Can't turn off the H/A blower motor. It stays on constantly.


Asked by Oct 20, 2015 at 04:07 PM about the 2003 Mercury Grand Marquis LSE

Question type: Maintenance & Repair

We have replaced the blower motor resistor three times in the last three months and now the blower won't turn off again. Once it quit and it wouldn't turn on. Any ideas?

15 Answers


The blower resister will prevent the blower from starting however it's not used for stopping unless of course you remove it /// the motor will stop then for sure.(a little awkward) What was the original problem? If it was that the motor would not stop then changing the resistor was useless (as I said earlier it only allows the motor to run at a set speed) ... I'm only asking because I want to backtrack to the beginning. Did the motor run at all speeds before the problem occurred? When the motor does run now does it have all the speeds? Does the motor turn off when you remove the key? Answer these questions before I can go further

4 out of 4 people think this is helpful.

Say there Tom, on my car I went threw 7 resistors before my blower motor would work properly. That resistor will cause (in my case) the blower motor not turning off even with the key out of ignition, to not turning on at all, or just running on one speed. Parts store just kept warranting it and on each one I got looked the same as did my very last one but you could tell the company knew they had a problem with them because it was sealed differently. The question is does replacing the resistor fix the problem for a bit? Also I would recommend the OEM replacement. Also to help that resistor, my AC dryer vent was plugged not allowing the condensation to drain properly so it was ending up on my resistor. Something to check.

2 out of 2 people think this is helpful.

Thanks Tom and Rowefast! Everything was working great, then the fan motor quit. You could hear the AC functioning, but no air. The resistor was replaced and everything was great again, then the air wouldn't turn off. There was no change of speed when we tried. It does turn off when the key is removed - so far anyway. So we got another resistor and now the air blows on HIGH constantly. The parts store is replacing them, but the guy putting them on says it's a pain to get them in with his big hands. Ha! So, the resistor is working for a few days before going to one extreme or the other. Thanks to both of you again for your help.

1 out of 1 people think this is helpful.

OK .. but we are not done with you ,, yet (unless of course your done with us) Now that we have something to work on we can proceed. If thats ok then post OK ,,, There is good info we need to get together


Sure! Ha! I'm not through either since that air is blowing hard non-stop. I was wondering if there's a fuse that I could take out to just to make it stop for a while.


Hope this helps

3 out of 3 people think this is helpful.

Okay, thanks for the diagram. Judy


OK What do U need next??

1 out of 1 people think this is helpful.

I guess we'll just keep on replacing the resistors until one will work longer than a week. Don't know what else to do.


Are the resistors damp, wet, when you pull them out? Did you look at the dryer drain tube like I suggested? And what is the brand of resistor you keep putting in?

3 out of 3 people think this is helpful.

Try this~` turn the motor on with the resistor removed ~if the motor runs then the resistor is bridged

1 out of 1 people think this is helpful.

On my car the blower motor would not run without the resistor plugged in. I had all the same things happen with mine, don't know if it was a factor but at the time i changed my cabin filter also as it was pretty plugged.

1 out of 1 people think this is helpful.

Okay, now I can turn it off! BUT, it will only run on high when I need some air. Am getting really tired of this, so I'm gonna give it a rest for a while. When it irritates me enough again, I'll start pursuing.

I am also having the same problem. I have a 2000 grand marquis also i get a ticking noise wjen i lower the temperature it stops ticking when i put the temp. All the way.also cant turn tbe blower off so ive been just takn the fuse out when i dont use my heat or a/c. Bout time too fix any suggestion


I had the same high blower problem on my 2004 Grand Marquis LS with EATC. My diagnosis took a while but I finally fixed mine. All comments here are for an EATC system ONLY. The problem and solution are simple but hard to get to. What caused my high blower problem is that an important resistor in the blower resistor module under the hood loses connection with the EATC. This resistor sends back the blower voltage which tempers the EATC speed control. Without this signal, the EATC control range is offset too far to the high side to allow control. If you can take out the blower resistor module under the hood, the repair is easy. The actual failure is that the resistor module connector pins are soldered to the board with very little solder. Over time, stress and flexing crack the solder joints making an intermittent contact. The fix is to scrape off the yellow green coating to expose the entire bare copper pad around the connector pins then resolder with a lot more solder to give it strength. ALL the connector pins will fail in time so do all 5 pins while you have it out. Here's a picture with the two big ones done and the three small ones ready to resolder.

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