Help!! Hooking up trailer battery charging wire on 99 Blazer

[halfdome, Danny]

I have a 99 Chevy Blazer with factory installed towing package. After going through my 7 wire harness and hooking up back-up lights for the tear I noticed the center hot wire for charging the tears battery wasn't hot. All but that wire and the blue brake wire were hooked up and fused through the engine compartment fuse block. The dealer told me where to find the ( trailer battery) wire and hook it to one of the terminals on the fuse box. The manual says to hook it to the starter solenoid. Which is correct and does this fuse box already have a wire to the starter solenoid? It says there is a 30 amp fuse to protect this circuit and I think it's labeled INT BAT I/P Fuse Block Feed but I'm really not sure . As you can see the red wire with factory connector is quite short and I don't think I would reach the starter solenoid. With this kind of set up do I need a battery isolater? I don't even know where I could install one. BTW last year I installed the best heavy duty altinator Kragin auto parts had. The chances of someone having the same vehicle are slim but I would think most GM products of the same age would be similar.
PS This vehicle was made for import to Canada & I found a oil heater 110volt wire & plug while under the hood, so I guess we could travel to Alaska or the East Coast. Danny

[madjack]

...Danny, if you have the manual, does it have a wiring diagram..if so, see where it shows to run the wire...if it shows going to the solenoid, then it MAY have isolation...

I would follow the manufacturers (manual) advice, before the dealer

You can do like the dealer sez and wire to the fuse block or directly to the battery with an inline fuse...you have NO battery isolation that way

madjack

[Nitetimes]

The thing to look for, is there one or 2 studs sticking up beside that fuse box? They may or may not have anything on them, odds are good they don't even have nuts on them. If they are there one of them should be hot all the time, the other should be hot only when the key is on and be fused with one of those large 30 amp fuses, that's the one you want to use for the charge wire.

Edit - just realized you have a heavy guage wire to what looks like a bolt. Is there another one of those bolts or a stud beside that? That would be the location to check.

[halfdome, Danny]

Madjack, All I have is the little owners manual that usually comes with a new vehicle, no wiring diagram at all.

Rich, In the left top corner is a bolt with what appears to be a red battery connection but I couldn't get my test light to come on with the engine on or off. On the top right corner there is a bolt without a nut like you mentioned and it too won't light up. I guess I'll need to run a longer test lead to another ground as what is available in the area seems to not work. Danny

[GeorgeTelford]

Hi

If you want to drag your leisure battery down to 65-70% charged (yes I do mean drag down)

Then find a wire thats hot only when engine running (thats different to just ignition on, if you find an ignition on wire then you could flatten your starter battery)

The best alround solution is to use a relay and power it via the alternator charge light (this will then only power the relay when the engine is actually running) theis then passes power back to the leisure battery (if the battery is below 65% then some charging will occur, If however you have fully charged the battery via a mains charger then it will be discharged down to 65% (ish) as you drive along.

[Jiminsav]

Danny, I was reading up on them 7 way plugs and they stated thet the center pin is generally used for back-up lights, not a hot wire. the 12 volt hot wire is on the outside pin somewhere..fur instance.
# Color Gage Circuit Function connector interior
1 white 10 common ground [7 way connector]
2 blue 12 electric brake
3 green 14 tail/running lights
4 black 10 battery charge (+)
5 red 14 left turn/stop
6 brown 14 right turn/stop
7 yellow 14 auxiliary/back up
NOTE: #7 is the center terminal and currently is most commonly used for backup lights.


Wiring Code 7 way Trailer End # Color Gage Circuit Function connector interior
1 white 10 common ground [7 way connector]
2 blue 12 electric brake
3 green 14 tail/running lights
4 black 10 battery charge (+)
5 red 14 left turn/stop
6 brown 14 right turn/stop
7 yellow 14 auxiliary/back up
NOTE: #7 is the center terminal and currently is most commonly used for backup lights.

[Nitetimes]

Rich, In the left top corner is a bolt with what appears to be a red battery connection but I couldn't get my test light to come on with the engine on or off. On the top right corner there is a bolt without a nut like you mentioned and it too won't light up. Danny

Sorry just got home. Check to see if all of the large fuses are installed, more often than not the charging circuit won't have a fuse in it.

[RKH]

Danny, I responded on Blazerowners.com but from your picture, the Stud 2 I was talking about appears to be the brass colored one in the upper right corner of the picture you've posted.

[halfdome, Danny]

Danny, I responded on Blazerowners.com but from your picture, the Stud 2 I was talking about appears to be the brass colored one in the upper right corner of the picture you've posted.

Hi, RKH So what I'm getting from your reply is that I should attach my red wire to the same post (left hand one in photo) and install a battery isolator between that post and the tears battery connection. George was saying something about draining my fully charged battery and that could be simply fixed with a cut off switch and I could switch it back on when the battery is low. Some of Georges post went way over my head and that may be my fault or it could be the different way we all talk on different sides of the pond, I don't know, thanks anyway George. Jim my schematic shows a hot black wire on the side and a battery hot red wire in the middle. I followed the schematic I have in hand. As far as I'm concerned it doesn't really matter where the wires are placed as long as they match tow vehicle to trailer. If someone was to steal it the incompatible wiring may alert law enforcement. Danny

[Nitetimes]

If someone was to steal it the incompatible wiring may alert law enforcement. Danny

Don't know about that but the smoke trail certainly might.

[GeorgeTelford]

Hi Danny

Many people mistakenly believe that an alternator is a good battery charger, this is not true, at best it can only charge to around 65%, this maybe OK if all you use is a light.. I have seen that you have a Fan, Tv and lights, lets look at some numbers

Lets say you have A 100 ah battery, if its charged by the wire you have 65 Ah, less the 50% that you should not use leaves 15 Ah ( you can use more but you are killing the battery off )

If charged via a decent mains charger ( and not connected to alternator on the way ) you would have 50 Ah thats 3.33 times more power to play with.

I originally discovered this by accident, In my old campervan I used to hook up at home and charge the batteries and while out camping for weekends never ran out of power (even for long weekends fri to mon night)

Eventually I decided to add a charge wire, first weekend out ran out of power on the second day, the same the next weeekend (I was still fully charging the batteries on hook up at home first) anyway this bothered me so I removed the charge wire, next weekend no problem, to cut a long story short having checked it out thoroughly the above is true

[halfdome, Danny]

Hi Danny

Many people mistakenly believe that an alternator is a good battery charger, this is not true, at best it can only charge to around 65%, this maybe OK if all you use is a light.. I have seen that you have a Fan, Tv and lights, lets look at some numbers

Lets say you have A 100 ah battery, if its charged by the wire you have 65 Ah, less the 50% that you should not use leaves 15 Ah ( you can use more but you are killing the battery off )

If charged via a decent mains charger ( and not connected to alternator on the way ) you would have 50 Ah thats 3.33 times more power to play with.
I originally discovered this by accident, In my old campervan I used to hook up at home and charge the batteries and while out camping for weekends never ran out of power (even for long weekends fri to mon night)

Eventually I decided to add a charge wire, first weekend out ran out of power on the second day, the same the next weeekend (I was still fully charging the batteries on hook up at home first) anyway this bothered me so I removed the charge wire, next weekend no problem, to cut a long story short having checked it out thoroughly the above is true

George, I have taken stock of what you have posted here and in other threads on this subject and I appreciate your expertise in this field. The fact remains is that all of our camping is primitive and eventually I will need to rely on the tow vehicles charging system no matter how inadequate it may be. We are planning on a week or more for some of our trips and the original charge from my battery tender won't last forever. For this reason it is necessary that I figure out the proper way to do the hook ups in the tow vehicle and I will put a battery cut off switch on the hot vehicle wire to the trailers battery. It will most likely be in the same box as my trailer battery is for my convenience. I know I won't get the maximum usage out of my battery if it runs down past a certan point and even though I don't enjoy throwing away money a fifty dollar battery that would last even one year is cheaper than one night's stay at a cheap Motel 6. Danny

[GeorgeTelford]

Hi Danny

I hear you on the cost and usability issue, but you could try this, why not charge fully via battery tender (is that a staged charger?) then do not use the alternator wire until after you have run the battery down, that way at least you get to use the charge you have put in and then use the minimal charging when you have to (best of both worlds then)


BTW beware of putting a switch in the battery box, while charging gas is created, switches create sparks when being disconnected, you could end up with an exploding battery, this is the same reason that fuses should not be in the battery box either.

[Elumia]

Why not get a small solar panel that is not permantly attached to the tear so you can move it into the sun and keep your battery topped off that way? Just another though - less wiring hassle too.

Mark

[halfdome, Danny]

Hi Danny

I hear you on the cost and usability issue, but you could try this, why not charge fully via battery tender (is that a staged charger?) then do not use the alternator wire until after you have run the battery down, that way at least you get to use the charge you have put in and then use the minimal charging when you have to (best of both worlds then)


BTW beware of putting a switch in the battery box, while charging gas is created, switches create sparks when being disconnected, you could end up with an exploding battery, this is the same reason that fuses should not be in the battery box either.

Hi George, That is exactly my plan and this is my battery tender. We have had the battery connected to the battery tender now for two weeks and have watched a movie for at least 1/2 hour every night like we were on house hold current. Thanks for the heads up on the switch I'll locate it elsewhere. Danny