[amc49]

Maybe not the later stuff which is low volatility, the smell of vinegar is pretty much gone. Seem to have no trouble sealing up normal 12 volt stuff with it. Maybe sensitive low volt electronics yeah. Although I have 2-3 places now in sensor pigtails where I have patched in small crimp connectors at $.25 each to not buy a $20 pigtail. I drill out the pigtail outer plastic housing for room to install the crimp then flood the inside with silicone to waterproof it. No trouble yet and they have been on there a couple years. It'll be fun peeling that connector apart but who cares. I loathe $20 pigtails, they should be maybe $3-$4. Just like the $4 bulbs you get at parts store that only costs them forty cents a pack. Screw city there.

 

[FocusKnot]

You're right. I guess to clarify myself, I should say that there are RTV silicone formulations out there that are okay to use with electrical circuitry. The really bad ones have the strong vinegar smell. If that odor is missing or very light, it might be okay to use. I just prefer to stay away from RTV altogether rather than to try and figure out which ones will do harm and which ones will not.

 

[amc49]

The strong smell ones will waste O2 sensors pretty quick too. Why the stuff was reformulated.

 

[FocusKnot]

I believe the O2 sensor issue for sure!

I had a really bad experience with RTV and electronics many years ago. I have stayed away from it since that happened.

I have used some other silicone sealants that release methanol and ammonia during the cure process. So far I haven't noticed any problems with them.

 

[FocusKnot]

Since the discussion of what causes the connector to the Focus radiator fan resistor assembly to fail was brought up, I thought I would do an autopsy on my connector.

Photo 1 shows the wiring connector. Notice that the right-hand terminal has sustained more damage than the left. This is comparable with the majority of other photos I have located on the Internet. The resistor connects directly to the right-hand terminal and the thermal fuse connects to the left-hand terminal. That’s the first clue that resistor temperature is playing a role in the failure. More heat would reach the right-hand terminal than the left because the thermal fuse provides some heat buffering. (The item on the right in this photo is the part I cut off the resistor assembly.)

Photo 2 shows the connector cut open. There appears to be no signs of corrosion due to water entry either through the back (around the wires) or front of the connector. Oxidation is apparent on the part that contacts the male terminal. This is consistent with operation at high temperature.

Photo 3 shows the two female spade terminals. Notice that the terminal has four tangs to provide pressure to the part that mates with the male terminal. Also note that the connector is not closed as if the pressure tangs have lost their spring. This may be due to overheating or maybe it was made that way.

Photo 4 shows a washer of similar thickness to the male spade terminal inserted into the female terminal. Contact between the washer and the terminal is only made at the tips right where the pressure tangs are located…a very small area.

Photo 5 shows how I made a repair by drilling a hole in the male terminals and attaching ring terminal connectors as I described in my earlier posting.

I measured 4.55 volts across the resistor with the fans running. The resistor measured about 1 ohm. That means about 21 watts of heat is being generated. Most of that heat dissipates into the air, but apparently a lot must be traveling down through the resistor assembly terminals to the wiring harness connector.

The challenge for any electrical connector under the hood is making and maintaining the required mechanical and electrical connection over a wide temperature and humidity range. A good low resistance connection is mainly dependent on the (1) surface contact area between the mating parts combined with (2) sufficient pressure. This connector appears to be lacking those two key ingredients. In my opinion, this connector is not well suited for this job and is failing due to heat from the resistor. Perhaps in newer models Ford has changed the connector type. Let’s hope!

 

[burnie]

Good write up and explanation!!! Can`t wait now till one of the newer units go bad....the ones with no male/female connections showing , just a pigtail only .
I wanna` see what Ford has done on them to try to solve the problem .

 

[amc49]

That #5 pic should work well like that, mine implemented a bit messier since it melted more but same thing done there. I bypassed and removed the thermal since it doesn't appear to work anyway. Just keep an eye on it, but should be bulletproof. And much cheaper than new part which will melt again.

Excellent, I'm sure others will appreciate the #5 pic to easily illustrate the idea.

They are getting to where they don't care so much about the reliability of the parts, more is being put into allowing parts to go together by hand with no tools used at all and quick. Lots of electrical troubles beginning to show in ALL cars now because of that mindset. Many more fires in cars now than used to be..........

 

[FocusKnot]

I agree that reliability seems to be taking a backseat nowadays. This problem started on my car when I had only about 70,000 miles on it. If I had 170,000 then I would expect things like this to be going on.

I'd like to see one of those new "pigtail only" units. Ford must have realized that they had a design flaw and totally took the connector out of the equation.

 

[burnie]

FocusKnot...that or they decided they could make a few extra $$ by selling the whole unit rather than just the connector . And the new pigtail only units..where the male lugs come out , there`s just the 2 wires poking out . Seems to be sealed with some kinda` hard setting glue/gel . Not fancy at all .

 

[FocusKnot]

Ah...I can picture that. Thanks Burnie.

 

[Blue5ive]

Good thread as I believe I need to change mine as well. Thanks for the photos FocusKnot.

 

[FocusKnot]

Go for it Blue5ive!

I used the following stainless steel (no rust wanted!) hardware (2 each):
#6-32 X 3/8” screw
#6 lock washer
#6-32 nut (1/4” width)
1/4” ring terminal (crimped and soldered…overkill, but that’s the way I am!)

I used a 1/8” (.125) drill bit and reamed the hole a little by tilting the bit. A 9/64” (.140) would be the normal bit to use for a #6 screw, but I broke mine and haven’t replaced it yet.

I am going to seal with JB Weld later. I have some of the 4-minute KwikWeld on hand. Sealing with JB Weld will (1) protect the repair from moisture to prevent oxidation, (2) prevent movement of the hardware, (3) allow for heat to escape freely (JB Weld conducts heat fairly well), and (4) electrically insulate it. Note: This repair might survive just fine without any coating whatsoever.

There was a concern about JB Weld being an electrical conductor, but I went to the JB Weld website (jbweld.com/faqs) and found this:
Q: Will J-B Weld conduct electricity?
A: No. J-B Weld is not considered to be a conductor. It is an insulator.

Given the problems this radiator fan resistor connector is causing, maybe it should be on everyone’s schedule for regular inspection. It would be easy to unplug the connector and check it every 10K miles, every oil change, or whatever. Oh, I saw on another website that a guy said to pry the metal clip off at the side to get the plug loose. No! Just push the clip in towards the connector to unlock it.

I hope it works out for you.

 

[amc49]

Wonder what they changed in the JB, they themselves used to say the dark grey was from ground up aluminum in the mix to make it stronger holding to itself..............maybe stopped and now dye only? Maybe to increase possible use of product as electrical potting compound. One never knows.

 

[FocusKnot]

Yeah, who knows?

Yesterday I checked the resistance of some JB Weld (regular, not KwikWeld) that I had used on my mailbox. It measured infinite resistance on my meter. And, my mailbox was over 100 degrees too! So I feel comfortable using it.

Even if it did have SOME conductivity, it would probably still work fine. A few Kohms in parallel with 1ohm is still 1ohm. If this was a sensor such as the MAF, we would definitely have to consider ANY conductivity.

 

[my_beautious_ZX3]

JB Weld?
On a mailbox??
In Texas???

There's alot of jokes in there, fellas. But, I'm not sayin a word. Your secret is safe with me.

 

[FocusKnot]

Ha-ha, very funny! I was adding a feature to my mailbox. You would have to see my YouTube video about it to understand.

………..and no, I’m not giving you the link to it…this is an automotive forum.

Now let’s turn our attention to a more serious matter:

The purpose of the thermal fuse​

The thermal fuse is incorporated in the fan circuit as a protection for a short circuit downstream from the cooling fan resistor assembly. Let’s do a little math to prove that.

The low speed fan circuit is protected by a 30A fuse. The resistance of the radiator fan resistor is about 1ohm. So, if a short circuit occurs AHEAD of the resistor, pop goes the fuse. But if a short circuit occurs AFTER the resistor, the maximum current is limited by the resistor. Now the math…

Ohms Law says I=E/R. So, a short circuit AFTER the resistor in the wiring harness or internally in either of the two fans would yield about 14 amperes (I=14/1, assuming 14V running voltage). This would not blow the 30A fuse. However, here is what would happen…

Again Ohm’s Law says W=I squared X R. So, W=14 X 14 X 1 or 196 watts! Yes, that’s 196 watts as opposed to the normal 21 watts in the resistor assembly.

Theoretical news headlines:

Car bursts into flames during rush hour on I-30 and snarls traffic for hours.​

Moral of the story here…don’t run without a thermal fuse if you value your car.

 

[amc49]

You are correct of course. Got me questioning the worth of the 30 amp fuse though. If only protecting the wire run to resistor then why does the high fan one have to be 50? Seems to me the 30 was picked with a view of total circuit current flow there, not just as a supply wire to the resistor protector. And, what stops high fan from burning car to the ground if it doesn't pop the 50? One ohm resistor gonna change things that much?, the wire itself has that kind of resistance in a long piece..........can't help but think the thermal's location says much to do with temperature RIGHT THERE not current at fans later. As in stopping meltdown in a plastic fan shroud. Or stopping a short right at resistor across the coil.

Any meltdown otherwise would have to pretty much be a fan, and fans are one of the more reliable parts on these cars. I've never changed one ever on the last five I've owned. Of course that can always change.

 

[FocusKnot]

I looked over the wiring diagrams for my car. In low speed operation, the current for both fans is fed through the 30A fuse and the resistor. In high speed, the current for both fans comes from the 50A circuit and is fed directly to the fans bypassing the resistor entirely. Four relays control all the switching.

The thermal fuse “looks” at the temperature right at the resistor. The resistor’s temperature would be a function of the current flowing through it…either to the fans or to a fault in the wiring downstream. If one of the fans shorted out then that would essentially be the same as a short in the wiring to the fans.

The 50A fuse should blow on any short in the high speed circuit or the fans. The 30A fuse would not blow on any fault downstream of the resistor. A fire would most likely be started by the resistor in the fan shroud if the thermal fuse was not there to prevent it. If the entire resistor assembly was shorted out, the fans would run on high speed. However, the 30A circuit may not be able to handle that!

I searched many forums to see if the purpose of the thermal fuse was being considered. I found discussions where people were replacing them or bypassing them, but I couldn’t find anyone explaining exactly why they existed other than to say they are to prevent fires. No one was explaining the scenario that could lead to a fire. (Maybe it’s out there, but I didn’t run across it.) If people don’t understand the big picture, they may be tempted to bypass the fuse. I believe this forum has a unique opportunity to educate people and avoid the possible ugly consequences of bypassing the fuse. They are literally playing with fire! We are on this forum to learn and to pass along what we ourselves have learned to others. I know I have learned much from the posts to FF for sure!

The thermal fuse on this assembly is welded in place and would be very difficult to correctly repair. Also, its physical placement in relation to the resistor is crucial for proper function. If a person had a blown thermal fuse, a new radiator fan resistor assembly would probably be the best way to go rather than attempt a repair.

Thermal fuses can be found installed in several locations on today’s vehicles. Sometimes these fuses are soldered in place and repair can be fairly easy. When soldering a thermal fuse, be sure to keep the fuse cool with a wet rag to avoid destroying it.

 

[FoMoCus]

This thread was very useful. I've been tracking down a nasty idle drop and stutter when the fans kick on for a while now. First I though it was the alternator, then I replaced the alt pigtail, and thought about even replacing the fans. But when I saw this I checked my resistor and the plug started to fall apart in my hand. I did a similar fix to what was mentioned here, cutting the shroud from the resistor contact points, and cutting off the original plug from the wiring, but instead of ring terminals I used female spade connectors. I cut a piece of vacuum line and sliced it open and stuck that in between the prongs before wrapping everything in electrical tape, so that the terminals wouldnt touch. My problem seems to be resolved, we'll see if it holds up.

 

[amc49]

You do what you gotta do.

Agreed Focusknot, just that I've bypassed those thermals on other things and no troubles at all. Not that I go looking to do so however. Sometimes they are not apparently chosen with correct values, like here. To me it should be popping instead of melting the resistor plastic into carbon chunks. So, having the thermal there is useless at least in that application. I found one bad resistor by opening hood at the opportune time to find a wisp of smoke coming from it, how far behind was the fire? One reason I use silicone to seal the repair instead of epoxy there, the silicone will take much more temperature from the wire embedded inside it. So far mine appears to be and work fine, but I don't trust it, just like other electrical trouble spots on these cars, and look at it every time hood is opened.

And yes, you are correct, inspection of that connector as well as positive battery cable condition for the first 4 inches if using the stock cable should be part of an inspection every time one opens a hood on these.

Where's the thermal fuses on the dang brakelight sockets??? On my wagon I have to take a dremel and cutting disc and CUT the socket loose from the brakelight lens plastic to change a bad bulb, socket gets hot enough to weld the two pieces of plastic together. Abysmal, the science of fixing that has been known for 75 years yet they cannot get it right.