Fan control and blower resistor harness burnt

(recently bought a used 2008 base 4x4 dcb MT from stealership. For full story see my intro post)

I'm aware of the TSB for the blower resistor and plan to do that, however, it appears as if multiple wires and harnesses took a hit. Not only is the resistor pigtail burnt but my fan control as well.

Was removing the stock radio to transfer my Pioneer 4400 to the truck and had issues removing the connector to the fan speed control. When it came off one of the terminals was fried. The issue I was having was only high speed didn't work. I jiggled the harness to the resistor and now high is on low speed.

Has anyone else had or seen a post where the fan control fried as well? Or could I be looking at a stuck relay?

I'm curious as to what happened electrically because the cruise control and compass aren't working either. Compass has a burnt screen in the corner. But that's for a diff post.

 

I am currently working on the solution to this. I noticed this happened to mine as well, and sort of milked it along for another year or two, maybe three, IDK... it's been a long time getting around to taking care of it.

I can tell you this. There is a part number for the connector housing. I don't think it comes with any pins. Earlier this week I hunted down a replacement housing with pins. I also purchased a replacement control panel from eBay. The one I received is cherry. Once I confirm the connector housing I receive is for real the correct one and it has pins I'll do a write up.

This is the link to the Toyota part (I'm pretty sure, it came from another mega thread on this exact issue).

https://www.toyotapartsdeal.com/oem/toyota~housing~connector~f~90980-11615.html

 

I've only got a quick minute.

Fan control burnt. It happens. Not real often, but happens.
Cruise control. Possibly broken spiral cable(clock spring) Posibly covered under dealer recall.
Compass. 51 ohm resistor popped off the board. Burnt corner is part of the manufacturing process. Perfectly normal.

 

If the harness is still good and the pins clean up nice and ohm out okay then I'll just reuse it. It looks more like the current was too much.

I was going to bridge a 10 GAU wire from the blue/white to the resistor with solder and removable connectors so it could spread the current better until I saw the TSB with part numbers.

I'll hit the fan speed selector and harness with my Fluke and make sure nothing broke. Pray and reconnect. Probably did more damage removing it.

Oh, and I'll need to buy small files to clean up the contact points.

 

One and done. Bringing it into work tomorrow night to re-solder it into place.

 

Check out this nasty sumbitch. I took it apart and cleaned it all up a long time ago, then reconnected and forgot about it until I started having one of the backlights go out, (fixed via the Fonz method of popping it one).

I got curious last week and this is how it looks now. I need to revisit the blower resistor to see if that’s crispy again too.

 

Over heat from a bad/loose connection.

 

I'm sure the rresisto is good. The fingers/tabs(what ever the F they are called) are too small to handle the current so she hears up. Unless you did the TSB update, it probably got toasty again. This is where I was going to solder on a 10GAU jumper to help spread the current and not let it get hot but I'm too lazy and want to do it only once. So I'll order the parts from the TSB and get it over with

 

same thing happened to me...got a new resistor and wire harness connector. its updated and had thicker wires...splice the new one in as far away as possible to gain advantage of the thicker wires....

no problem since.

 

+1 for Fonz GIF

 

This has been going on in all makes of vehicles for decades. The friction fit of the connectors is marginal for the amount of current. In the past we just cut the wire both sides and used crimp connectors between them.

 

Spoiler: Before

Spoiler: After

I should have placed a bit more solder on the top one. Will see how long it lasts.

 

This SOB!!!!!
After bending the tab back on and putting the fan speed selector unit back in last night I tried the fan again......all speeds run smooth. I'll still have to replace the resistor and get the wire harness replacement. That was until I tried to check the resistor this morning to see how bad the connections looked...........

Spoiler

To my surprise the new resistor was in.

That means at some point someone replaced the resistor but didn't do the harness. When I looked into the updated version of the resistor I could see at all the contacts were burnt.

Spoiler

Now I have to figure out what caused all the contacts to burn on the new resistor and how so much current could have shot through the power supply wire, up to the fan speed selector, and melt the damn thing.

Oh, on top of that it appears as though the small resistor has seen some moisture cause the its corroding.......ugh

Spoiler

 

That corrosion most likely changed the value of the resistor which could explain the burnt connectors and wires.

 

The problem is how to clean that up. I do t have anything at home to clear corrosion from a circuit board. I could try to "knock" as much off as possible with alcohol and a q-tip but I'd still have to measure the resistance to ensure its good.

Since only the resistor was changed I might as well order a the entire resistor TSB and start from scratch. I think the total is under $30.........i think.

 

Try isopropyl alcohol and work the crud off with an acid shop brush. I normally cut the bristles down so they are about an eight of an inch long. If you’re lucky that crud is mostly solder flux coated with dirt.

 

This is the answer. The loose fitting terminals acts as a heater. That is why all the burning is localized at the connector and only a short piece of wire from the connector. If it was an over current condition the entire wire would be crispy.

 

So the fan speed switch melted because the contacts where loose either on the the switch themselves or the pigtail?

That's how I normally did it to work lose crud in hard to reach places. Or I'd use a gunners brush.

I'll look in the shed for an acid brush

 

Yes.

An electric heater element = A coiled wire with a resistance. The resistance reduces current by dispersing unused energy as heat.

When you have a loose terminal there is resistance. This resistance causes heat which burns (over time) the connector and wire locally at the source of heat. The heat also causes the connection to loosen more as time goes on which = more heat. Eventually the resistance is so great it no longer works at all.

They use the same principle to control the fan speed using the resistor pack. The heat is why it is installed into the air flow duct which keeps the resistor pack cooled down.