Alternative Fan Wiring -- A Sanity Check, Please...

[patrickt]

Bob P., I have the heavy duty fan, along with the pusher fans, to keep my FE cool. They all come on at the same time and the initial high amperage pull pegs the ammeter gauge to the left, the needle then sticks there, and I have to rap the gauge with my knuckle to make it come back. It's done this since the day the car was built. A couple of years ago I modified the wiring on the fans. I removed fuse #1 and ran a yellow 12 gauge wire directly from the circuit breaker to the driver's side of that fuse housing, thus bypassing the ammeter for the fan circuit (I leave the original fuse for the fan circuit out). I installed a plastic in-line 30 amp fuse on the yellow wire. Here's a picture:



That seemed to work very well. Since the fans were no longer being fed through the ammeter, the pegging of the needle problem was gone. Plus, it gave me the added benefit of telling me exactly when the fans were running because the ammeter would show a moderate charge condition if the fans ere running. I really liked this, because you generally can't hear the fans over the FE. The ammeter needle was either straight up and down, or kicked moderately to the plus when the fans were on; very convenient and very handy. Much better than a little light that some have wired in to the fan circuit because it shows the actual load of the fans running, as opposed to the little light that only shows the fan circuit is energized (a break at the last leg of the circuit, right before the fans, would still have the little light comeone, but the fans would not be running, and yes I've had a break there -- a break at the very end of the circuit wouldn't fool the ammeter, though, because there is no corresponding load).

This worked well for the last couple to three years... until yesterday. I was out in the Cobra and came upon a bit of slow moving traffic. After sitting in line for a couple of minutes I glanced down at my ammeter gauge expecting to see my "moderate charge." Instead, the needle was straight up and down, telling me, of course, that my fans were not running. My temperature was just under 90 degrees. I threw the manual fan override switch on and the ammeter needle did not move a bit -- I was now over 90 degrees; I knew I didn't have much time. I was able to make a turn down a side road, get some air flow through the radiator, then shut her down and open the hood before she overheated. Here's a picture of my inline fuse, which was the culprit:



Now mind you the FUSE DID NOT BLOW in that plastic fuse holder -- it was still as good as new. Rather, there must have been a little bit of oxidation that formed on the spring connector, which caused a poor connection where it touched the fuse. This caused the heat to melt the plastic thus breaking the circuit. The heavy amperage draw of the fans coming on/off, on/off, on/off no doubt helped contribute to the fuse assembly's failure. I made a quick repair by the side of the road and headed back home. I like my setup, but obviously I'm not going to use another plastic spring fed fuse holder. I was thinking instead of using a nine inch 18 gauge fusible link, butt-spliced in where I had had the plastic fuse.

What do you think of the idea of the 18 gauge fusible link, and I might as well get a sanity check on my whole wiring setup, too. So please tell me what you think, I'll even listen to ERAChas as well.

[Excaliber]

What do you think the 18g amp rating will be?

[patrickt]

Originally Posted by Excaliber

What do you think the 18g amp rating will be?

Well the rule that I have always heard is that you use a fusible link that is four gauges above the circuit gauge. I think the wires running the fan circuit are 14, so an 18 gauge Fusible Link would make sense. FLs really are not rated on amps, I don't think.

[Excaliber]

Yeah the pics are good. I see you have a heater, I just recently installed mine and have yet to run the water hoses.

[ERA Chas]

Originally Posted by patrickt

I'll even listen to ERAChas as well.

I'm sorry Patrick, I'm less expert in the theorems of Edison and as you know extremely expert in the teachings of Pythagoras and Iskenderian.

Besides you asked Bob first...

[patrickt]

Originally Posted by Excaliber

I see you have a heater, I just recently installed mine and have yet to run the water hoses.

That probably bought me the extra couple of minutes that kept me from overheating. Seriously, my fans pretty much don't run if I'm moving at anything over a crawl. The car runs pretty cool; even in extended stop and go traffic on a humid 100 degree day it still stays in the high 80's. I also have the extra venting through the wheel wells and the heat-sheilding around the primaries. That, along with ceramic coating the primaries, makes a big difference.

[Jerry Clayton]

Patrick

I guess you know by now that what you thought was a spring in your fuse holder is really a heating element in disquise---

And you might be going 4 numbers the wrong way when fiquring your wire guages!!!!

Why don't you put the Lincoln Mk8 fan in the car???pull too many amps???

If all else fails--remember that the number of amps your fan pulls tells you how much it contributes to an change of energy (cooling air flow)

Jerry

[patrickt]

Originally Posted by Jerry Clayton

I guess you know by now that what you thought was a spring in your fuse holder is really a heating element in disquise---

And you might be going 4 numbers the wrong way when fiquring your wire guages!!!!

Why don't you put the Lincoln Mk8 fan in the car???pull too many amps???

The "add four gauge" rule is the way you do it with Fusible Links -- I just read a couple of articles on that. Some of them also encourage the use of FLs for fans because of the high initial draw when they come on. Coupled with the fact that they are going on and off all the time they tend to wear out fuse holders (like what I was using). Aside from that, my cooling system works beautifully. It would seem that a FL would be the perfect solution. Sooner or later Bob P. will quit sunning himself in the backyard and post an answer....

[strictlypersonl]

I don't have enough (read that zero) experience with fusible links to comment on those, but have you considered a blade-type fuse holder? You should be able to grease that design up without any fear of losing good contact.

[patrickt]

Originally Posted by strictlypersonl

I don't have enough (read that zero) experience with fusible links to comment on those, but have you considered a blade-type fuse holder? You should be able to grease that design up without any fear of losing good contact.

Yep, that's one idea. Here's an interesting little post about Fusible Links and fan circuits. http://www.alanhorvath.com/54chevy/fusible_links.php

[tcrist]

I really do not have any information to help but I do have a question though. Has anyone added (or is there even a) re-setable breaker that can be used rather than fuses?

Is there any practicality in even having them?

[patrickt]

Originally Posted by tcrist

I really do not have any information to help but I do have a question though. Has anyone added (or is there even a) re-setable breaker that can be used rather than fuses?

Is there any practicality in even having them?

Yes, you'll see in my picture that the yellow wire goes to an automatic circuit breaker that protects the entire wiring system.

[Jerry Clayton]

looking at your pic of your firewall shows that your wiring scheme is completely flawed---

It is pretty obvious that you don't understand---

[patrickt]

Originally Posted by Jerry Clayton

It is pretty obvious that you don't understand---

OK, do you know when a fusible link should and should not be used?

[strictlypersonl]

I like the circuit breaker idea. I only stock 50A and 75A ones though, and you should probably stick with a 30A value. Waytek's got them in both stud and blade designs. I have to put in an order next week, so if you can wait a while...

[tcrist]

Originally Posted by patrickt

Yes, you'll see in my picture that the yellow wire goes to an automatic circuit breaker that protects the entire wiring system.

Is that the little 2 post one on the left end of the wire?

[patrickt]

Originally Posted by tcrist

Is that the little 2 post one on the left end of the wire?

Yes, they're very handy. That's a 50 amp one, if I recall, and sits between the battery and the entire wiring harness (except the full dump to the starter motor). Remember, most of the time there's very little current crossing it, even if you have your fans, lights, wipers, turn signals, and horn all going off at the same time. None of that draw would pass through the circuit breaker, unless the engine wasn't running. They don't cost hardly anything. Click here: http://www.wiringproducts.com/contents/en-us/d60.html

Originally Posted by strictlypersonl

I like the circuit breaker idea. I only stock 50A and 75A ones though, and you should probably stick with a 30A value. Waytek's got them in both stud and blade designs. I have to put in an order next week, so if you can wait a while...

No worries; I might even have one down stairs in the basement. I usually take your advice.

[MFE III]

Patrick, I don't think it's a good idea to have your pusher fans wired into your thermo switch along with your puller fans. Since the 2 fans move air at different rates, I think you can create turbulence between the two - which is your radiator- and actually detract from the efficiency of the puller fan. I have my pusher fans on a manual switch and really only view them as decoration. Many don't even wire them in and just let them spin from flowing air.
Besides, taking your pusher fans off the thermo switch will cut down on the big draw you have when the thermo switch initially opens.
Just my dos centavos!
Matt

[patrickt]

Matt -- you're probably right. I just love the look of the pushers when they're spinning. But you know, when the car's moving they're probably spinning anyway even when they're not getting power.

[patrickt]

Originally Posted by strictlypersonl

I like the circuit breaker idea. ...and you should probably stick with a 30A value.

Done. But in tribute to the the car's British roots, you'll note that I have mounted the 30A circuit breaker on a "jaunty angle."