will 78 amp alternator work with mark 5 electric fan

A

Anonymous

Guest
So i have a brand new 78 amp alternator got for little to nothing.My malibu is a normal low option street car no a/c,basic stereo.I have a mark 5 fan from a lincoln ,is this enough amperage to carry that fan?
 

HP JUNKEY

Dragway Regular
Oct 30, 2008
1,093
1
36
Buffalo.NY
Wire a relay in line with it and you should be fine, The realy will take the initial Amp draw when the fan kicks on. It will also protect the rest of your electrical system if the fan decides to take a crap and start drawing too much Amps due to an internal meltdown. You can buy a complete fan relay kit from Jegs or Summit, or go to your local Radioshack, buy the relay and some wire and wire it up yourself. Here is a link to check out.
http://www.summitracing.com/search/Department/Ignitions-Electrical/Section/Electrical-Wiring/Part-Type/Relays/?Ns=Rank%7cAsc

Here is a basic relay wiring diagram link
http://www.ado13.com/techs/relay.htm
 

gbodystuff

Amateur Racer
Mar 30, 2009
260
0
0
Iowa
I build Mark VIII fan kits for gbodies and I can tell you a cheapo 30-amp relay ain't gonna last long. If you are going to use a relay, go with al least a 60-amp one. I use Hella HD 70 amp relays for mine. And make sure it has a tamping diode internally...this way, you are assured current only flows in one direction-to the fan just in case the relay contatcs ever stick closed. The fans I use-RF64 which is 90 amps at start up for a few milliseconds and 32 amps at full speed will smoke as 30 amp relay and even a 40 amp relay will get pretty darn warm. Use high quality 10 gauge wire for power for relay and fan lead. Your 78 amp alternator will handle it but remember, when amperage goes up, voltage comes down. And when amperage goes up, heat is built up in the wiring. You will notice other things like headlights dimming, heater blowing slightly more slowly, etc. when runnign the fan at full speed. There are a lot of ways to modify the factory vehicle charging system to take better advantage of a higher output alternator but that's for another thread...lol. If you are running stock v-belts, I have a solution for you that will give you a high output alternator for a lot less money than you think and involves only a little re-wiring. Go to a parts store and pick up an alternator for a 1988 Oldsmobile Firenza 4 cyl. It is rated at 90 amps and the serpentien pulley can be swapped out for your v-belt one. And guess what else? It has 12 and 6 clocking so it will directly replace your old alternator (assuming we are dealing with a 305 or 350 engine here). Now, go to the HELP section and grab the CS style alternator pigtail...it'll have three wires-black, white and red. The black one is not used (diesel tach lead), the white splices into your factory brown alt. wire (dash gauge lead) and the big red wire splices into your red lead on your factory alt. wirng. The main charge post wiring goes to battery +12V. Done-90 amps and super easy to do! That's just one of the many little tricks I have for modifying the charging system. The alternator is about $60-70 bucks and the alt. pigtail is about $10.
 

gotcha79

Amateur Racer
Oct 17, 2009
196
0
0
Harvey,IL
just to add i read this somewhere and i was gonna try a 88 caprice alternator its said they too have the same 12&6 oclock mounts but there alt push 140amps. but i might be wrong
 

gbodystuff

Amateur Racer
Mar 30, 2009
260
0
0
Iowa
The stock 88 Caprice is not a 140-amp alternator...it's 105 with 4 and 7 clocking, and you simply cannot get that much current reliably because the 5.25" case cannot shed enough heat. The 6" case ones are 140 amps but you can't use them in place of your v-belts-you can't support the belt tension off the alt. bracket no matter how you try to fit it. I use 140 amp alternator on serpentine conversions only and even with that I had to make heim-ended brackets as a brace to the top of the manifold for support. Trust me, I have tried everything-some things work, others don't. I've even re-wired a Ford 130 amp 6" cased alternator that had 12 and 6 clocking and used that before too on a serpentine conversion-that one always throws people off...lol.
 

gotcha79

Amateur Racer
Oct 17, 2009
196
0
0
Harvey,IL
on note the caprice alternator should work fine but i need to make a small correction its a 87 caprice alt you will need and true its is not 140amp its a 120amp but your mounts still are at 12 and 6 o/clock mount autozone has them for about $120 but theres a bunch of them from in the yards
 

gbodystuff

Amateur Racer
Mar 30, 2009
260
0
0
Iowa
Ahhh...that would make a good swap. I use the later style CS style because the GM (not the cheap aftermarket ones) voltage regulators in those have a much quicker operating window in which they sense an increase in voltage demands and regulate output accordingly. Only GM ones are like this...the cheaper parts store lifetime warranty alternators with all new internals are not as high quality in this regard. That info I learned from Madelectrical over the phone. Years back we talked for about an hour about electrical theory and how the various regulators through the years had changed. He informed me about the window times in GM alternators and how I think he said by 2008 or 2009 (I talked with him prolly 6 years ago at the time) GM hoped to have the window time down to 1/10 of a second or so. Meaning anytime you turn something on, the window time for maintaining system voltage is essentially instantaneouos. He has a ton of knowledge on stuff like this and he is the nicest guy I have ever met in terms of offering advice over the phone....I wholly recommend him if you have specific questions about charging theory. I build custom wire harnesses for my customers on our pro-touring builds and his advice I always keep in mind so if anybody ever wants to know I choose what I do, I always have a reason. GM has always been awesome at interchangeability and that is what makes these kinds of swaps fun!

As a side note...I did some work on my father-in-laws '04 Chevy Silverado and I noticed his 5.3 alternator has the same clocking (and in the same position) as the serpentine swaps we routinely do and the case appears to be 5.25" also. There is three wires coming from the regulator besides the main charge wire and that alternator is rated at 145 amps. It accomplishes this by having a LOT of case venting so it looks like I'll be figuring out the wiring for it and buying one to try it out....it's a pretty heafty alternator that's for sure!
 

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