Ok, I have had this problem a couple of times before, generally when it is wet and cold outside and the result is a very dead battery.
The heat/ac blower fan continues to run after the truck has been shut off and the key removed. I believe that it even comes on after the truck has been shut off.
What could be causing this and has anyone else ever experience the same?
Check the blower motor relay in the under dash fuse box. If you have a windshield leak, this fuse box gets wet, and it could cause relays to close when they shouldn't. The blower motor is fed through its' relay from a fuse that is hot all the time, so if the relay closed when it shouldn't, the blower will run. When the blower is running, start pulling relays until the blower stops. Leave that one out at night, and see if your problem disappears. If the fuse box is wet, you have to get that windshield fixed, or everything in that fuse box will start to go nuts.
By the way my truck is a 99 F350 Crew, since I left that out of the first post. There is no relay for the blower motor in the under dash box. According to my owners manual it is under the hood. As I said this problem seems to be associated with cold and wet. I also have other "electrical gremlins" in this truck and my guess is these all may be related to the water issueand that would make even more sense with the power disribution box. I have had the ABS light come on then just go off after a couple of start ups and the same with the air bag light. I really wonder if the box getting wet isn't a part of this. Unfortunately I have never been able to replicate the conditions when the strange things happen the only regular issue is the blower motor. I am going to replace the blower relay and see what that does.
Go figure power goes into the relay and out to the blower motor. There is no other way to keep the blower motor on unless its getting power there. Unless someone put an accessory on the truck and hooked it up incorrectly or two wires melted together.
Question's do you have all blower speeds when it stays on. If you turn the heater sw to off does it still stay on?
Yes, I do have speeds when it stays on and if I turn of the heater/ac switch to off it goes off. There are no real accessories on the truck except for the trailer brake control and a new radio (but it goes off).
The key sw powers the relay so you may have to measure the input to the relay to see if it goes out with key off. I'm guessing its not so that means that its either a key sw or back feeding from some other source.. Let me know if you need wiring help I can tell you where to measure.
If the blower relay stays closed with key out you need to check the output of the key switch with the relay out a test light from ground to term 85 of the relay socket P/O wire purple orange tracer. If this wire is hot with key off let me know.
Hi Dick, I have not had the problem for the last 2 days with the blower staying on.Go figure,when I want to fix it it dissappears. I will have to wait till it acts up again to test it the way you described. Thanks alot for all your help, Rich
hey guys I have a similar problem with my 2000 navigator but not only does the blower motor run but the running board lights come on and off the radio comes on and goes off and you can hear the chime come on and go off like the door is open. all this happens with the key out of the ignition. any idea what it is?
I'm resurrecting a 3 yr old thread - as I have identical problems but have not been able to resolve it. I've seen 5 or 6 threads on the subject, but have not identified a resolution. Here are the basics:
2001 F350 V10 Crew Cab 4wd. No mods except trailer brakes.
Despite age, only 35,000 miles. Cold, dry week. Blower works fine, but does not shut off when turning off ignition and removing key. If you turn the "service selector" switch to off (heat/AC/vent switch), then the blower shuts off .
1) With ignition off but blower fan running, if Relay #31 (Under hood, second from firewall) is pulled, blower stops
2) Swapped that relay with adjacent identical. However problem NOT solved (identical symptoms)
3) Replaced relay with other adjacent. Still did not solve problem. Could not tell if any of them “clicked” when reinserted, but fan restarted on all three relays.
4) Pulled fuse #22 in cab (10 amp blower motor relay coil). Did not shut off fan.
5) Also pulled fuse #23 in cab (air bag module in the event it was somehow back-powering). Did not shut off fan.
6) Unhooked battery for 5 min with light circuit on to drain. Did not remedy.
7) Pulled battery entirely from vehicle. Noted red eye (partially drained?). Put on charger overnight. Curious whether low amperage/voltage could cause the blower to not shut off entirely?
8) reinstalled battery. Lots of electrical clicking up under the "cubby hole". Didn't have all the panels off, but could grasp the electrical connection module and feel constant clicking prior to first start up. I hope it has something to do with the initialization of the computer! Also thought I heard something shift a few times up by the right headlight. [Note: truck has original battery, 8 yrs old, only 35k miles. Although I've never had any issue with low battery I may replace it regardless.] The OEM battery still tests good, engine starts great, headlights perfectly bright - no indication of battery issues, but I'll replace regardless.
9) Started truck, let it run for 15 minutes
10) I don't see anything wet or damp anywhere like leaking windshield discussed in some threads. Everything looks dry and pristine.
11) Nothing I've tried has remedied anything. Removing key still allows fan to run unless service selector (heat/AC/vent/) set to "Off"
12) No historical electrical problems - had electric brakes for 4 yrs with no issues. Only exception was the "door ajar" issue that was resolved with WD40 in the door latches. No history of damp/wet.
I'm headed to the airport in two hours for a 2 day trip. Hopefully truck will start for the trip home! If anyone has any ideas on troubleshooting, please post some suggestions and I'll attack them Saturday and report the outcome! I read some comments about measuring voltage on certain wires under the dash - but it wasn't immediately obvious what was requested, and I ran out of time to figure that out) Thanks in advance for any suggestions.
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