Actually, i tried it when i went out to my car. My RPMS's DO drop a tiny bit when i turn the rear defrost on, and then jump up a bit when i turn it off. About 50 or so RPM. But my car does it too. Never noticed it


I can see why though. Defrosters work on resistance which is high current draw through the conductive "wires" across the glass. The high resistance causes them to heat up. I wouldn't be surprised if there was 10-15A of current going through the defrost.

 

I don't think there is constant power to the rear defrost. If that were the case, it would always be on. The power doesn't go on to the defrost until you push the switch to do so.

 

you're wrong. My taillights which are also blinkers had to run off continuous power (for hazards)... since I dont have Bose unit, there was nothing else back there - and I didn't want to wire from battery all the way back there... I'm wired into the defroster for continuous power.

as to the amount of current... that's different - but turning it on isn't going to change enough to drop his rpm. Which is what my post stated.

 

I think there is a semantic difference here. You are referring to the continuous availability of power -- an always-energized circuit. That's not the same as "always-on" meaning current is always flowing.

Always energized = power is always available.

Continuous power = current always flows.

 

can someone please list all grounds(if possible) id like to know as well ,as i also are having some trouble with shifts,and current draw

 

Without looking at the schematics, he could be right.

It all depends on if nissan switches the grounding leg of the defrost grid and not the hot side. If that was the case he could tap into the hot side and flow current to whatever he needed power to. The grid wouldn't engage until the circuit is complete and the downstream leg is grounded.

I'd like to see the wiring diagrams to be 100% sure though.

Technically, if you assume a 20A draw through the defrost, you would calculate that as being an decrease of power by 0.32HP through the alternator. (20A v 12V = 240 watts x 0.00134 = .3216 HP) Shouldn't be enough to cause the RPM's to drop.

However, 20 mins ago i tried and my RPM's do in fact drop and increase as i turn on and off the rear defrost

 

Correct. And for the purpose of turning on the defroster = making the rpm drop, the right semantic in this case is that it does not have continous power in the sense OCG35 is talking about. aka constant amp draw.

 

OCG35 meant "continuously energized" -- power is available but not necessarily switched on.

Jeff92se meant "always on" -- current always flows.

Neither person was wrong, they just meant different things by the phrase "continuously powered."

Since power is the product of voltage and current, it is more clear to reserve that word for the times when both V and I are present as Jeff says.

 

I guess "continued available power" is how I should have phrased it... the defroster is powered from wire from battery - with a relay... obviously turn defroster on and relay allows current (I'm wired in off that power)...

what I was saying is, it's doubtful that simply activating that relay (turning defroster on) will cause rpm to drop... it doesn't happen in my car and I figured it was unlikely the reason for OP problem...

this is what I was saying - and I'm surprised yours dropped...

Here are some of the schematics:

 

I turned on the rear defrost today and my rpms in gear at a stop dropped by 100rpms.

 

Well, I'm really curious to see if the additional grounding wires will affect any of this, especially the trans stuff. Unfortunately, it won't be today...my wife drove it to work this morning, so maybe tomorrow.

 

I don't know if its my grounding kit or not, but I confirmed today - on, off multiple times, no deviation at all with rpm...

I'm really surprised its happening on other Gs... I can understand a 1975 Z or something... but its odd that it is happening to ppl in this car.

 

A forum member on another G/Z forum (which will remain nameless) made a damn good set of ground wires. I bought them and installed them weeks after buying the car. I noted a few minor improvements. Smoother shifts, better sounding radio. It might help to have a good ground wire set installed.

 

You're probably talking about sentientbydesign. I read great things about his kit but if I buy a set I'll buy them from Sean (SxExCx) to support our members.

 

I just inspected all of the ground wires under the hood that I could find. Nothing loose or disconnected, but the amount of rust and corrosion on only two of them was surprising. All of the other bolts under the hood are rust and corrosion free. It's like some kind of voltage issue with just those two grounds is causing rust/corrosion maybe? Not an area of knowledge for me...

Here are some pics:

Ground wire for the headlights


This one is right under the coolant overflow tank and runs up to the top of the engine on the pass side