Blower not running on '03 Grand Marquis

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  #1  
Old 08-14-07, 05:28 AM
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Blower not running on '03 Grand Marquis

OK, fst the basics:

2003 Mercury Grand Marquis. 4.6L 8, automatic transmission

Well maintained, all fluid changes on schedule.

The problem is that the blower does not come on. A/C compressor comes on and cool air is felt at the vents, though not blowing.

Have checked the fuses under the dash and the blower fuse ni the box under the hood. Cannot check the relay beacuse I am not sure how to remove it. There are 4 of them, and they all seem to be well seated. I am afraid to simply pull on them without some advise in that direction. I would not want to break something and be worse off.

Has anyone removed a breaker/relay? Any tips or suggestions would be appreciated.

If that does not turn out to be the problem, then I'll troubleshoot the motor.

Any suggestions on resistance readings from the motor that can give me a clue?

Thanks.
 
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  #2  
Old 08-14-07, 06:19 AM
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Quite a common thing with heater blower fans
Take the plastic part of a screwdriver and hit the fan. Do it a fair bit but dont smash it of course.
My fathers truck we just kick the air box area by the passenger area and that gets it going.
It might not be the fan but it is easy to check.
 
  #3  
Old 08-18-07, 03:00 PM
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Well, I have done some troubleshooting. The motor works when I use a different ground from the wiring harness "ground". In other words I get 12 volts to ground when I jump from the hot wire in the harness to the hot spade connector at the motor, and then run the other spade connector to ground. In doing this I am jumping around the other harness connector.

When the connector is installed properly or I jump from the harness connectors to the spade terminals on the motor, nothing.

Of course when I jump around the spade terminal at the motor as described above the climate controls have no affect, the motor just blows on the highest setting.

Any suggestions?

I know the relays and fuses are fine. I have checked all of those that are listed as related to blower, blower relay, and climate control. All pass continuity tests on the DVM.
 
  #4  
Old 08-18-07, 03:14 PM
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Can you get your hands on another control panel? Fan sounds like it's in working order since jumpered it.
 
  #5  
Old 08-19-07, 07:40 AM
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Not easily. Trying to follow the wiring harness at this point. Does anyone happen to know if there is a resistor system in the '03 like earlier models? Apparently they controlled the fan speed in those models.

Otherwise, I guess I have to start trying to figure out how to get the control module out of the dash.
 
  #6  
Old 08-19-07, 10:13 AM
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More troubleshooting info.

I have removed the control module from the dash. No evidence of any problems.

I also put my DVM on the voltage across the two connectors at the wiring harness and tried various controls. I am getting millivolts to about 0.4 volts registering when I change the fan speed wheel control. Except for the highest setting, there is a pulsing pattern from 0 to 60 to about 160 then back to zero.

The higher the I set the fan the faster the pulsing and the higher the high voltage, up to 200 MV.

At the highest setting it stays steady at about 0.4v.

So, something is varying with the setting on the wheel. In auto mode, I can get the same pattern by varying the desired temp from above outside temp to below outside temp. Faster pulsing occurs the lower I set the desired temp.

I know I am getting 12v at the hot wire to ground so the relays and fuses are fine. It appears to be something in the control circuit.

Anyone know anything about how these control circuits are set up and what to try next?

I also got this pulsing pattern at the relay box by removing the blower relay and testing across the two smaller wire sockets. There are 4 wires at the relay, two heavy guage, and two small guage. Across the heavy guage - 12V. Across the small guage, the pulsing pattern.

The two heavy guage wires go to (1) the heavy duty fuse in the relay box and then to the 12v at the positive battery terminal via the fuse bus, and (2) the positive terminal at the blower motor. So, current goes from the battery through the fuse to the relay and on to the blower. The other two wires at the relay, I guess control the speed of the motor? Maybe not. I am not sure whether this is simply an on-off relay or something variable. Also, I cannot trace the other connector at the blower. It disappears into the wiring harness and I do not see it emerge anywhere either at the relay box or at the control module. The control module has small guage wires connected at the back.

I see wires heading from the wiring harness that the blower wires disappear into to connectors at the firewall, but cannot determine whether they have anything to do with setting the blower speed.


Other than changing the control module, I am stumped. Someting tells me it is not the control module, though that is certainly not based on anything other than gut feel.
 
  #7  
Old 08-19-07, 12:35 PM
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You say battery to fuse to relay to blower. Are there only 2 wires on the relay? (you'd think there'd have to be more), and what gauge are they compared to other big and small gauge wires you have been looking at.
 
  #8  
Old 08-20-07, 11:50 AM
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Sorry, I was not clear. The relay has 4 wires to it as follows:

2 are heavy guage, same as the leads to the blower. One of those is the same wire as the hot lead on the blower. The other is a wire to the fuse in the relay box that is between the relay and the (+) terminal of the battery.

The other 2 are smaller guage. Those are the two I was referring to that I believe are control wires.
 
  #9  
Old 08-20-07, 05:08 PM
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No. I apologize. You WERE clear. Somehow I missed the paragraoph describing the 4 wires and your tests.

With relays like this that I am familiar with, where there are 2 small and 2 big wires, the one big wire is your incoming power, then power is sent to the switch (blower) then comes out of the blower switch as the 2nd small wire back to the relay, then the now energized small wire activates a contactor of sorts in the relay and bridges the two big wires to each other to allow bigger amps to continue to the blower.

I doubt this is your problem, as you say you have 12 volts going through the two big wires (but I am curious how you conducted all the tests with the 4 wires, and what you did with the switch positions while testing).

Have a feeling that already posted suggestion that trouble is in the board is most likely it. We know it's not the blower. And more than likely is not that relay also.

Not unless that relay is a resistor. You'd need someone to tell you that or look up wiring schematic on it, say in a Mitchell's wiring diagram, where they show the symbol for resistor as opposed to switching lines associated with a simple contactor. Then you'd know.
 
  #10  
Old 08-21-07, 06:39 AM
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After continuing to troubleshoot and research, I found a part that appears to be the newer version of the resistors that used be attached to the heater core cover in older models. It is a blower speed control and is attached on the right side of the heater core, in an almost inaccessible spot.

The dealer wants $46 for it. Based on some other boards' discussions and my tests, I am going to go ahead and replace this part. It is the most logical culprit at this point, though no guarantees of course.

Thanks for your suggestions.

As for my tests, I was simply reading voltages across the blower motor terminals while varying the motor speed at the console control.

Also, I did the same for the two small wires at the relay with the relay removed.

Both of these tests yielded the variable readings and pulsing from 0 to 200mv.

I also found a diagnostic test for the dash control module.

Press OFF and FLOOR simultaneously, followed imediately by AUTOMATIC.

This will cause a diagnostic sequence to run that will report any trouble codes. Takes 20 seconds or so to run.

I got a code 25 which indicaates a fault in the blend door actuator. I could find no such fault as the blend door seems to work fine. I can watch it work through the glove compartment opening. Also, the vacuum controls seem to work fine as well. I can watch them work through the dash after the control module is slid forward out of the dash.

Could be that the code was set in the past and then never cleared.

If this is a problem, the blower motor still needs to be fixed. One thing at a time.
 
  #11  
Old 08-21-07, 02:52 PM
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Just for your info

Just for your info I just went thru this on a 94 Caprice. If the blower moter is bad it can and will take out the speed resistor.(to much resistance).
 
  #12  
Old 08-22-07, 05:28 AM
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Any way to test the motor for this?

When I removed it I could see plenty of brush left, it turns as freely as the replacement, and it sounded perfectly normal when I jumped around it to the battery and it ran full throttle.

Thanks.
 
  #13  
Old 08-22-07, 05:28 PM
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No test

If your motor runs smooth and fast with straight battery voltage at all angles it is good. Mine on the caprice would only run if you held it upside down. Bearings going bad I assume.
 
  #14  
Old 08-23-07, 05:32 AM
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Thanks. I assumed I would remove the motor and find bad bearings. I have had experience with that on my heat exchanger blower in the house, so figured that would be it. When she ran solid and steady on 12v direct from the battery, I pretty much concluded the problem would be found elsewhere. Too bad, that was a 15 minute repair and $10 cheaper than the motor controller part, if that fixes it.

But it will be what it will be. I'll get back in there Friday night hopefully. Thankfully it has been cool this week in VA and we have enough cars to go around.
 
  #15  
Old 08-28-07, 07:39 AM
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Well, just to close this one out, I replaced the blower control module ($48 at dealer) on Saturday - the day it went to 104 degrees in this area. So, I cannot say it was "no sweat."

Anyway, I had to remove the heater hoses and a vacuum assembly/hoses to get to the part which is way back against the heater core enclosure, just left of center when facing the car from the front. It took me about 2 hours to do the entire job, and I tested the new part by hooking up the wiring harness to the module before installing it to make sure the blower came on. It did.

Other than the difficulties accessing the 2 screws, the module itself extends into the housing about 3-4 inches, so getting it in and out of its opening was tricky. Not a lot of clearance back there. I used a flexible drill attachment to get to the top one (I call these sorts of things "trick" tools), and a small open end wrench to get to the other one 1/8 turn at a time. Patience.

It has been working just fine now for three days with no problems.

I re-ran the diagnostics routine on the control module and get no errors, so the error 25 I was getting before must have been related to the malfunctioning control module.

Thanks for all the advice and help.
 
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