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Replacing blower fan resistors

professor229

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Need some brainstorming here.... I posted above about the resistor I pulled out.... and bought a new unit that looks exactly like the resistor I pulled out... but... with four black wires... I then laid the old plug and oriented it the same way as the new plug.... and wired in the four wires.... On the shake down cruise yesterday, I tried the fan... at least ALL FOUR settings worked instead of "off" and "high".... in other words, the two middle speeds did not work.. Now, with the new resistor all four speeds work except all four seem to be the same speed... "high".... So I thought I wired it wrong... and this morning I pulled it all apart again... air box, reservoirs and got to the resistor.... pulled the plug out, took off the protective loom and black tape, and then laid the old resistor (never throw anything away!!!) and followed the wiring..... all four wires were wired correctly... and I was hoping I screwed it up the first time.... bottom line is that I did NOT screw it up and the wires are correct... so... why are all settings on the switch making the fan speed on high???? ideas? and hope it is something simple... I can live with it this way... but would like to have it right..... all help/ideas are appreciated!!!
 


James Morse

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Hm, sounds to me like perhaps the unit is faulty? Too bad they didn't color the wires, but if you laid them out equally then it should work properly. I think all my speeds are different, but truck is waiting to get its new starter in right now so bad time to test.

With mine I didn't have to do all that dis-assembly, I just removed the air tube/box/whatever I didn't have to remove the reservoirs but had to get small socket wrench that I showed in the pics.

The other guys will know more. Just seems to me if it's wired correctly, and the unit has different resistors, it should work. Perhaps check that part is correct? I think I got mine at Advance. Good luck chasing it.
 

professor229

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Hey ... thanks.... and yes, I chased it some more.... I watched two guys on You Tube and the first one sounded like he knew what he was doing until he got to talking about the two possible other problems.... the fan being defective and a bearing going out making it harder to turn so it needed more juice... and the air flow being restricted by a dirty cabin filter.... So I investigated.... .a Ranger doesn't have a cabin filter.... so then back to the videos and the second guy probably told me the answer....... When I checked for the fan speed, I had the main switch "off" and then turned to "defroster" and ran the numbered dial that indicates speed... THAT was probably my mistake as this video guy dropped a little fact about these resistors as he went through his lecture on them... He talked about the lowering of the electricity as you go through the switch numbers BUT when you have the knob on "defroster" it bypasses the resistor... and is ALWAYS ON HIGH SPEED..... So tomorrow or whenever, I will go out and instead of putting the knob on DEFROSTER I will put it on one of the other choices and I am willing to bet that the speeds work fine.... Live and Learn??? I hope it is this simple!!!!
 

James Morse

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Wow that is some useful information, I didn't realize that. I guess it kind of makes sense because when your windshield fogs up that's totally dangerous so you want it cleared ASAP. Really interesting.
There's also some info about, on which settings it does/doesn't run thru the a/c for pre-drying. I think it's in previous posts in this thread, or, somewhere.
Yeah try it not on defrost and see what you get. Doesn't sound like you have these other possible defectives, so far.
I had not only the resistor problem, but also I was getting barely lukewarm heat, and (different thread) these guys here told me exactly how to flush things out and man, was I glad to have that heat working this winter!! Warms the cabin right up in no time. Of course today it's 85F here. The a/c is ice cold on mine, knock on wood, didn't have to mess with it.
Let us know how it turns out.
 

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As far as I can remember, every vehicle I've owned still allowed the fan speed to be adjusted when the defroster mode was selected.
 

James Morse

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There are two trucks. Both are sorted. Probably selling the '99.
yeah that's right mine uses all diff speeds on defrost, I just tried it
 

professor229

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I got to thinking about it and I guess I never realized it, but the same thing happens on my Chevy truck... whenever I switch it to defrost it seems to kick in to a higher speed.... like maximum and I know on the AC end of it there was almost two settings.... AC and MAX AC... and when you turned to MAX AC I am sure it bypassed the speed resistor and kind of roared a bit and made a different sound as the air flew out of the vents.... I was annoyed first, that I had perhaps wired the resistor on the Ranger wrong..... but spent so much time looking at it to determine if it could possibly be wired any other way..... there was/is no alternative... only one way to do it and I practiced the definition of insanity and traced the wires more than once expecting a different result..... and came to the conclusion that I did wire it correctly..... and there was nothing else to try.... That is when I checked on the videos and read the comment sections below the videos that I find invaluable or laughable some times..... and one guy mentioned the defrost bypasses the resistor... He also documented which color wire controlled what speed.... he was very thorough... but in passing he dropped a statement when he said the resistor was by passed when the know was turned to defrost.... This all bothered me but I had ten minutes and some ambition left and was annoyed at the results earlier in the day again, so I wandered out to the garage, and actually started the Ranger this time, and then moved the selector to "defrost" with he same results... high speed fan.. So moved the selector to the icon of floor heat and then tried the different speeds and there IS a noticeable difference.... in other words, it works right but in my opinion the fan still turns too fast.... but there are distinctive speeds and I can live with that.... I still do not know if the A/C works.... and honestly, don't care because I just don't use A/C that much and this Ranger will pull a boat trailer five miles to the lake launch and back home the same five miles....

I also found out that this same aftermarket resistor is used on MANY Ford models.... and that is why the wires were all generic black and not color specific for the Ranger... but the wires all went to corresponding pins and the plug could go only one way into the socket on the firewall.... I also thought that maybe there was a ground wire on one of the two bolts that hold the assembly on that I forgot to install but looked and nope.... and I don't remember any other ground wire.....

So this morning I am supposed to go after the alignment... anybody got any extra ambition they care to send? I still have some questions and need to watch a couple DIY you tube videos on this again.... A1 Auto does the best... and so does UHAUL in producing these videos.... they try to be professional for the most part succeed.. but the A1 video on DIY alignment skips a couple areas where information is needed ..... and maybe I missed it?? So I will go back and review....

and a ps... After getting two newer headlight assemblies from U PULL IT PARTS.... I cleaned them up... and had no idea if the bulbs worked in them but, they were the last thing installed. The reason I bought them is that the original adjusters on the Ranger were beyond rusted... no hope... so how could I adjust them.... Yesterday, when I got back from the shake down cruise, I got to the garage door and turned on the low beam and high beam lights.... If anything, they are too low..... but not by much and again... I will probably never use this truck after dark..... although I may leave to go fishing early in the morning so might need them then or in a fog..... but all the lights except one back up light works.... my goal was to make sure the headlights on low beam would not be pointed at oncoming traffic..... dangerous....

An a PS..... I suspect this Ranger, like most???? , has a factory installed four flat wiring harness... and it doesn't work.... my test device would not light up.... signals, brakes, nothing.... so there is no power to the four flat.... First thing I will do is see if there is a fuse for this.... is there? Anybody know? and then start tracing with a test light for a break.....

Enough... take care... and again... thanks for the ideas/suggestions.....
 

professor229

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No idea why..... but took the Ranger on its first "mission" yesterday... a trip to Menards... got about a half mile from home and needed some heat to take the chill out.... turned it to floor heat and turned the fan switch to high at first.... then down to the 2 setting with major drop in fan speed... seemed like it was still on high... and then, doing nothing.... it dropped down to a lower speed so I turned the switch to setting 1 and it was at a very low speed... 2.... faster.... three... quite a bit fast and then high... all the speeds were now working correctly..... hmmmmm what did I do to accomplish this???? nothing...... weird? Time to go see if the fuse is blown (hopefully) in the trailer light four flat plug wiring.... hope that is it.... save a lot of time trying to find the problem
 

James Morse

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There are two trucks. Both are sorted. Probably selling the '99.
As to fan speeds 'fixing themself' (which rarely happens), I'd suspect that the switch contacts were dirty and moving it around made them work. Only other thing I would think of is if the resistors in the unit were touching, or wiring somehow shorting across leads. Good luck with trailer wiring.
 

professor229

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Hey..... I think you hit the nail on the head with the switch perhaps being a little corroded from sitting... I bought this Ranger from my neighbor so I would have a project so it has been sitting for half a year.... and they never used the switch much because the resistor was so corroded/rusted that it only worked on "off" and "high" which they lived with.... I replaced the resistor and it was so corroded I could not remove the plug ..... even when I removed the whole unit, I put it in a vise and could not even use a chisel to get the male/female apart.... I still have it... a reminder... and when the new unit came in it had no color coding on the wiring but the four wires were pretty intuitive and they could honestly only be soldered in one way... but I even second guessed that I had somehow managed to screw that up so I dug in one more time removing the air box, combined reservoirs etc. to get to the new unit... removed it and double/triple checked to see if the wiring could go any other way... simply it could not .... I think your idea about the contacts in the knob is probably right... the bottom line is it started working after I started using the Ranger the other day... first time since the work on it began...

As for the trailer light four flat plug, I checked the fuse first..... and it was good.... so I checked the contacts where the fuse touched... and they also were good with a test light lighting up on one side.... So I knew the fuse and "juice" were good.... Next stop... back to the plug... and I had used a test plug in this twice before and it did not function at all.... but this time I tool a test light probe back and checked each with nothing lighting up just like the plug... and muttered a word or two that I am not proud of when I got a "flicker" on one of the contacts inside the plug... so I pushed the probe in a lot harder and got ALL of them to light... in other words.... the plug itself was corroded or whatever and I have several new plugs in the tool box.... dug one out, cut off the old one and installed the new plug.... and then tried the test plug... perfect... So at least I did not have to trace a wire from the back to the front.... That made my day.... PS... the plug wiring was so old/bad at the plug that there were four colors to the wiring, but the yellow was so faded it looked white....

Thanks again for your ideas/suggestions... it is very much appreciated....
 

professor229

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PS.... I have a FLICKR account for some of the work done on this project and one of the pictures included is the old resistor I pulled out and replaced... you can see how corroded it was... and it only worked on "off" and "high" which I think is 4 on the knob

 

James Morse

1997 XLT 4.0L 4x4 1999 Mazda B3000 2wd
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4WD
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235/75R15 but changing to oem 265/75R15 or more likely 31x10.5
My credo
There are two trucks. Both are sorted. Probably selling the '99.
That sounds like good news all around! Yeah good thing you didn't have to replace all the trailer lights wiring.
Might be good to get a can of CRC electronics cleaner, although, not sure you'd be able to get to the contacts in the fan switch. Probably just in normal use it will stay good, at least, if it's that - sounds like it was.
Great to get a few things knocked out isn't it.
 

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