Upgrading 4-Prong to 7-Prong - Isolator??

[clkelley564]

OK, since I'm ordering a new T@B next month I need to upgrade my flat 4-prong to a 7-prong and I do want to charge my camper battery with my tow vehicle. (2002 Explorer Sport Trac) I also want to be able to isolate the two just by taking the keys out of the ignition. (I may occasionally do some quick boondocking overnighters at Flying J or Wal-Mart and won't disconnect).

I called the U-Haul place and they said the upgrade would be no problem except for the isolator. Referred me to the dealer. Don't want to pay dealer prices. Is this something any auto electric place should be able to handle?? Or is the dealer my best option??

What do I need to specifically ask for when arranging this install. (Don't want to do it myself, but don't want to pay dealer prices either) Or, should I ask the RV place to add the isolator to the T@B??

(Oh and just an FYI, I already have the heavy duty Class III hitch with 2 inch receiver and I'm having a transmission cooler installed)

[Dale M.]

All you need is simple relay between battery on tow vehicle and 7 prong connector on rear of vehicle (12 volts pin)... When key is on, relay is operated making connection between tow vehicle battery and trailer battery, when key is off connection is "broken"...

If place you are having do the work does not understand "put relay in 12 volt supply lead", you dont want them to even touch your vehicle. Go find another shop...

Dale

[mrainey]

I had my Highlander converted at the local RV dealer yesterday - flat four-pin to seven round.

They charged $103, which may be way out of line , or not. I'm a total electrical dunce so had no other option.

I didn't think about an isolator. I see they charged me for a 20 amp circuit breaker - would that qualify as an isolator? If so, when would I want to use it?

[clkelley564]

The reason you would want an isolator is if your Tow Vehicle is charging your camper battery while on the road, if you stop overnight (or for more than an hour) and don't disconnect your camper from your vehicle, your vehicle battery could be drained.

It is just an extra safety feature. It prevents your vehicle battery from being drained, and it ensures you go down the road with your trailer lights working (in case you forget to hook things back up after stopping for dinner, or after stopping overnight at Wal-Mart, or after strolling through the flea market for a couple of hours).

Taking your keys out of the ignition is a natural no brainer thing to do. Disconnecting the electrical on the trailer and reconnecting it is not always a natural thing to do.

[clkelley564]

If place you are having do the work does not understand "put relay in 12 volt supply lead", you dont want them to even touch your vehicle. Go find another shop...

Dale

Thanks!! That's the kind of information I needed.

I'm going camping this weekend, but I think I'm going to dedicate next Saturday morning to getting my truck upgrades done. We actually still have a few places around here that are open till noon on Saturday :-)

[BrwBier]

I had my Highlander converted at the local RV dealer yesterday - flat four-pin to seven round.

They charged $103, which may be way out of line , or not. I'm a total electrical dunce so had no other option.

I didn't think about an isolator. I see they charged me for a 20 amp circuit breaker - would that qualify as an isolator? If so, when would I want to use it?

If your prices are like around here, then you got a good deal. You basicly paid $30 for the connector and a little less than a hour labor. Very fair I would say. The circuit breaker is not an isolator, it is mounted in the battery positive wire as close to the battery as practical. It protects the B+ wire from any problems as it runs to the rear of vehical.
Brwbier

[len19070]

Don't use an isolator, it's costly and isn't necessary. Go to any auto parts store and for about $10 get a 3 pole solenoid. Bolt it to your wheel well (that's its ground) One wire from the battery to the solenoid, a second out of the solenoid to the trailer and the third little one to an ignition hot wire. Ignition on, engaged...ignition off, isolated. Done.

Then your lights are hooked in. The 7 plug has the colors labeled on it. If you have a flat 4 line the conversion is;

Yellow= left turn, on the 7 plug that wire goes to red.
Green= right turn, on the 7 plug that goes to brown.
brown= running lights, on the 7 plug that goes to green
white goes to white. Not the center terminal, the one marked white.

The wire from the solenoid goes to black.

Somebody somewhere will post a drawing of this, infact theres a drawing that comes with the plug.

Don't just match colors! Match what they do.

Hope this helps. Its really not hard.

Happy Trails

Len

[mrainey]

Thanks BrwBier, good to know. My car's been parked for well over a day and the battery's fine, so I guess (hope) things are okay.

[Dale M.]

Don't use an isolator, it's costly and isn't necessary. Go to any auto parts store and for about $10 get a 3 pole solenoid.

Len

Just be sure solenoid (relay) is rated for CONTINUOUS operation , not INTERMITTENT like for starter applications...

Dale

[Podunkfla]

Don't use an isolator, it's costly and isn't necessary. Go to any auto parts store and for about $10 get a 3 pole solenoid.

Len

Just be sure solenoid (relay) is rated for CONTINUOUS operation , not INTERMITTENT like for starter applications...

Dale

Like Dale said... make sure relay is rated for CONTINUOUS operation, Not like most common starter relays (they will get hot and burn out). Relays are not expensive, here is one source:
http://www.electricscooterparts.com/relays.html

This little 12v -30amp will do most lighting applications and they are less than 3 bucks. Of course, you can get larger capacity relays too.


How to wire 'em...

[Dale M.]

Like Dale said... make sure relay is rated for CONTINUOUS operation, Not like most common starter relays (they will get hot and burn out). Relays are not expensive, here is one source:
http://www.electricscooterparts.com/relays.html

This little 12v -30amp will do most lighting applications and they are less than 3 bucks. Of course, you can get larger capacity relays too.


How to wire 'em...

Yah...BOSCH relays rock...

Dale

[asianflava]

We did all kinds of things with those relays when I used to install stereo. On some cars, the polarity of the door locks would switch to open or close them. We would have to configure those relays to switch like that even though the alarm only had a + pulse. The more features a customer wanted the alarm to do, the more relays we'd have to use.

Nowadays, the alarm companies are hip to it and build the relays into the main module. It makes installation much easier=faster=more money for the shop.

[bdosborn]

Here's a tip; if a relay says it is "normally open" it means its open in the de-energized state. Same for "normaly closed", its always the de-energized condition. Its kinda backwards from what I thought it should be.
Bruce

[clkelley564]

Just an update. Well I finally did what I should have done in the first place, go to "Dad's Electrical Shop" (his toolkit and my driveway). He knew exactly what I was talking about and offered to teach me how to do it myself. I also found a step-by-step instructions and parts list on the tabtrailers group on Yahoo. Don't know how I missed it before I posted this. So I'm all ready to go!! For the person who got their charging wire and 7-pin installed for just over $100, you got a great deal, as just the parts I bought were $70.00 with tax. Granted, the dealer purchases all these items in bulk and probably pays 1/4 of the individual prices, especially the wire, 35 ft was way more than I needed, but my choices were 6 foot or 35 ft.

Parts necessary from
http://www.radioshack.com/
1 ea. # 275-226 12VDC/30A SPST Automotive Relay, $6.49
1 roll #278-569 35-ft 10-Gauge Hookup WireBlack, $14.99
1 pkg #270-1084 25A Blade-Type Automotive Fuses, $1.99
1 ea. #270-1234 30-Amp Inline Blade-Type Fuse Holder, $2.49
1 pkg #278-1632 4" Nylon Wire Ties, $1.99
1 pkg #64-3111 12-10 Gauge Shrink Butt Connectors, $1.99
1 pkg #64-3140 Low-voltage Tap-Ins, $1.99
1 pkg #64-3120 Insulated Ring Connectors, $1.99
2 pkg #64-3137 1/4" Crimp-On Quick Disconnects, $1.99
Combo 7-pin Round/4-pin flat adapter with mounting bracket - Auto Zone $24.99