Alternator Bypass Wire Routing

[Mrbill426]

Great information 

[chargerdon]

  This bypass thread is great. I've read about it on several boards. I do have one question about it. Why couldn't a person just put a jumper wire between the two posts on the ammeter instead of disconnecting it entirely? Takes the load off the ammeter. The bypass wire shown installe in this thread takes the load off the harness connection and ammeter anyway. Just wondering.
Terry

Terry, there is no need to do all of the work to take out the dash and then put a jumper wire across the Ammeter.  Look, the Ammeter IS NOT a source of a problem...   The problem is the insufficient 12 gauge wire that runs thru the bulkhead, thru the ammeter, then to junction which is 5 different wires welded together, then back thru the bulkhead connector carrying all of the car's current.   With the bypass wire in place that doesn't happen !!  Without the bypass wire, the problem is more likely to be at the bulkhead connectors melting, and catching on fire, not the ammeter itself !!

If you ever take an ammeter apart what you would find is a Solid Copper Bar...between the two contacts.   When current runs thru that copper bar it creates a magnetic flow...needle which is NOT electrically attached follows that magnetic pulse to the left while discharging, or to the right when charging...ie the current flow.   With the bypass wire at LEAST 10 ga, or 8 or better gauge in place the current runs instead to the starter relay, to the battery and the bulk of it doesn't go thru the bulkhead connector.         The ammeter itself creates no problem, but, with the bypass in place it wont be accurate !!    Recognize that fact and you can leave it as is forever !!   However replace it with a voltmeter with just one wire, and then a ground wire and you again have a functioning gauge that makes sense.  Without the voltmeter in its place, if the alternator dies or the voltage regulator malfunctions, you wont know it until the battery goes dead!!   Maybe while your driving it. 

[Mrbill426]

Am I missing a point here?  Maybe I need need to see a schematic but is this whole bypass a run of one gauge cable?  I read 6 or 8 gauge on one end but then 10 or 12 gauge on the other with a fuse link... isn't that a step-down that would cause resistance and heat? 
Am am apparently not getting it 

I have read many of the threads on multiple forums for this topic and while there are some diagrams, I haven't seen anyone post actual pictures of the alternator bypass, so I thought I would start a thread to help future clueless people like me. Ordered a 6ga cable from @crackedback  (Thanks Rob), so I know I need to go from the alternator stud to the starter relay. What is the route people generally take to get there? Just following the original route of the smaller gauge cable until you get to the firewall and continue on to the starter relay?

After that, I know I can leave the original wiring in place so it is running in parallel. I will then work on seeing if I can get under the dash, disconnect both sides of the ammeter, and wire them together on one side of the ammeter. Is this still the recommended action to perform the bypass? If reaching back up to the gauge becomes a pain, is just taking both ends, connecting them with a separate nut and bolt, then wrapping the whole connection in tape acceptable since it is an inline connection?




Updated to show steps and options:

   
• Disconnect the negative terminal of your battery to remove power and avoid unnecessary risk
• Choose and mock up your route - The 2 most popular routes are:
  
  
        
  • Roughly the original route - Following the original alternator cable across the intake manifold and around the back of the engine, but continuing around the driver's side fender to the starter relay instead of through the firewall (see Alternator Bypass Back Route.jpg)
  • Run Towards the Front, the idea being the cable is further away from heat - From the alternator over to the passenger side fender forward to the front of the radiator support, through an existing hole on the driver's side, under the battery tray and back up to the starter relay (see Alternator Bypass Front Route.png)
• Lay the cable in the proposed route to ensure you have enough length. The thicker 6ga or 8ga end connects to the rear terminal post of the alternator. The smaller 10ga or 12ga end (orange in my case) with a built in fusible link connects to the positive terminal of the starter relay or battery itself.
• Carefully lift off the protective boot on the back of the alternator terminal, then loosen and remove the nut with a 7/16" wrench. Add the new cable and tighten the nut back onto the alternator (see Alternator end attached.jpg). Slide the protective boot back down over the nut.
• Run the cable properly through any supports/loom in your desired route. Do not fasten or ziptie in place until starter relay connection complete.
• Loosen and remove the nut on the positive terminal of the starter relay using a 1/2" wrench. Add the new cable and tighten the nut back onto the starter relay terminal (see Starter Relay end attached.jpg).
• Fasten the rest of the wire using zipties to supports or loom.
• Reconnect the negative terminal of the battery and test
• Finish your beer

At this point, you have now removed the bulk of the power load from the stock wiring harness through the firewall. It is a good idea to also disconnect the ammeter leads, connect them together with a nut and bolt, then wrap them in tape to protect them from contacting the grounded firewall.

[dodj]

  Look, the Ammeter IS NOT a source of a problem... 

Actually, the ammeter is half of the reason for doing the bypass. The bulkhead connector is the other half. 

[mopar jack]

Since I have a stock type alternator I used the wire size  that Erhenburge recommended. 10 gauge for the bypass and 14 for the fusible link. The link wire can be found at most auto parts stores.

[chargerdon]

Here is a picture of a disassembled alternator from a 1967 Dodge Charger.   I have seen the insides of our 70-74 challenger ammeter and it is nearly identical.    Notice that the inside is a solid copper bar between the contacts.   THIS would never cause a problem so long as the connections are tight.   

The problem is in trying to carry all of the cars power thru the 12 gauge wire, thru the bulkhead connectors which are very week, then to the ammeter and then back thru the bulkhead connectors.   (note: 12 gauge wire is only good for up to 20 amps safely, and 10 gauge up to 30 amps, 8 gauge 55 amps ) With the alternator bypass wire in place you cut down the amount of current running thru those wires to only what is needed to run the car. not to recharge the battery  The ignition system (coil, ECU)  uses about 6 amp..   So, this simple wire from the alternator to the starter relay corrects half of the problem.   The other half is still the original wiring which is 12 amp thru the bulkhead to amp gauge to the main wiring splice and then back thru the bulkhead connector with 12 gauge and when you turn on the headlights they and the associated parking lights draw about another 15 amp so now you have a total of around 20-22 amp...   Turn on the radio and heater blower, and now your well over the 20 amp of the 12 gauge wires.  This is why the headlight bypass is the second half of the recommended bypasses.  I rarely drive my car at night, so i haven't bothered with the second part.   I probably will however, as i have seen signs now that the headlight switch has overheated some. 

To read more, including the second half of the ammeter bypass to to: http://www.madelectrical.com/electricaltech/amp-gauges.shtml
  and part two http://www.madelectrical.com/electricaltech/amp-gauges2.shtml     In these articles they say the the ammeter is a problem, but, AND THIS IS MY OPINION BASED ON SEEING THE INSIDE OF AN AMP GAUGE...   It is not the gauge itself, but rather the undersized wiring and bad bulkhead connectors that are used to make the ammeter functional that is the problem.   

[Scooter]

Check this cool photo of my 67 Fairlaine taking the ride of shame after I stopped for gas and could not get it to start for the second time in a few months...



Cause... bad ammeter.... no power.

IMHO... bypass and get a volt meter.

[70rag383]

Nice Fairlane! Is that a 390?

I did the same drive of shame a few months ago for the same reason and was in no mood to take any pictures.  I immediately cleaned up the bulkhead connectors, did the ammeter bypass and installed a headlight relay kit.

[Scooter]

Nice Fairlane! Is that a 390?

I did the same drive of shame a few months ago for the same reason and was in no mood to take any pictures.  I immediately cleaned up the bulkhead connectors, did the ammeter bypass and installed a headlight relay kit.

Yup. 390FE. I found the ammeter connection hidden under the battery tray. Owned the car over 25 years and did not know it was there.

[mopar jack]

chargerdon thanks for the pic. I have had connectors at amp meter come loose and loose connections can get hot so  I like to solder the connection isnside the meter for added protection. I marked your photo thanks.

[dodj]

Plenty of Chrysler ammeters have melted and/or caused fires.  Even if you have done the bypass, you don't know how damaged the ammeter is from the previous 40 years.  It is still a potential source of grief. Disconnect it imo.

[crackedback]

Having seen ammeters short into clusters... YES, they can be a problem.

It's a useless gauge with a wire around in place.  The base internal workings of the ammeter aren't generally the issue.

Pick how you want to do it and go. 

[Jim AAR]

Do you need the In Line Fuse? Or can you just run an 8 gauge wire end to end instead of stepping it down with an Inline fuse?

My Ammeter still works on my Standard dash, but I think after reading all these posts i'll run the bypass and disconnect the Ammeter.

I only drive mine a few times a week so starting it up and checking the voltage with a voltmeter when i go out and when i come back to make sure its still charging isn't that big a deal, it would be if i went on a longer trip, then i'll have to install a voltmeter I guess to be on the safe side.

[chargerdon]

Can anyone recommend a headlight relay bypass kit ?   

[dodj]

Can anyone recommend a headlight relay bypass kit ?

I made my own, but crackedback has received numerous kudos for his/her kits.