Looking for a wiring diagram for my 1996 GMC C3500 DRW 6.5 with dual alternators.

[Rachet]

Hi guys, as some of you may know my truck is a former ambulance. I have removed the two ambulance batteries which were connected to the two engine batteries. The truck is also equipped with dual alternators. Can anybody direct me to the right place to find the wiring diagram?

 

[Will L.]

Your best bet is get ahold of the body manufacturer. Each company can wire it up however they choose like a guy in his back yard.
I used to be half owner of truck equipment company and built a few myself.

 

[dbrannon79]

I'm betting that the second alternator was isolated to the rear batteries so that they would never feed off from the engine batteries. you might look at tracing the main power wire off the second alt and see if it didn't run direct to the rear batts. if you are wanting to still run dual alt's on the engine batteries, you could run the main power wire to the passenger battery with a heavy fuse link and just tie in the connector wire to a switched pos (+) from the key. just watch the output amperage on each alt so that their not fighting each other which sometimes happens.

to prevent them from fighting each other you would need two externaly regulated alternators and one single heavy duty regulator to draw from both alternators. it's not hard to wire up the existing alternators to use an external regulator. you would just need to tap into the three phase ac current leads inside both alternators (6 wires total) and go into the external regulator of choice. can even wire it to use one of the alternators internal regulators for total output. but keep the engine alt connector hooked up for the tach in the dash.

 

[MrMarty51]

There also is the option of battery isolators that once the equipment batteries is fully charged the isolator puts everything to the vehicle batteries.
With the isolator, when the ignition switch is off, it does not allow the behicle batteries to be drawn frum.

 

[Rachet]

Thank you! If the second alternator is charging the ambulance batteries I can use that to charge my new lithium battery system via dc to dc charger for the ambulance section. Right now I am in need of a diagram showing the stock battery cable routing so that I can eliminate the connection to the rear batteries.

 

[MrMarty51]

@Jaryd
Do You still have Your books You was trying to sell ?
Maybe they will fit this application.
Jaryd has not been on in a while. I hope He is okay. If His email has not changed He should get a message and maybe pop on in.

 

[Will L.]

Buying an ambulance, really you are going to have to physically chase the wires down.

IF your are lucky enough to get a schematic for the a ambulance itself, a schematic still doesn’t tell you where everything is at. It will just show the circuits.

its like in your house, breaker #5 can control the receptacles in 2 bedrooms, but won’t say if the wire goes in from the attic, from under the floor, and what order ot goes from one recep to another.

 

[dbrannon79]

follow the cables from the rear up to the front end, if they are connected into the truck side, they are most likely going to the aux fuses in the under the hood fuse panel. on the normal truck application there will be a power wire from the back of the alt to the drivers battery pos post and then branches off from the battery to the under hood fuse box for distribution. for the aux fuses, those are usually big "maxi" style fuses at the rear side of the box and have two 10mm studs sticking out from the back of the box. mine didn't have any cables attached to the studs, yours might have a cable or two attached going to the rear for charging the rear batts. if this is true, your second alternator will be working together with the other to charge the entire system. isolating them will just be dossconnecting the power wires from the aux studs in the panel and running them to the second alternator, disconnecting the existing cables from the rear of the second alt.