Heater Blower Fan Fix - Only High Speed
 

I did my search and found plenty of help.
I would like to thank everyone who contributes information. It sure helps.
I thought I'd contribute a couple pictures.

My truck ia a 1999 F150 with manual heat/ac (115,000? miles).
My fan was working on high only. With the clues from this forum, I went straight for the resistor. And look what I found...

Attachment 31484

Attachment 31485

From the amount of rust, I've apparently been missing a couple speeds for a long time. The melted plug could have been more recent and took out #3.

For a recap:
The resistor is located on the passenger side, under the dash, near the firewall. It's difficult to see.
If you look near the kick panel, you can see the wire harness and the plugs. Follow the wire to the resistor.
The two resistor screws are pointed straight up and mine took an 8mm socket. I removed mine by feel. (unplug it after you remove it, so you can see it better.)

Zeevert
http://i2.photobucket.com/albums/y48.../ZeeVert60.jpg

I picked up the new resistor today at the local Ford dealer.
p/n 4L3Z-19A706-AA
$28.14 plus tax
in stock

They didn't have the wire harness in stock, but it was going to cost over $38.

I "repaired" the old plug and put it back together. Fan works great.

Zeevert

One last picture under the Glove box...
Attachment 31486

Zeevert

Wow! I can't believe it rusted/melted like that. Nice article!

I just did this on my dads 01 f-250, it was slightly different, but the same concept. Good write up!

Just found this article was having the same issues. Mine also melted at the connector. I am logging this with NHTSA. This seems to be an obvious fire hazzard.

Jeremy

I just replaced the Resistor Pack (Board) on my 2002. Much the same scenario, but my connector was perfect. And an interesting thing was the amount of corrosion in comparison to the resistor packs on my 1986 and 1985 T-Birds (pulled near the same day). The T-Bird packs were corrosion free. Ths most likely has something to do with the Pack being on the bottom of the case in our trucks.

Cooter

I have the same problem with my 1997 F150. I didn't notice the harness trouble until after I had purchased the new resistor. I purchased the resistor based simply on the symptoms, before inspecting it. I would like more information on repairing the harness, which I would like to do without investing another $38. Are the plastic adapter ends pretty standard? If so, do I find them at an auto parts store or somewhere else? And are the wires soldered into it? Thanks.

Thanks it works!
 

My lower two blower speeds were not working and my AM radio was getting alot os static. Changing this resistor did the trick, now everthing works again. Thanks, Steve

Had the same resistor problem with my 95 Mustang. Looked the same, totally corroded. It went out around 70,000 miles. Good post.

was there a burning smell that came with this problem. cause in mine, a 92' flareside, i only have high blower speed, and a pretty bad burning plastic smell. where is it located, cause that would be very helpful

This thread was the reason I came to F150online! My fan switch only worked on possitions 3 and 4 (if they were numbered that's what they would be). I joined the site, did a search and in seconds I found exactly what I needed to fix my switch. I bought the part yesterday and did the swap in the parking lot of Ford (5 minutes tops) and just like that my heat works like new again. Thanks for the awesome write up and pictures!

Thanks! You made it too easy! Happy New Year!

I drive a '96 E150 with front and rear air. The other day the front blower suddenly quit, while the rear air (same control panel) blows cold.
Replaced the 60amp blower fuse under the hood, still nothing.
Slammed the door getting back in, and the fan came back on, but after shutting it off, no amount of door slamming helps.
Since the fan works on none of the speeds, should I first look at the switch on the dash, or the resistor?
Thanks in advance.

This happens because of oxidation of the connector causing high resistance, generating more heat, whhich creates more oxidation, etc. The trick is to exclude contact with air and moisture.

I had this same thing happen to me on my '99 F150. I found the burned/melted connector, and was able to find a good replacement in a local junk yard. When I put it in the truck, I made sure all the connectors on the resistor and on the plug were clean, and I coated the connections with a heavy coat of hi-temp silicone dilectric compound (regular "bulb socket grease" should work, too).

It's been like that for over a year now, and I checked it recently. No sign of any heating or burning - hopefully, it'll stay that way!

Where?
 

Look at the resistor first. That seems to be the most common place for this problem, mainly because of its location.

same issues here
 

I have the same issues with our 2002 F-150.It only works on high,and lately it is starting to smell like wires burning.

I'd also like to thank the OP. My fan speeds 1 and 2 stopped working about a month ago along with a burnt wire smell. Now today speed 3 also stopped, leaving me with only high speed. I came on here, did the search and came upon this awesome post along with pics and everything. This really is a great site! I'm going to take a look at it later today and see what I find.

Yup, sure enough the resistor was bad. Pulled it out in the parking lot of the auto parts store. Luckily the plug was ok. Chunks of rust were fell off when I set it on the counter. Pretty bad shape.

Blower Motor Resistor
 

My 1st time to this site and had to thank you for the great detailed photos and instructions......a $26.00 part at Napa and 20 minutes and I now have all 4 speeds back. Bluebobbybird, the photos were some of the best I have ever seen, the detail couldn't have been better. THANKS ('99 F150 XLT 5.4)

Just did this repair in about 10 minuets. What a great fix and write up. My blower would only work on High also in my 2001 F150 Supercrew. This will be great to now have 4 blower settings.
Great write up BlueBobby. A real life saver.
:beers:

heater blower fan fix
 

Thanks Bluebird, you saved me over $250. I also repaired my connector.
The clown at the Ford dealer wanted $300 to fix mine.
Great photos!!!

I had the same problem as BlueBobbyBird in my 1999 F150 last week; the harness melted at the connector and the resistor was rusted but not as bad. I replaced both and the fan worked on all four speeds...for one day. Now I have no speeds. I double checked the connections which are all good. It did not melt again. I also checked the mini fuses under the dash as well as the maxi fuse in the engine compartment; none of those are blown. It seems strange that I had high speed only before replacing everything, got all four back and now nothing???

Is it possible for the switch to go bad? Can someone walk me through testing the components? Or, is it time to throw my hands in the air and take it somewhere? Gotta have the defroster already here in Michigan at night!

Thanks in advance!

It sounds like the resistor element itself has blown. Take the plug off, remove the screws that hold the resistor in, and inspect it closely. If there is any break in the wires, that's your problem. They're cheap, and relatively easy to replace.

Great work, thanks
 

Thanks a lot for the great thread. I had purchased a resistor, turns out it was the wrong one anyway. When I removed the existing one to make sure they ordered the correct one I noticed the burning, (mine was much worse than the pictures). The resister was corroded but still worked so I just rebuilt the connector and it works like a charm. Thanks again I would not have known which wires to pull without the pics.:beers:

PS Should Ford not be worried about lawsuits when the vehicles catch fire because of this, mine must have been very close.:mad:

Quit. Removed, fiddled, reinstalled. Works!
 

Wonderful thread.

First, let me say that BlueBobbyBird's photos were some of the best I've seen for troubleshooting. Thanks a million.

My 1999 F150 lost all but the high speed of the blower about three weeks ago. I suppose it could have lost the lowest speed, but I can't hear that most of the time anyway, so I really can't say it was lost.

Following BlueBobbyBird's photos and my Chilton manual, I was able to find the wire harness with its three plugs, and the resistor block.

I disconnected the three plugs of the wire harness and saw that the white plug of the wire harness had its plastic scorched and melted-away around the usual receptacle.

Then I pulled the resistor block and saw its corresponding conductor blade showed signs of overheating--the black plastic of the connector was melted around the blade corresponding to the receptacle of the white plastic plug of the harness. The three resistance coils were in perfect shape, and I think the thermal limiter was OK, too. (I measured it with a volt-ohm meter and it read high resistance one way and low the other, and I hope that means it's OK.)

I fiddled around, scraping the metal of both blades and receptacles--of the block and of the white plug of the harness. After about a day of dithering, I put the block back in and then reconnected the harness. I turned on the heater blower switch, and it again works on all speeds.

I'm guessing a high resistance developed at the contact between that particular receptacle of the white plastic plug and its corresponding blade contact of the resistor block connector. The high resistance caused heat and caused the melting. Eventually the resistance (from corrosion, probably) interrupted the current for all but the high speed setting. When I disconnected the block from the white plastic plug, this might have rubbed-off some of the corrosion products and left good metal. The scraping I did while the components were out may have helped, too.

Before I found that the speed control was working again, I ordered a replacement "blower resistor kit", Dorman 973-414, from RockAuto, and it is in the mail as I type, and cost $33.80, shipping to North Dakota. The kit has the resistance block and the white plastic plug with pigtail wires, so I'll just cut the old connector off and splice the new one into place and should be "good to go." I intend to follow ExTex's good advice and smear some anticorrosion grease on the contacts between the new block and the new white plastic plug.

As for the $33.80, I suppose I should consider that money an insurance premium, because who knows how long the "fix" I did on the old connector and the block is going to last?

Blower fan and heat
 

I have the same problem with the fan only working on high and will be checking this resistor momentarily but I also have another symptom that occurred at the same time. The temperature does not seem to adjust at all. It does not get to cool or hot. This started at the same time as the problem with the fan speeds.

Has anyone else had this problem?

Fan Speeds
 

I had a similar problem. Glad I checked here. I didn't know about the resistor pack. Thought it might be the switch or the motor. I had speeds 3 and 4 working so I pulled the resistor pack. The connector was in good shape so I didn't have to deal with that. After inspecting the resistors I saw the problem; the second resistor was broken off the connection. Went to Napa Auto, $19.99 + tax and put it in pretty quick.

Overheating and corroding connections on the blower system is not just a problem on F150s, or even on Fords. I have had exactly the same problem on a Chevy van, a Dodge minivan, and I have even fixed the same basic problem on a Mercedes sedan! Apparently, running the blower on "high" for extended periods of time (maximum current draw) is what leads to the difficulty: if one contact somewhere is making slightly less than perfect contact, it generates heat, which accelerates oxidation (corrosion), which creates more resistance, which makes more heat, etc.
How do we avoid this issue? Well, I don't know about the rest of you, but I have gone through all the connectors on the blower circuit on all (3) of my cars, cleaned the blades and sockets, and coated them with DC-4 silicone grease. I also make it a practice to limit the amount of time I run the blower on high, and have instructed my wife to do so as well, under penalty of having to fix it herself if she burns up a connector! It's been working for over a year, and I have high hopes for the future.

What a great thread. Can't wait until tomorrow when I can look at my 1997 F150 which only has two speed on the fan left. In the spring I will check my 1999 Ford/Winnebago Motor home which only has the high speed left.

This seems so simple but when I had the motor home into Ford the Tech said it would be too costly to fix. Can't wait to see what the real problem is.

Blower works on high only
 

I have the same problem. Is the resistor in the same location on an 09?

I can't speak directly to an '09, but it's always been in the same place (in the fan plenum) on every thing I've ever seen from Ford.

Fire problem?
 

I've seen a fair number of these in the several months since I first came to this post, and I have seen a lot of melted plugs, corroded contacts, broken resistor wires, and etc. To date, I have not seen or heard of any fires cause by this proble. So, I decided to experiment.

I took one of the old, melted plugs that I had left over from a repair. I made a wire support in a vice, and applied a low flame from a propane torch to it. The plastic first melted, then charred, with minimal flame. As soon as I removed the torch flame, though, the plastic stopped burning (it smoked a bit, and stunk - a lot!) Apparently they selected a non-flammable plastic for this application - and wisely so, too!

So, I imagine the chance of a fire starting from a similar problem is remote. However, if you ever happen to smell a really nasty chemical burning odor while you're driving along, this is probably a really good place to look!

Not sure that the cause is the same in the trucks, however I had an early 90s Escort with the very same type of issue. Come to find out the cause is due to debris build up under the windshield wiper couling that cause water to backup and over top the heater system intake that is located under the coul. The only fix I ofund was to make sure and clean the debris out regularly (the maple seeds have a wonderful way of blocking up the coul area drainage).

heater blower blows high 2004 ford f150
 

So what part do you replace?

My blower only works on high, but i dont have heat at all. The resistor only causes the other 3 speeds not to work right? or does it make the heat not work either? and i took mine out, i dont have a melted plug, the resistor is corroded but no parts are melted or broken off.

The resistor only controls fan speeds, not the heat itself. If you're not getting heat at all, you might want to check the switch and/or control panel. It's probable that the vacuum operated doors aren't working probably. You should be able to hear them move when you operate the heat control from "OFF" to "FLOOR". If not, there's a problem with the vacuum system somewhere, and you'll have to trace it down.

As far as the blower only working on one speed, check the resistor carefully, and also check it with an ohmmeter to make sure the element doesn't have a break in the resistance wire somewhere. You should be able to read continuity between all of the blades, with the highest resistance coming when you read through the contacts on the ends of the elements, and the lowest when you read from the contact for the power lead through the largest resistance element.

If the resistor checks good, you're going to have to pull out the switch and check it out. It's possible for the switch itself to go bad: I've seen it a couple of times on other vehicles. Other than that, you'll have to do some basic wiring troubleshooting.

Good luck!

wire burned off
 

On mine the fan switch just stopped working. I found the wire harness and the black wire was out. The plug was melted where the black wire was connected. Anyway I can't remove the plug from the resisitor because of the melted plastic. Tried to pry it out but don't want to break it but maybe I should because I probably need to buy the wire harness too. Any Ideas?

Wow!
I hadn't checked my post in a loooong time. I'm very happy it helped so many people. It's crazy how a scary problem has such a simple, low-cost solution.

Just buy a new resistor, or maybe go to a junkyard and find a good resistor and harness, They're cheap, and once you follow the ideas given here, it won't be a problem any more.

By the way, since fixing the problem in my old '99 F150, I have sold it and got a '03 Heritage Edition. The blower was working fine, but on a hunch I took a look at the connector at the resistor. Sure enough, the plastic showed signs of high temperature! I did the whole bit: i.e., cleaning, silicone grease, and etc., and put it all back together. After over a year, it doesn't look any worse than it did when I got it, and I expect it to last for a long time.:p