Hot start wiring option question for GPS gauge set and master battery shutoff

[jwsnake56]

I installed a master shutoff switch in the main power feed from the battery. Is it a good idea to bypass the master shutoff with a wire that feeds power to just the GPS speedometer and the clock of the electric gauge set? Is there too much current draw that it would drain the battery over the 3-4 month downtime of a typical Midwestern winter?
John S.

[edwardb]

Speedhut says the GPS hot start function only draws 25 micro-amp draw. So no worries there. I haven't seen them list power draw for the clock. If similar to other quartz movement clocks, which I suspect it is, probably no worries there either. Most will run a year or so with a single AA battery. So I doubt either will run your battery down over that 3-4 month period.

Bigger question though is what to do with the battery during the winter. If your storage location is really cold, may want to consider disconnecting/removing and storing in a warmer spot. Also might want to think about a tender or at least giving it a charge every month or so. That's what I do with mine during the winter using a CTEK 3300. One or both of these approaches are probably better for the battery in the long run (at least IMO) and make the current draw of the GPS and clock a moot point.

[jwsnake56]

Well if future winters here in Ohio are like this one, it won't end up in storage much at all ��. My garage isn't heated but it stays about 40-45'F through the winter. As far as running the hot start wire from the battery side of the switch, is that a wise option. I was also a little confused about the best place to put my mega fuse. I am planning to bring a heavy 6ga wire on the switched side over to the starter, and an 8ga wire up to the mega fuse then on to a distribution buss block. All the power connector wires from the RF harness will be connected to the buss block including the cable to the alternator. Is this the way to wire the fuse?
Thanks for the helpful advice. I refer to your #7750 build thread for a lot of guidance as my build is very similar.
John S.

[edwardb]

Well if future winters here in Ohio are like this one, it won't end up in storage much at all ��. My garage isn't heated but it stays about 40-45'F through the winter. As far as running the hot start wire from the battery side of the switch, is that a wise option. I was also a little confused about the best place to put my mega fuse. I am planning to bring a heavy 6ga wire on the switched side over to the starter, and an 8ga wire up to the mega fuse then on to a distribution buss block. All the power connector wires from the RF harness will be connected to the buss block including the cable to the alternator. Is this the way to wire the fuse?
Thanks for the helpful advice. I refer to your #7750 build thread for a lot of guidance as my build is very similar.
John S.

Our winter here in SE Michigan has been relatively mild here as well. (As I'm typing this it's snowing outside. But still...) My garage also stays about 40-45 with no heat. But I still throw the CTEK on my battery every month or so. Gives it a peak charge and the green light tells me it's still healthy. Before when I had to store off-site in a completely unheated and much colder location, I removed the battery and kept in my basement. Maybe not necessary, but I felt better doing that.

No issues with taking the hot start "always on" feeds from the battery side of the switch. It's done all the time with engine ECM's, for example, where it's recommended to always have them powered. The clock and GPS function you're planning are very low current draw, as discussed, but still good practice to have a fuse in the lines. Other than that, you should be good to go.

For the mega fuse you asked about, while one is not shown in the Ron Francis harness, I think it's good practice to have a fuse between the alternator and the harness. So I add one. But only on the alternator line. There's no reason IMO to have it between your switch and the RF harness power. All the circuits in the RF harness go through the fuse panel and are individually fused. On #7750, plus my latest build, I used a Blue Sea Systems 150A bus bar for the RF harness power connections and tied that to the switched side of the master disconnect. Then fed the alternator through a mega fuse off the bus bar. Hope that makes sense.

[jwsnake56]

On #7750, plus my latest build, I used a Blue Sea Systems 150A bus bar for the RF harness power connections and tied that to the switched side of the master disconnect. Then fed the alternator through a mega fuse off the bus bar. Hope that makes sense.
I've looked at the pictures that you have in the build thread and wasn't sure if the red wire coming to the buss bar was the feed from the switch or line out to the alternator. Thanks for clarifying that. I hadn't considered that the harness fuse panel isolated each of the other circuits.
One last question (for now), whose headlight relay system did you use? My night vison is not what it was in my 20's and I like nice bright (meaning high powered) headlighting. I'm not sure the stock wiring with all the current through the switch is a good idea. Relays seem a better option.
Thanks again,
John S.

[edwardb]

I've looked at the pictures that you have in the build thread and wasn't sure if the red wire coming to the buss bar was the feed from the switch or line out to the alternator. Thanks for clarifying that. I hadn't considered that the harness fuse panel isolated each of the other circuits.
One last question (for now), whose headlight relay system did you use? My night vison is not what it was in my 20's and I like nice bright (meaning high powered) headlighting. I'm not sure the stock wiring with all the current through the switch is a good idea. Relays seem a better option.
Thanks again,
John S.

For my two Mk4 builds, I used a solid state headlight control module from American Autowire. So no relays. They work very well for me. But unfortunately American Autowire took them off the market, so no longer an option. There are other solid state options, but I'm not personally familiar with them so cannot comment. I used the standard VW style latching relay setup on my Mk3. It was OK, and I would say most are still using something similar.

For really bright headlights without having to do anything to the wiring, I'd recommend looking at LED's. There are lots of options. I chose these for my latest build: http://www.watsons-streetworks.com/exterior-lighting/headlights/led-headlights-251xx-jeep-7-inch-round-bulb-bulbs. They fit the plastic headlight bucket that comes with the kit. There is an amplifier that needs to be mounted, but easy and they plug right into the existing harness. They only draw 1.8 amps each (I measured them) which is a fraction of the stock lights, so easily handled by the standard wiring and switch. They are very bright. No comparison to the stock halogens.

[GFX2043mtu]

If you are running a battery cut off it's always best practice to have all devices that use power downstream of the cut off, and all devices that make or store power (battery and alternator) wired upstream of the cut off. The reason is for this is because the point of a power cutoff is to completely cut power to the drive train and electrical system in the event of an emergency. Any bypass of power around the switch can mean that in the event it's needed enough power can be pulled through other wires to power the ignition or any shorted circuit . This can keep the engine running and other electrical systems live, this in turn can lead to fires etc. even if the wire the device is powering may consume very little power. I know yours is probably a street car but what's the point of wiring it at all if it won't ever work as intended. Just leave a battery tender on it and the battery key in.

[edwardb]

If you are running a battery cut off it's always best practice to have all devices that use power downstream of the cut off, and all devices that make or store power (battery and alternator) wired upstream of the cut off. The reason is for this is because the point of a power cutoff is to completely cut power to the drive train and electrical system in the event of an emergency. Any bypass of power around the switch can mean that in the event it's needed enough power can be pulled through other wires to power the ignition or any shorted circuit . This can keep the engine running and other electrical systems live, this in turn can lead to fires etc. even if the wire the device is powering may consume very little power. I know yours is probably a street car but what's the point of wiring it at all if it won't ever work as intended. Just leave a battery tender on it and the battery key in.

In general I agree with your points and the function of the cut off. But the OP is asking about two functions: (1) A GPS "keep alive" function that keeps enough power to the GPS speedo so that it remembers its current position to enable fast signal acquisition at start up. Couple seconds versus potentially much longer if the power has been off for a while. (2) Power to the dash clock so that it doesn't need to be reset each time the master switch is turned off. Everything else is on the switched side of the disconnect. Properly fused, as I mentioned, these two connections are perfectly safe and have zero possibility to keep the engine running or the rest of the electrical systems alive with the master switch off. This isn't really anything special. DD's are typically wired the same way with certain functions, e.g. the ECM or PCM, always powered. The Ford crate motor Coyote I just installed uses an OE style power power distribution box (PDB) which contains several hot at all times (HAAT) circuits.

[jwsnake56]

For really bright headlights without having to do anything to the wiring, I'd recommend looking at LED's. There are lots of options. I chose these for my latest build: http://www.watsons-streetworks.com/exterior-lighting/headlights/led-headlights-251xx-jeep-7-inch-round-bulb-bulbs. They fit the plastic headlight bucket that comes with the kit. There is an amplifier that needs to be mounted, but easy and they plug right into the existing harness. They only draw 1.8 amps each (I measured them) which is a fraction of the stock lights, so easily handled by the standard wiring and switch. They are very bright. No comparison to the stock halogens.
I love those headlights. The video on the website is very convincing. But just one problem; I also saw the headlight chime kit, and the illuminated cupholders, and the trunk tilt switch, and the list of wiring mods just keeps growing! :)
Thanks for the helpful tips,
John S.