cooling fan

[ironhead]

I have a CR with a 460 crate, 560 hp. It has a Flex A Lite Black Magic M150 cooling fan. Standard CR wiring. When the fan kicks on, the volt meter drops from 12 1/2 , 13 down to about 8 and wont start. I sure could use some ideas if anyone has had this problem. The motor and fan only have 2000 mi. On them. Thanks for help

[RICK LAKE]

iron head 3 problems, Lets start with charging system, How big is the Alt in amps? How many curcuits are pulling power when the car is running? Lights, electric fuel pump,Ignition box, ECU for FI system? If this happens at idle the Alt can't keep up with the load on the system. I am going to say that the battery is new and fully charged. It doesn't hurt to pull it and go and have it tested for loads and CCA rating. You could have a bad cell. Car will start and run but with things on like cooling fans they pull about 10-20 amps. At idle the charging system can't charge the battery. Ideas charging for a battery in voltage is 13.7-14.2 volts. As long as you are 12.7 volts and holding with all drains on you are ok. Anything less need to rework the system, see below.
3 possible fixes
1 Does your motor have March pulleys on it and are they underdriven? If YES need to go. The Alt is not spinning fast enough to keep both the battery and load getting enough ampage to system. The water pump and crankshaft pulley should be the same diameter. As for the ATL pulley size should have the stock pulley on it for a loaded opitioned truck or car. If not change pulleys first. If you have alot of curcuits running at idle, the battery will discharge trying to keep power going to every curcuit.
2 Output of Alt, in the old days we had only a couple of curcuits in a cobra. 37-42amp Alt was fine for this car. Today, multi fans, electrical fuel pumps, Ignition boxes, Better head lights, Stereos, and other power drainers. Need a higher power Alt in the 90+ ampage for the car to start everything and handle all the loads at idle. There should be a number on the ALT that said --amps. We are looking for 80 or higher. The Alt can be pulled and tested for output also. One of the diodes could be burnt out and cause a weak output on the ALT. OUtput should be within 5% of number on case. Less buy a new rebuilt Alt. There is a PROBLEM with running more than 70 amp ALT's. The Amp meter in the dash Can't handle this load over long periods of time. There are other threads about amp meters burning up dash harnesses, melting the insolators on the gauge and other problems. IF you are going with a higher output Alt than 60 amps, replace the Amp gauge with a voltage gauge. Works almost the same and you can chack the output of the charging system looking at the gauge. A simple rewiring from amp to volt is done. Will need to add a 125 fusible link to the output on the Alt for protection of the car incase of a short or rub through on the power side.
3 There could be something going bad with the coolant fan(s). Need to find out how much ampage they are drawing. When the fans kick on there is a ampage and voltage drop for a second. The gauge could pin and bounce back with them running. Other thing is a bad relay for the fans. These are easy to replace and might help lessen the spike load.
The bad thing with a cobra having a amp gauge all the loads go through it. There are only 2 terminal post and small nuts that handle this load. under 60 amps total no problems, over 60 amps, looking for a melt down over time. Either way replace this gauge. This should give you all the info you need to fix the charging system.
A place called PA preformance sells a complete kit to swap out to a bigger Alt leaves the voltage box and looks orginial in the car. This kit works great. I have it on my car as well as going to a voltage gauge. Good luck with problem. I think you will fix it. Rick L.

[ironhead]

Rick, thanks so much for your reply. Electrical is not my strong suit as you have guessed, but I will try to address each item you mentioned. My CR wiring might be a bit light at 14 ga from the fact. I had the 70 amp. alt. tested at Advance Auto, but they couldn't tell me what it put out, just that it works, which I knew. I have March pulleys, crank 6 1/4 in. Water pump 5 in. Alt. 3 in. Serpintine belt. MSD 6AL ign box. Optima 800cca 1000mca battery. My problems occur after the engine has warmed up and the fan kicks on the voltage drops from 12 1/2-13 down to 8 with only the fuel pump and fan on. A s you can imagine the car doesn't get driven much, 1500 mi. since completion in '90s. Thanks again Rick for your input.

[Detroit Bill]

I would check all the grounds first and clean the battery terminals. Then dig deeper. Start with the simple stuff.

[ironhead]

Thanks Bill, I've run a heavy ground from the trunk mount battery up to the starter mounting bolt and engine side of the motor mount to the chassis. Battery terminals are clean. Thanks for your input Bill.

[C5GTO]

I have a 100 amp alt in my CR and it barely keeps up with the draw. Does OK with the cooling fan on at an idle but if I turn the head lights on, it drops to 12v or below. If I tried to get by with a standard 75 amp alt, I'd be in trouble.

So it's just marginal with 100 amp but I have a 5.0 EFI motor with electric fuel pump and 17" cooling fan. It's a good thing I don't drive the car much at night. In addition, the older Ford alts don't put out much of their capacity at idle. You'll need to use a newer alt for that. My alt guy recommends a newer, compact GM 1 wire. He says these put out more amps at idle than the old Ford alts but you'll need to have it re-clocked to fit in the customary position in front of the passenger side head.

I hope that helps...

[DAVID GAGNARD]

Originally Posted by ironhead

Rick, thanks so much for your reply. Electrical is not my strong suit as you have guessed, but I will try to address each item you mentioned. My CR wiring might be a bit light at 14 ga from the fact. I had the 70 amp. alt. tested at Advance Auto, but they couldn't tell me what it put out, just that it works, which I knew. I have March pulleys, crank 6 1/4 in. Water pump 5 in. Alt. 3 in. Serpintine belt. MSD 6AL ign box. Optima 800cca 1000mca battery. My problems occur after the engine has warmed up and the fan kicks on the voltage drops from 12 1/2-13 down to 8 with only the fuel pump and fan on. A s you can imagine the car doesn't get driven much, 1500 mi. since completion in '90s. Thanks again Rick for your input.

For comparison on my 65 Mustang Fastback,I'm running the same size pulleys as you, I don't think the pulley size is your problem....I also run as full MSD ignition and a 19" diameter 2 speed electric fan off an early 2000 model Cadillac something or other I got at a local body shop.... I have it wired on high,never had the low speed even hooked up...Not sure of it's amp draw,but it is substantial.....along with all the other things electrical found a 65 Mustang (headlights/heater blower motor/windshield wipers/am/fm/cassette radio).....
I have the old style Ford 60 amp alternator,19.95 Auto Zone reman. special that is no less than 15 years old,I did convert it to one wire to eliminate the wiring and old style voltage regulator......Optima red top battery......

At idle with nothing on other than the car running,volt gauge reads between 13.5 and 14 volts,with the fan on volts drop to 12.5 to 13 at idle.....turn on the headlights and wipers and the volt gauge never goes below 12 volts and this is at 900 rpm idle......on the road volt gauge will be around 12.5 or a little better with everything on.....

Now back to the fan.....I have it wired with a heavy gauge wire from the alternator side of the starter solenoid and into a relay....when wiring anything with a draw like an electric fan, you need to use heavy gauge wires AND a relay..........

Your amp rating should be enough,I would drive it over to a dedicated alternator shop and have them check your amp draw with various things on and check the alternator amp output, that would tell you a lot more....your alternator could be putting out 13.5+ volts but with a bad or dead diode,your amp output would be less than the alternator is rated for......also they need to check your voltage regulator at the same time..........could easily be one or both causing your problem and being your volts drop to 8, I'm betting both!!!!!!!!

I think you'll find the problem in the wiring and the alternator amp output as a 70 amp alternator should be more than enough to keep up with the draw you have.....

David

[RICK LAKE]

Ironhead Was the battery tested and fully charged? I personally are not a fan of Optima batterys. Design is great for every where to mount it. Have had failures of them in higher vibration conditions. Lets test the battery with a full charge. If you have a head light and to wires, run the light of 60 seconds to take the top charge off the battery and test.
I can't under stand why they can't give you a full charging reading for the Alt. It could still be bad and breaking down once it warms up.
Wiring of the fans shoudl be in 12 gauge with heavy duty relays and using high speed only.
Is the heavy discharge happening at idle only? What is the idle on the motor?
If we raise it 100-200 rpms can the charging system handle the load? If yes, we may just need to get a smaller pulley on the Alt to increase thw speed of the Alt and keep everything charged. If not, and this was my car, I'm going to a 90+ amp Alt. Most cars and trucks on the street have over 100 amps now. The wiring is lighter in gauge because they removed the 10% fudge factor in safety of the trucks and cars. Saves money on copper which scraps for about $3.00 per pound.
Lets stay basic, check battery and test. After this we check rpm range with fans on and where the charging system can handle and charge all the normal loads on the system. Do this and come back with the answers and lets see wear this goes. My main concern is the AMP gauge, I have burnt off the insolators on this gauge with too much current going through it. I was running a 70A ALt with the orginal ALT from Ford. Over time the system could not handle the loads with being safe and almost cooked the dash and harness. You don't want to let the smoke out of any curcuit.
I will look at the March setup and see what the under and over drive ratios they have. I got a set of March pulleys for my FE motor and they where 20% underdrive and cause alot of problems.
Talk to you soon Rick L. Ps after we get this fixed we need to look at the curcuits for the fans and go to a larger wiring and 40 amp relays to protect the car over time.

[ironhead]

Thanks to all responding to my postl In response to Rick's comments, I checked the battery as you said, and it showed 12 volts. I called a "pro" alternator shop who said he could test the alt., drove 25 mi. Each way to find out it puts out 14 volts, but was told he might ruin the built in voltage reg. If he ran a amp. test. Go figure To answer some of your guestions, no amp ga., just voltage.Low charge at all rpms once fan comes on. Idle is 890-910 rpm. I think I need to get a 100 amp alt. from Jeg's or someone, smaller alt pulley. I think I need to bypass CR wiring completely due to 14 ga. Problem is where do I get a good keyed power source . Some have said the battery side of the starter solenoid, or the alt terminal, but they are always keyed.------right? What about manual overide switch? 10 ga./40 amp relay?

[DAVID GAGNARD]

I converted my old Ford alternator to a one wire type,not anywhere near my car,but best I remember, the alternator output is connected to the battery side of the starter solenoid,not 100% sure but maybe 8 gauge wire,I know it's pretty good size......on my other computer I have a wire size chart I can post but that will not be until Friday before I can get to it and my car to verify......

If my memory is right(???), big gauge wire from the alternator side of the starter solenoid to the relay, then from the relay to the fan,again big gauge wire.....I have a toggle switch under the lip of the dash to turn on the electric fan,it is wired manually only....just the way I wanted it....... I tied into the toggle switch with a "standard" size hot wire from under the dash as it only carries 12 volts to engage the relay,so no big wire is needed..........it works and works well and has been wired this way for at least 15 years.......

Wish I had the wire chart handy, it shows the size of the wire and the length and how much amperage that size wire,that length carry safely handle,very informative........
the other thing is anything pulling the amount of amps electric fans pull needs to be wire on a relay and not just straight wires/switches, they can't handle the amperage/heat for very long before they melt and/or short out...

BTW: the only time I need to use the electric fan is in city driving, anything over 35 mph or so on the road, I have enough air flow thru the radiator to keep the engine temp at 180.........

David

[C5GTO]

I bought my SPAL cooling fan and wiring kit from these guys: Home | The-Fan-Man spal fan manufacturers, electric automotive cooling fans

You can buy the wiring kit/relay separately. Good prices and you can get the relay pre-wired with the proper wire sizes and fuse. I wired my cooling fan power source directly to the battery cable side of starter solenoid. So by-passed all the CR wiring harness for this and it works great.

You can buy 100 amp Ford alts from Summit, Jegs, etc. They work OK but you'll get something with cheap bearings (not US made bearings).

If you're spending the money for a new alt, I'd suggest you go to your local alt shop and have them make you a compact GM 1 wire alt clocked so it will mount on your Ford motor. I believe you can get these in 110 amp or maybe even 120. It never hurts to have extra output capacity! These alts put out quite a few more amps at 900 rpm than the old Ford alts do. That's when you'll need it because the cooling fan invariably comes on when you're sitting at the stop lights.

[ironhead]

Thanks Joel, I like your Cobra pics. I will follow up on your advice.This has been an ongoing problem, I would like to enjoy the car. I think CR's wiring is way to light.

[C5GTO]

Originally Posted by ironhead

Thanks Joel, I like your Cobra pics. I will follow up on your advice.This has been an ongoing problem, I would like to enjoy the car. I think CR's wiring is way to light.

Thanks for the compliment. My CR has 35K miles on it now, is my commuter car and looks better in pics than up close

There's an additional thing you could do if you have the battery in the trunk, are using a gear reduction starter, and have a heavy gauge positive battery cable. I'd do all the other stuff first though.

I had all the above in my CR and my auto elec/alt guy advised me to swap the "0" gauge sized battery cable for a 2 gauge. His explanation was that there's amperage loss as the electrons travel through the copper. With a long run of large cable, there's a lot of copper between the alt and battery so the loss is greater than with a forward mounted battery. With the old fashion starters and a high compression motor, the larger cable was needed. With a gear reduction starter it isn't as they take much less amps to energize and crank. Gear reduction starters use a fraction of the amps as the old direct drives do. He told me I likely could go with smaller than 2 gauge but using that size would always get plenty of power to starter.

After I installed the 2 gauge cable, the system voltage generally runs higher. I've never tried to measure the amp difference at the battery end but the system goes below 12 volts a lot less than it used to. So my alt output is still marginal, just less marginal. As soon as my current alt has a hiccup, I'll fork out the money for a new GM 1 wire alt

I hope this helps.

[ironhead]

Joel, I do have a gear reduction starter and am running #4 cable to bat. I'm not sure what you mean by "clocking". Is that mounting lug oriention, rotation, or what? What vintage or application GM starter would you advise? Not sure if I can find a local shop with the technology you mentioned, Lol GM is the better starting point? I might have to resort to Summit or Jeg's etc. Again thanks Chuck S.

[ironhead]

Joel thanks for the info. I do have a gear reduction starter and #4 cables to the front. Is the 1 wire GM alt. The way to go? What vintage? I'm not sure I can find a shop around here that would know how to boost the output, might have to resort to Summit, Jegs etc. What do you mean by "clock" rotation, bracket orientation or what? Thanks again, were gaining on it! Chuck S.

[C5GTO]

Originally Posted by ironhead

Joel, I do have a gear reduction starter and am running #4 cable to bat. I'm not sure what you mean by "clocking". Is that mounting lug oriention, rotation, or what? What vintage or application GM starter would you advise? Not sure if I can find a local shop with the technology you mentioned, Lol GM is the better starting point? I might have to resort to Summit or Jeg's etc. Again thanks Chuck S.

So it sounds like you already have the smaller battery cable, so you should be good there.

By clocking, I'm referring to getting the mounting lugs and tension bolt in the locations that are needed for mounting on a Ford engine. In addition, having the pigtail/wiring come out in a location that's accessible and doesn't rub on something hot like a header. I'm guessing you are using a V belt where the alt needs to move for belt adjustment. On Chevy's the alts were typically mounted high with tensioner on top. On Ford's the alt was typically down lower (front of the head) and tensioner on bottom. Ford and Chevy engines have same rotation so that's not an issue.

I found this info by Googling "gm late model alternator":

The first GM 10DN alternator appeared on the '63 Corvette and used a remote-mounted voltage regulator. These alternators were rated around 40 amps and are prime material for an upgrade. The 10 and 12 SI alternators were the second-generation units and are generally the same size with similar mounting bosses. SI is an acronym for systems integrated because the voltage regulator was moved inside the alternator. GM built millions of these units from the '70s until the CS130 debuted in 1986. The CS (charging system) alternators offered a generous increase in idle amperage output (generally around 80 amps) with maximum output around 100 to 105 amps. This is an important point. Early alternators required high rpm to achieve maximum output, while late-model versions can achieve 90 percent of maximum output at idle. The CS121, CS130, and CS144 numbers refer to Stator diameters as measured in millimeters. The most popular are the CS130 alternators with a case diameter of 5.12 inches. The CS130D is also slightly larger than the CS130, but the mounting lugs are the same. As case diameter increases, this creates more room for additional wiring and larger rotors, which increase output. Because the CS144 is larger (5.9 inches), it is capable of roughly 140 amps of max output. Keep in mind that as output capacity increases, so does heat. Another little-known fact is that the integral fans pull air through the alternator from the rear and exit the front. This means keeping the rear of the alternator free of obstructions will improve alternator life.

Read more: Alternator Upgrades - Junkyard Builder - Car Craft Magazine

I think the CS130 or CS130D are about the same size as the Ford alt. Hopefully this points you in the right direction.

[DAVID GAGNARD]

found the wire size chart..........this is a really good read with a lot of info......

Charge Wires

David

[DAVID GAGNARD]

Yesterday afternoon was in the my shop with one of my many projects,had not used my car in a while,so decided to start up the car and let it run a while, this is what I noticed.......

Start up,nothing on but the engine running,MSD ignition,volt gauge just under 14 volts....

after the temp got to 180,kicked on the electric fan, volt gauge dropped a little,still way above 13 volts....

for the heck of it,turned on the headlights on high beam,turned on the heater blower motor on high,only thing not on was the W/S wipers and radio....
volt gauge needle was just to the right of 13 volts.....

no matter what was on, it never got to 13 volts, always a tad over 13 volts.......

all this at 900 rpm idle....... and with a 15+ year old Ford 60 amp old style alternator.....


David

[ironhead]

David, I have a GM style 140 amp alt. On the way. I will run a 6 ga. Wire from the alt. to the bat. side of the solenoid, then to a 40 amp relay, toggle switch, then fan. I would still prefer to have the fan come on auto.with temp since I once forgot to turn it on, if I can find a keyed source for power. Maybe my problem is just alt.and wire to solenoid From what you told me about your car, my fan might be my problem, one thing at a time. Like they say, you can't fix stupid,

[DAVID GAGNARD]

Originally Posted by ironhead

David, I have a GM style 140 amp alt. On the way. I will run a 6 ga. Wire from the alt. to the bat. side of the solenoid, then to a 40 amp relay, toggle switch, then fan. I would still prefer to have the fan come on auto.with temp since I once forgot to turn it on, if I can find a keyed source for power. Maybe my problem is just alt.and wire to solenoid From what you told me about your car, my fan might be my problem, one thing at a time. Like they say, you can't fix stupid,

Hey, nothing stupid there, we've all been there/done that at one time or another.........I could write a book on all the bonehead things I've tried and/or done!!!!!
I think the heavier wiring and relay will solve your problem,the extra amps on the GM alternator surely can't hurt either.....

David