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Voltage drop

mobileortho

mobileortho

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I'm running a mark electric fan from a Lincoln mark vii set to kick in at 180 deg. Noticing that there's a considerable voltage drop when it switches on, from about 13 to 11, when the lights are on its only about 10. Any solutions besides using a flex fan?
 
It's a 3 wire. I used this diagram to wire it up.
 

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I'm not familiar with that alternator/plug. Next question is what type of alternator and where do the B and D wires connect to?
 
Looks like a CS130 alternator.

I'll be more specific:

Where does the B wire attach to the truck's electrical system?

Where does the D wire attach to the truck's electrical system?
 
B jumped to the alternator post, D to the ignition. But, I think I may have solved the problem, forgot to install a relay (yeah, having a senior moment)! Went out & bought one from Advance Auto. Hooked it up and that helped quite a bit. Problem is I don't think it a very good unit as it gets extremely hot & keeps blowing the fuse. Everything's wired per instructions, went back & read the reviews & they weren't that great. Gonna take it back for a refund and find a better one. Any suggestions?
 
The "B" jumped to the alternator output post is also a problem. B is the voltage sense back into the alternator. Right now it is sensing (and causing the system to regulate to) the output of the alternator. You need to disconnect it from the alternator output and connect it to somewhere deep inside the electrical system. Any hot point on the fuse box is best. That way the regulator will be "seeing" system voltage, not output voltage of the alternator.

Bilbo was at my house last week helping me get ready for seat belts on my '52. He complained that his '50 (12 volt using a 3 wire 10SI alternator) was measuring about 11.5 volts under the dash when the A/C and lights were on. His truck was wired like yours, with the sense wire connected directly to the alternator output. We temporarily removed the sense wire from the alternator output and hooked it to a hot point in the fuse box. The 11.5 volts immediately jumped to 13 volts with this simple change.

Give it a try.
 
All this smoke I've been blowing has made me decide to change the 1 wire alternator that the previous owner had installed in my '52 GMC with a proper 3 wire system that I've been advocating.

But I'm cheap. So instead of replacing the complete alternator ( $30 - $70 at FLAPS ) I bought a replacement 3 wire regulator ( as low as $3.37 + $7 shipping on eBay ), about $15 at FLAPS. I opened up my 10SI alternator, removed the old regulator, installed the new one, dabbed a little grease on the back bearing and assembled in reverse order ( after using a piece of 24 gauge wire to hold the brushes back ).

I bought a proper plug at FLAPS for the sense and idiot light wiring, a Dorman 85841. I'll wire it in this afternoon and should be on the road this afternoon. The only question I have left to answer is what kind of a bulb should I use for the idiot light?
 
I temporarily wired in a #53 and it worked great. I'll make a run to Fry's (electronics place) in the morning and find an appropriate socket for the #53 or a better lamp/socket from their selection.
 
Bill Hanlon said:
The "B" jumped to the alternator output post is also a problem. B is the voltage sense back into the alternator. Right now it is sensing (and causing the system to regulate to) the output of the alternator. You need to disconnect it from the alternator output and connect it to somewhere deep inside the electrical system. Any hot point on the fuse box is best. That way the regulator will be "seeing" system voltage, not output voltage of the alternator.

Give it a try.
Click to expand...

Read back through the post & realized I misspoke. I have B to the ignition & D to the alternator post for constant hot. I'm still going to reroute the sense wire to a lead under the dash. I also stumbled across a post where the relay from a Volvo was used, looking into that option:
http://www.jeepforum.com/forum/f12/ford-taurus-wiring-solution-cheap-1325896/
 
Decided to stop by Pep Boys to check out their selections of e fans. Ended up buying a 17" two speed with the controller. Used my phone to take advance of the 25% discount for buying online and saved $50. Started the install and should finish up this evening. I got to thinking, this has a dual fan controller, I've got a smaller I believe 10" fan laying around. Would there be any benefit in installing both? The 17" mounted as a puller & the 10" mounted to the ac condenser as a pusher?
 
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I did some research & found that adding opposing fans would cause it to run hotter so I left well enough alone.

Finished up the fan & harness install and rewired the sense wire to a hot in the dash. Runs good holding @ about 12 volts with the fan on low, but drops significantly when the a/c kicks on or if I turn on the lights. This isn't new, just dragging my feet because I hardly ever drive at night. I'll be installing headlight relays soon so hopefully that helps out.

I uploaded a video here.
 
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mobileortho said:
I did some research & found that adding opposing fans would cause it to run hotter so I left well enough alone.

Finished up the fan & harness install and rewired the sense wire to a hot in the dash. Runs good holding @ about 12 volts with the fan on low, but drops significantly when the a/c kicks on or if I turn on the lights. This isn't new, just dragging my feet because I hardly ever drive at night. I'll be installing headlight relays soon so hopefully that helps out.

I uploaded a video here.
Click to expand...

Adding a relay doesn't change the total load on the system. It can, however, change exactly where the load is drawn from, and the wire size carrying that load. Biggest benefit of a relay is using a power sourced from a wire sized, and fused or with circuit breaker capable of carrying the amperage needed for your headlamps, or fan, or A/C compressor. Add up these major loads, and make sure you have an alternator with adequate ampacity. Bill Brubaker
 
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