or one of its pressure switches on the shiny AC tubes to kill it for winter. I think there's something messed up in your climate control head that's demanding AC all the time, and the added load of the fan is making your alt whine. You could also pull your fan maxi-fuse for diagnostic purposes.
tensioner may be weak and making that noise. see if you can spin the belt by hand..just tugging in either direction. could be a idler bearing as well.

just because the battery is 2013 doesnt mean its good. Need to have it tested/load tested etc. to determine that.

alternator- the old test was the unhook the battery while running.. to test alternator pass/fail. but you can remove and have it tested also..or hook up a multimeter to the battery while running to see input.

fans on while cold.. is defrost on? i think defrost has to engage ac compressor in newer cars. rule out defrost for fans.
Originally Posted By: Roadkingnc
Take the belt off and see which idler pulley has a bad bearing.

As other mentioned, the A/C compressor will run if the defroster is on, and when the compressor is commanded on, so is the fan.
Get a long screw driver and put the handle end to your ear and the other to the running alternator. The noise or lack of it will determine if the alternator is the problem. I also agree with those who said the AC is messed up so unplug it.
What Eddie and 01rangerxl said. Grab a long screwdriver and listen for the problem. Alternator bearings whine (common), once in awhile an idler/tensioner will whine (but usually more of a grinding noise).

AC compressor should be off if the climate control switch is off. Compressor will run in A/C and defrost mode, and sometimes...possibly, whenever the control head thinks it should run. No idea what the programming is on that year climate systems. Turn climate control off and look at the front of the AC compressor and see if it is turning, not hard to do.
When I unplugged my alternator (while running) it whined and moaned really loud. Check yer plugs, could need a new pigtail?

89 Lincoln TC Signature here

GM has their alternator seizures/fires, Ford has the moaning alternator/PS pumps. I'd take the latter LOL
If the A/C compressor is constantly running, even with the switch off, check the A/C compressor relay in the fuse block under the hood. In our shop we have noticed that on some P71's the relay welds itself closed. Pull it and see if it stops the fan. Also, if the A/C compressor is not engaged, it could be the module on the back of the cooling fan motor unit.

The whining noise could be the Alternator, Idler, or tensioner pulley.

The P71's have a short battery life. A year is about average. Have the battery tested to see if it has a bad cell.

Hope this helps,
Update: I want to thank everyone who contributed their insight; I greatly appreciate it.

It turned out to be the A/C clutch relay, it was causing both the whining noise and the drained battery.

Thanks again for everyone who offered insight into my P71's issue.
Glad you figured it out and it was something simple.

The A/C compressor relay went bad in my truck a while back. At first when I would turn the A/C on I got nothing. Then after 10 minutes or so (next to the running engine - heat source) it would suddenly engage and seem to stay on constantly. When I replaced the relay, it started working fine again. I got the relay for $15 at a local Ford dealer...it was actually more expensive to get a BWD relay from Advance.
Originally Posted By: Miller88
This may change my mind against using junkyard relays ...

Yes, my mechanic told me that when the relay was remaining on after I turned the car off, it was pulling 3 amps. At that rate it would drain a good battery in about 2-4 hours.
Originally Posted By: eljefino
You can easily disconnect the compressor or one of its pressure switches on the shiny AC tubes to kill it for winter....

The compressor is in fact needed for the winter. Try defogging a windshield when it's raining/snowing without it. The a/c compressor dries the air out, thus aiding in the defogging process.

The right thing to do is fix what's wrong, not start pulling fuses/plugs.
I have defogged many windshields without an A/C compressor. It doesn't run (or runs very little) when it gets cold.
Almost any reasonably newer car uses the compressor even in the coldest weather. It may cycle off during heating but on some vehicles it never stops unless the pressure switch tells it to...
Not open for further replies.