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#2446153 - 01/27/12 05:00 PM Blower Motor Resistor Replacement
lmrogp Offline
Member

Registered: 01/02/09
Posts: 100
Loc: NV
I'm replacing my blower motor resistor, as there is not much difference between blower speeds 1,2 and 3 on my manual heater. Pulled the resistor, expecting the connector to show signs of heat damage, but to my surprise it looks OK. Despite this, does it make sense to always splice in a new connector when replacing the resistor?





I compared resistance between the old and new resistor. The old one reads the same value across all of the connectors...0.9ohm. While the new one reads three distinct values: 1ohm, 0.8ohm, and 1.3ohm. So I think it will make a difference. Is there anything visible to indicate the resistor is shot? What is it that fails...the coiled wire? Here's my old resistor...




Thanks...
_________________________
2002 Mercury Grand Marquis GS, Spruce Green, 153k
2001 Ford Crown Victoria P74, Blue, 150k+ (Stripped, RIP)
2007 Ford Crown Victoria P71, Dark Blue, 80k (Sold)
1997 Ford Crown Victoria P71, White, 200k+ (Sold)
1988 Ford Crown Victoria P71, Dark Blue (Donated)
1980 Mercury Grand Marquis, Silver (RIP)


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#2446159 - 01/27/12 05:04 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
P71Ham Offline
Climber

Registered: 11/18/08
Posts: 650
Loc: Parkersburg, WV
High bypasses the resistor, the rest of the settings go through it. The different resistances basicaly "chokes" the power to the fan. I've seen the coils melted together, and they'll do all kinds of stuff when they fail. The one in my prizm looks more like the style for the EATC, and the whole thing was black when I replaced it. Since theres no obvious signs of true failure in the old harness, or resistor, personally I'd leave the current harness in, but thats just me.
_________________________
'01 Crown Vic. P73. 145k. Ex college president's car.
Mods so far:Bumper tuck, Sony Xplod head unit, sidemarker blink mod, New OEM headlight housings from ADTR, BH1976 Headlight Relay Harness, $40 junkyard 70mm TB (More to come as $$$ permits)

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#2446308 - 01/27/12 08:08 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
LTDteether Offline
Over the Hill

Registered: 07/19/02
Posts: 4450
Loc: Democratic Rep. of Southpaw
The switch does not select a different resistor for each speed, but a different combination of resistors for each speed. As pointed out, full speed is no resistor. The lowest speed puts all three in series with the blower motor. That is why you always lose the lowest speed when any one resistor burns up although you might lose other speeds at the same time. The only setting that has only one resistor in series is the second to the highest speed.

Resistor failure is burning up of that nichrome wire resulting in an open circuit. You should be able to see the damage. Look closely and measure the resistance near the end of the coiled wire. Yours looks fine so I am wondering how it could be damaged elsewhere to have the symptoms that you do.

Take a look here: http://www.idmsvcs.com/2vmod/eatcswap/manualresistor.html
_________________________
'99 GM GS HPP.
I may not be a rocket scientist, but I *am* a scientist.

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#2446315 - 01/27/12 08:28 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
LTDteether Offline
Over the Hill

Registered: 07/19/02
Posts: 4450
Loc: Democratic Rep. of Southpaw
In a '99 the values of the individual resistors are rated at 0.5, 0.5 and 1.3 ohms. That means that the resistance (ohms) across that assembly should be from highest to lowest:

2.3
1
0.5

My diagram shows the circuit on that assembly is three resistors in series with taps between them. -1.3-tap-0.5-tap-fuse-0.5-ground.

That means that if you put one lead on the ground connector, you should get the 0.5, 1.0 and 2.3 at the others.

Note that the whole thing is on the ground side of the motor circuit while the on/off switch is on the battery side of the motor.
_________________________
'99 GM GS HPP.
I may not be a rocket scientist, but I *am* a scientist.

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#2446364 - 01/27/12 09:31 PM Re: Blower Motor Resistor Replacement [Re: LTDteether]
lmrogp Offline
Member

Registered: 01/02/09
Posts: 100
Loc: NV
I just re-measured with a better multi-meter. I connected the leads at the ends of each individual coil...the fatter coil is 0.5, and the two skinnier ones are each 1.3. The old bmr measures exactly the same, so the new one will probably not fix my issue.
_________________________
2002 Mercury Grand Marquis GS, Spruce Green, 153k
2001 Ford Crown Victoria P74, Blue, 150k+ (Stripped, RIP)
2007 Ford Crown Victoria P71, Dark Blue, 80k (Sold)
1997 Ford Crown Victoria P71, White, 200k+ (Sold)
1988 Ford Crown Victoria P71, Dark Blue (Donated)
1980 Mercury Grand Marquis, Silver (RIP)


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#2448084 - 01/30/12 03:33 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
LTDteether Offline
Over the Hill

Registered: 07/19/02
Posts: 4450
Loc: Democratic Rep. of Southpaw
Does your "single speed" blower seem to be locked in high or low speed? If high, it indicates that you have a short in the switch or in the wiring that couples all three wires together.
_________________________
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I may not be a rocket scientist, but I *am* a scientist.

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#2448103 - 01/30/12 03:57 PM Re: Blower Motor Resistor Replacement [Re: LTDteether]
lmrogp Offline
Member

Registered: 01/02/09
Posts: 100
Loc: NV
After further investigation, I think the blower is working ok. Its just that the difference between speeds is not that great. low is very low, too low to be useful...the two middle speeds are slightly faster but they are almost identical to each other...and then high blasts. Seems like a better choice of resistor values in the bmr would make for a more even distribution of speeds from low to high.

Thanks,
_________________________
2002 Mercury Grand Marquis GS, Spruce Green, 153k
2001 Ford Crown Victoria P74, Blue, 150k+ (Stripped, RIP)
2007 Ford Crown Victoria P71, Dark Blue, 80k (Sold)
1997 Ford Crown Victoria P71, White, 200k+ (Sold)
1988 Ford Crown Victoria P71, Dark Blue (Donated)
1980 Mercury Grand Marquis, Silver (RIP)


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#2448307 - 01/30/12 07:57 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
LTDteether Offline
Over the Hill

Registered: 07/19/02
Posts: 4450
Loc: Democratic Rep. of Southpaw
The most likely problem with the blower motor is that the bearings wear out and cause a lot of drag. That will cause over-current melting connectors, resistors,....

At one time, I knew how much current a normally-operating motor drew, but Katrina washed away those notes. You could check it. If it is drawing anywhere near the fuse rating for that circuit after the initial surge, it is probably bad.

I'd pull the control switch and resistor connector and then check for continuity between wires where there is not supposed to be a connection.

You have a spare resistor. You could get some nichrome wire and wind your own resistors.
_________________________
'99 GM GS HPP.
I may not be a rocket scientist, but I *am* a scientist.

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#2845031 - 06/26/14 12:51 AM Re: Blower Motor Resistor Replacement [Re: lmrogp]
lmrogp Offline
Member

Registered: 01/02/09
Posts: 100
Loc: NV
Update...regarding my blower speed issue.

The problem is that speed MED-HI is no different than speed MED-LO. So the other day I was messing with the switch, and found that if I set at a sweet spot between MED-HI and HI, I would get a fan speed that was an actual MED-HI (faster than MED-LO and slower than HI). Got me to thinking that the switch could be the problem. So I ordered a new one, and after installation all four of the fan speeds (LO, MED-LO, MED-HI, HI) are working perfectly.

I was curious to do a comparison of the original switch and the new one, so here's a few pictures.

Not much of a difference on the black plastic.




On the plug side you can see the age difference.




I popped open the old switch and here's the root of the problem. A ridiculous amount of corrosion, I assume age related, on the contacts.




So in my case, the blower motor resistor and its plug looked good, and my fan speed problems were strictly switch related. It's something to look at if you ever have a similar blower speed problem.

For my 02 MGM, the switch is YH-588, also known as F4DZ-19986-A.
_________________________
2002 Mercury Grand Marquis GS, Spruce Green, 153k
2001 Ford Crown Victoria P74, Blue, 150k+ (Stripped, RIP)
2007 Ford Crown Victoria P71, Dark Blue, 80k (Sold)
1997 Ford Crown Victoria P71, White, 200k+ (Sold)
1988 Ford Crown Victoria P71, Dark Blue (Donated)
1980 Mercury Grand Marquis, Silver (RIP)


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#2845864 - 06/30/14 05:27 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
PHoganDive Offline
Over the Hill

Registered: 06/11/11
Posts: 1465
Loc: Mass, USA
Originally Posted By: lmrogp
I popped open the old switch and here's the root of the problem. A ridiculous amount of corrosion, I assume age related, on the contacts.




So in my case, the blower motor resistor and its plug looked good, and my fan speed problems were strictly switch related. It's something to look at if you ever have a similar blower speed problem.

For my 02 MGM, the switch is YH-588, also known as F4DZ-19986-A.



That's not 'corrosion' damage, its from arcing. The blower motor takes a lot of power to run, and if the switch contacts don't make excellent contact, they can arc, and melt the metal of the switch contact.
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#2845956 - 07/01/14 04:03 AM Re: Blower Motor Resistor Replacement [Re: lmrogp]
95CrownVictoriaP74 Offline

Posting Addict

Registered: 11/28/00
Posts: 16485
Loc: Volusia County, Florida
Interesting. Thank you for the photos.
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#2846035 - 07/01/14 02:29 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
1 Adam 12 Offline

Over the Hill

Registered: 07/04/01
Posts: 1488
Loc: Glendale, AZ
Actually its interesting you found that. EricTheCarGuy (famous YouTube mechanic) found the same exact thing on a 03 GMQ. Search for crown vic blower speed or something like that...
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#2846622 - 07/04/14 06:03 PM Re: Blower Motor Resistor Replacement [Re: lmrogp]
Vicinator Offline
Rookie

Registered: 04/18/04
Posts: 60
Loc: Ohio
I think someone noted to replace the blower, I second that and make sure the connections, including ground, are good.

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#2847063 - 07/07/14 05:56 PM Re: Blower Motor Resistor Replacement [Re: PHoganDive]
lmrogp Offline
Member

Registered: 01/02/09
Posts: 100
Loc: NV
Thanks for the clarification re: arcing. So was that bad switch a fire hazard? I'm pretty sure it was original, which makes it approx. 13 years old.

Thanks,
_________________________
2002 Mercury Grand Marquis GS, Spruce Green, 153k
2001 Ford Crown Victoria P74, Blue, 150k+ (Stripped, RIP)
2007 Ford Crown Victoria P71, Dark Blue, 80k (Sold)
1997 Ford Crown Victoria P71, White, 200k+ (Sold)
1988 Ford Crown Victoria P71, Dark Blue (Donated)
1980 Mercury Grand Marquis, Silver (RIP)


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