I live in Southern California, I have a 1978 L-82 and I have just installed a DeWitts aluminum radiator as well as dual SPAL electric fans. The car has an original Delco Remy alternator (63 amp?) and basic stereo with a small amp. All else is original. I have several questions:
1) I am looking for some feedback on pulling the power for the fans from the starter vs the battery as is suggested by SPAL?
2) Should I upgrade the alternator to 100, 140 amps? I am also thinking of running it on the current alternator and upgrading the alternator if and when necessary. (alternator is probably 20 years old)
I'll open this by saying I'm not a mechanic so my experience is limited to my own vehicles which would be minibikes, motorcycles, and a range of cars from a '32 Ford roadster to various family vehicles and my '80 L82. Then I'll couple that with being an ME and working for a company that makes mostly electrical connectors. In a nutshell, advice is worth the price charged
The first question is what is the current draw on the fans. I looked for something on this, and the first one I came across said 30 amps. 30 amps at 12 volts is 360 watts which is about 0.5 hp. There seems to be a big debate over just how much hp a mechanical fan takes, but it's all in the range of a few hp, so I don't doubt that the fans when running will need tens of amps.
The original alternator in the car was something like 65 amps. If you are still using the original, i.e. never replaced - never rebuilt, then it will be producing significantly less than this. This I can say for sure since in getting my '80 up and running again recently, the choke light kept coming on which indicates it has too little voltage. A new alternator fixed that. End of experience based car knowledge and now on to somewhat informed speculation.
Since the fans will draw at least 50% of the current the original alternator can put out and since the selection of the original alternator capacity by the engineers at GM was based on what the car as built required with maybe 30% margin, that alone would say you need a bigger alternator. My recommendation would be add whatever the spec current draw of the fans is to the original alternator to decide how much capacity you want in the new one.
As for whether to bolt direct to the battery or make life easy by going to the starter, I think the issue here is that if you go to the starter you may add some resistance to the system. Basically the system resistance will be the wire from the bat to starter plus the wire from the starter to the fan plus the connection between the starter wire and fan wire. Note this last one is more important than people realize - per my first paragraph, I work for a company that makes electrical connectors, so this is advice worth something). On the plus side, since the fan harness won't run all the way to battery, having it shorter may save some resistance. The concern with the extra resistance will be you will have a lower voltage drop across the fan as some of the voltage will be used pushing the current through the extra wire and the connection. You could compensate on the wire side by using a larger gage. One jump in gage, say from 12 AWG to 10 AWG will give you about 60% more cross section which is probably enough to manage any difference with the extra length.
The tricky part may be how you connect the fan wire to the starter. Starters have a very large current draw. And the connector on the fan is unlikely to be designed to carry that level of current. So you need to place it in a way that prevents the starting current from passing through the connector on the fan harness. The question here is does current get to the starter by passing from the cable to the nut holding it on to the cable and then through the stud or does it get to starter by passing from the cable to whatever it rests on at the base of the stud. I've never looked at that.
for what its worth, most,if not all of the power to the cab of the car is taken off the wire going to the starter(usually spliced by a fusible link, there is only one wire off the battery that goes to the starter, and at the starter there are a couple others that feed the rest of the car) but you'll also notice all the dash gauges and radio are cut off while starting, those are usually tapped off the starter solenoid so when starting it kills that portion of the circuit of voltage... and, while the starter, when activated, will draw hundreds of amps(150 to 300+) if you have your headlights on(they are feed constant), you'll notice they will dim, but not blow from the amperage being drawn by the starter... the voltage however, will drop with the starter(depending on how "heavy" your battery is, voltage could drop to 10 volts while turning over the engine).
Personally, if i could, i would wire up the fans through the fuse block on the Key On side of the fuse block, so with the key on, the fans will run, BUT it shouldn't with the key being in the starter position...or if you are not forgetful like myself, wire it up to a constant hot with a heavy duty switch so you could run the fan with the motor off to help cool it down faster but if you forget to turn it on, overheating will occur, and if you forget to turn it off dead battery will occur... trust me on that one, don't ask........
and i will agree the alternator should eventually be upgraded to a little higher amperage, but nothing extreme... 80 amps or so... once you get up in the higher amps, 110 or so, the battery doesn't hold up all that well.... former Boss's Chevy Suburban(130 amp alternator) would burn up a battery after a couple years(fortunately we were a battery distributor ;) ) and now that i think of it, your lights will draw about 30 amps, and so will your heater/ac fan.. if those are running at the same time, you are already nearing the max of the alternator)
StingrayJim NCM Lifetime Member #1936
Stingray's '76 StingrayJr's '78 Lil Red '94 (click each one to see a bigger version)
On the issue of controlling when the fan runs, I assume the fan has a temperature switch to control when it runs. The original electric fan in my '80 does. I would think it is just a normal control on any electric fan and would would alleviate any worry about having the fan on when starting or accidentally leaving it on and draining the battery. If tied directly to the battery it would also ensure that the fan would come on with the key off if needed which is sometimes the case if as the coolant in the engine block will continue to heat up after the car is shut down. In fact, the only time I ever heard my electric fan come on was after some particularly hard driving and then an immediate shut down. The electric fan kicked in about a minute later. It had to do with avoiding a discussion with local authorities one night many decades ago. Let's leave it at that.
Rut-roh Vince . True about the fan with a thermostat... if it comes with one, or if you add one... I know the one i put on did not come with a thermostat, however, i just wired mine straight with a key on hot wire.... given that these cars tend to run a little warmer than, say a dodge pick-up(due to the air flow from the grill) and that i am here in the south where summer temps tend to get on up there(plus the humidity)... i chose to run mine that way your milage may vary :)
StingrayJim NCM Lifetime Member #1936
Stingray's '76 StingrayJr's '78 Lil Red '94 (click each one to see a bigger version)
Interesting that the aftermarket ones don't come with a thermostat control. I guess that's because they are assumed to be primary cooling vs the 80's which were supplemental. Concerning heat and humidity, my vette actually started out in TX where I bought it new. I was living there working in oil field engineering. So it did see a lot of the summer heat and humidity on the gulf coast. Never once though did the that electric fan kick in. Only did it at night in NY per the earlier comment. In fact, at one time I drove the vette for over a year with a radiator leak that prevented it from ever being more than 2/3 full. Never had a problem with over heating. Originally the vette did not come with its rubber air dam under the front spoiler. The dealer, Atzenhoffer in Victoria apparently never put it on and I didn't realize it was supposed to have one until a couple years later. To their credit, when I notified them about it they sent one to me 5 or 6 years after I bought the car. Believe it or not, adding that 1.5 inch strip of rubber deflected so much more air up to the radiator it ran 20 deg cooler. So while the front grill size is a limiting factor, a little clever aerodynamics work can work wonders to get air flow diverted to where it's needed.
First, thank you for the replies and sharing of information. Before I get into an update and primarily for the benefit of others that might be reading this, I'd like to expand a little bit on how I ended up completely updating the cooling system.
About a year ago, I realized the right front caliper was leaking. As I attempted to loosen the brake line, it twisted to the point that I had to replace it. So, as you would expect, to get better access to the brake line, I removed the fan as well as radiator hoses. It was at this point, after evaluating the condition of the radiator, that I decided to eliminate the long-standing issue of the car running hot and/or overheating. Side note, as for the timeline of one year, it should be noted that, through the use of this Forum as well as in addition to a couple of YouTube videos, I rebuilt the front headlight actuators (both were lazy) for a lot less than replacing them.
As for the cooling system update, in addition to the DeWitt's aluminum radiator with dual spalfans, I installed a Stuart high volume water pump, a Robertshaw hi flow thermostat as well as replaced all radiator and heater line hoses. The thermostat is a 165 and while the upgrade only came with one temperature sensor, I installed two temperature sensors, one for each fan. The first is a 185° sensor (off at 170, I believe) of which is installed on the radiator directly below the upper outflow Outlet. The second is a 195° sensor (off at 180) of which is installed on the top of the thermostat housing.
As for the wiring, I wired and connected both fans to the starter with fittings such that they are right on top of the main power feed. I then wired the gray (Spal) ignition line directly to the ignition plug directly at the fuse box. Then, last night, I fired the car up. And while I haven't taken it on the road I have to say, everything went well. The car heat it up nicely and almost to the degree (as displayed in the car on the temperature guage), the first fan kicked on at 180 at which time the temperature started to drop almost immediately. While still idling, the fan kicked off a couple of minutes later. All electrical seemed to be working fine with the original Delco alternator. Actually, regarding the alternative, just to be clear, it is not the original as much as what I believe I replaced years ago to match the original. T
That all being said, the true test will be how the the car runs on the road and I'm curious to see where the "average" temperature will sit with both fans. The fact is that I can change the thermostats and the sensors to whatever will work best. One other consideration I have is to install some software/hardware that I've read about (in this forum) that can gradually start up and stop the fans as opposed to just on and off.
Additionally, as a result of having the front end apart, upon putting everything back together I realize that the vacuum lines needed to be replaced as well as the charcoal canister configuration might have been out of whack and or disconnected. Thanks again to c3vr for its resources as I did quickly educate myself on the function and layouts of the vacuum lines. Honestly, the car ran better when I started it then it did a year ago.
Thanks again for the feedback and I will be sure to update with what I end up doing regarding the alternator of which I now understand bigger (more amps) isn't necessarily better.
P.s. I also did rebuild both front SS calipers where by I upgraded to the newer o rings.
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