30A fuse for fans blowing after replacing fuse box and alternator cable

[OlyTDI]

Gotcha. I think given that it isn't a sure thing that a replacement is going to address the fuse blowing issue, I probably ought to go with the lower end. I also like the idea of being able to return it.

I'll also call IDParts tomorrow and get their opinion on durability/returns for the different brands.

 

[Genesis]

Advance has it if you want it "now" and if it pukes its lifetime replacement so they'll give you another one; $150. https://shop.advanceautoparts.com/p...-799/19010457-P?searchTerm=Engine+Cooling+Fan

Chineesium it is. I don't buy stuff like that to put where it can blow the engine up (e.g. timing belt components) but for stuff like this where I get a lifetime replacement if it pukes again, it won't take out other things if it fails and its reasonably easy to R&R? Sure.

 

[OlyTDI]

HA! I was just looking at that. There's another one made by Four Seasons (undoubtedly another Chinese manufacturer) linked from that page you posted that is $195 with 20% off. So about the same price but has to be shipped in. Sold under Carquest Premium branding. Also lifetime limited warranty. I may just go pick up the Dorman tomorrow. I dislike playing fan Russian roulette. The TYC is Taiwan not mainland China but that didn't seem to matter on mine...

 

[Genesis]

Given the numbers you're posting up for amps I'd swap both. Once I figured out how to get the spider off it took longer to get the belly pan off than to actually change the big one, and I don't think the little one is any tougher.

 

[OlyTDI]

Yep. I changed both last time. Saved the frame just in case. Now, I'll have the beginnings of a fan frame collection! But I have a bypass oil filter setup and a frost heater -- both of which make the swap a lot tighter! But doable -- I've done it before.

When you say your Dorman crapped out in an hour -- in what manner? Seized? Brushes? Resistor?

 

[Genesis]

Low speed failed; high still functioned and there was no evidence of seizure or similar. Best guess: The resistor wasn't firmly mounted against the case, had no heat dissipation and thus burned up almost immediately. Typical C.R.A.P quality control but the replacement (which they handed me over the counter immediately when I took it back; I put it back on the shroud with the other one and returned the set) has been fine.

 

[OlyTDI]

Can't believe that there is such failure variability.

 

[OlyTDI]

An update: I replaced both fans today. They work (so far!) and the AC is working as well. We'll see, over the next few days, if the fuse blowing is resolved. I'm feeling optimistic!

Because I don't have room to remove the entire frame plate with the two fans mounted to it, I have to remove each fan still attached to its three legged mount, then attach the new fans/mounts to the original VW large frame plate that remains in the car. Interestingly, the large fan/mount from the Dorman assembly, was a direct swap. The small fan's three legged frame, however, was a different configuration and would not line up. As such, I had to swap the new Dorman small Fan motor and blades onto the old TYC fan three legged frame from the faulty fan that I removed, then reinstall that in to the large frame plate. No big deal but it was an unexpected development.

The last time I replaced both fans, I used TYC (that also came mounted on a large frame plate) and both fans/mounts were a direct swap off of the frame plate they came mounted on and onto the original VW frame plate in the car. The Dorman set threw a curve ball. Just an FYI if you are swapping fans without pulling the large frame plate to which they attach.

 

[Genesis]

Short video showing what "Low" is like on my ALH from this afternoon....

If yours wasn't like this before that adds a LOT of "probably was" to the equation... was doing an oil change on the old beast this afternoon and shot this just for kicks-n-grins.

Low fan ALH

rumble.com

 

[OlyTDI]

Yeah, when I first tested out the new fans (blower on/AC on/key on/engine off) they seemed just a little bit slower than the previous ones were on low. At least they were a smidge quieter. I think my previous fans were like, slow-and-a-half on slow...

Those are going quite slow on your video...

 

[OlyTDI]

Thought I'd check in and give an update to this fuse blowing issue:

It's been a few weeks now since swapping out both fans with the cheap-o Dorman's ($150 -- lifetime warranty) and I've had no problems with the fuse blowing since.

The take-home message for me on this is that if you've got a problem like I had, it would be far less expensive and costly time-wise to just swap out the fans and move on. In retrospect, that would have been the path of least resistance (pun?)...but that's how we learn; some of us more slowly than others!

 

[P2B]

If the fans were the issue, I would expect you could reproduce the blown fuse by starting the fans repeatedly (using the AC button) without the engine running.

I find it odd you were unable to isolate the issue to the fans with this test - but glad you got it sorted, and thanks for following up!

 

[OlyTDI]

Yeah, little about this made sense. The fuse blowing very well could occur at any time, I guess, but so far, it's stable.

 

[Genesis]

A dropping resistor that shorts produces high current (and a fast-running fan), one that's open produces a non-running fan. The key to the failure is right here:

Each fan had around 0.6 - 1.0 ohms resistance at all positions. Nowhere could I find a spot with very small or no resistance. I did the test for each fan on each pin (so, each pin on each fan = 4 tests) and then did all of that again slowly rotating the other direction (4 more tests).

I could not find anything anomalous. EXCEPT, it seems that when I power the fans directly (using a power probe right at the fan's connector) They run at the same speed regardless of which of the two pins are powered on an individual fan. This occurs on both fans. So powering one pin turns the fan at a particular speed and powering the other turns the fan at that same speed. However, when I do the fan high speed jumper test at the coolant thermo switch (found here: Coolant Fan Testing), I get high speed fan operation that is distinctly higher than low speed.

The reason you got "different" (somewhat, but distinguishable) speeds when you hit the thermo switch is that the current path is different for the two modes; the wiring path in the car is different. That is the "high" path has less resistance in the wiring than the "low" speed does, as it has to carry more current in normal operation.

 

[OlyTDI]

Thank you for writing this, Genesis! I think that this thread in general, and your input specifically, will prove quite useful to others in the future.

Your explanation makes total sense and I likely would not have come to that conclusion on my own!