Re:Re:Re:2015 Armada No Heat

Yes, another no heat complaint. Another tech says he had a hot line to the heat core and cold out so he back flushed it. I have hot line into the water valve near the fire wall before the heater core and maybe, maybe, a warm hose coming out.

I forgot that this is not just a solonoid that is opened or closed and thought I had no power at it from the AC auto amp, so I replaced that and when I didn't fix it I realized it's supposed to open and close from the AC auto amp based on temp knobs and only moves when the knobs are actually turned. It's got gears, not a solenoid. Both wires are grounded until the knob is turned then one side becomes a power depending on if it's opening or closing. Idiot, I knew this too. I took one apart like a year ago.

Knowing that, I have 10.5v on it when the temp knobs are turned. SI says it should be B+. I also have 10.5v coming out of the AC auto amp, so it's not high resistance between the two. Tested powers and grounds to the amp and all are good with near B+ in and 40mv on ground. My power probe makes the valve move with 12v.

Now, are the gears a little rough or something and my 12v blast is enough to move them but the "normal" 10.5v it's getting isn't, and maybe it would be enough for a new valve, or is my AC auto amp bad?

If you read my recent Pathfinder no heat post, you might understand why I'm questioning the new amp I put in it. My parts dept was also having a hard time determining the part number for some reason and had to contact Nissan about it, so I'm not exactly filled with confidence there.

I always struggle when numbers are like this because voltage drop is such a big concern. It seems ridiculous that it would be designed that way. It makes me want to just use a test light and focus less on the specific numbers, but I've definitely had cases where that would have burned me, so I don't know.



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I've never played with one of these water valves before, so bear with me. :silly: If I understand you right, this valve is actually motorized. I don't know that it'll change your diagnosis, necessarily, but it might be fun to take a current reading with an amp probe during valve opening. If anything, it might streamline diagnostics in the future. The current waveform would tell you if the motor is turning/locked/freewheeling/electrically open/whatever.

You could also compare the amount of current the motor draws with your Power Probe to what it draws with the AC auto amp? Just an idea.

I think your instinct to use some kind of substitute load is right on. There's no resistance spec for this thing, of course, so you'll have to use your best judgement on how big a load. Maybe one or two amps?

My money is on a bad water valve.

Thanks! I think you're gonna be right about this. I'm a classic over-thinker, so these ones kill me.

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All correct, except for there is no fuse here. The valve goes directly to the amp. Right before I left yesterday I powered the valve with PP and let the truck idle while I cleaned up to see if I had heat flow through and I still didn't. I don't know how long that motor has to turn to open but I do think it's the valve.

With there being no fuse, what if it did internally short or the gears got jammed?

Since both wires are grounded normally, if I tried to provide power going from B+ to one side of the valve, my light would just light up, right? I don't think it would make the motor work.

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Tutti57 wrote: Right before I left yesterday I powered the valve with PP and let the truck idle while I cleaned up to see if I had heat flow through and I still didn't. I don't know how long that motor has to turn to open but I do think it's the valve.

Does this look like the valve in question?



I was trying to get an idea of what kind of gear ratio it uses to turn the valve, but I can't really tell from pictures. :silly: Thought that might give us an idea of how long it takes to move the valve.

Speaking of, there's no position sensor in the valve, right? So I figure the AC auto amp has to be monitoring current on that driver circuit to make sure it doesn't strip the gears in the valve. Kinda like Chrysler/Dodge/Jeep HVAC actuators.

While I'm thinking out loud... Does the presence of the valve require special bleeding procedures? Or, can I just use my vacuum filler like normal?

Yep, that's the one. I have not bled one of these with my vacuum tool since I've gotten it, so I'm not sure, but I think I would do koeo with heat on 90* to make sure the valve is open. Using the coolant funnel set up can be tough with these. We will usually try to lift the front of the truck up while doing it. I got the vacuum tool for these dang things and haven't needed it yet cause we don't see a ton of them. Same set up on the titans.

I will likely be replacing the valve and I'll dismantle it to see what is in there exactly.

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Well it was the valve. I'll take the old one apart in a bit.

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Fixed another one.

Thanks fellas. This is a common issue on armadas and titans and yes I go right for those hoses. You can put your hand on them and feel that one is hot and one is cooler. The other tech claimed that he did this but I don't believe him since the valve wasn't working and he said that it got better after his heater core back flush but it was straight cold air when I got it.

Here are the guts of the valve.

How would you have gone about this if you found one side of the hose cold, then 10v at the connector? I feel like I would have questioned that 10v and not known if it was ok or not if I did this all over again.

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So that doesn't function like the old Ford vacuum control valves that only shut off coolant flow for max A/C?

Good find, keep up the good work!

That looks like a goofy setup. :lol: No wonder those break all the time.

Maybe I'm way off? But I still think a current waveform would be useful on these, depending on the nature of the failure. I'm imagining a known good is something like a window motor. Steady current with the valve turning, then high draw when it reaches the stops.

Mail me this valve and I'll play with it.

Tyler wrote: Maybe I'm way off? But I still think a current waveform would be useful on these, depending on the nature of the failure. I'm imagining a known good is something like a window motor. Steady current with the valve turning, then high draw when it reaches the stops.

Sounds reasonable. You'll see the commutator segments if it's turning. And if the current doesn't go up the gears are likely stripped.

While I had a '12 Armada in for wheel bearings, I took the opportunity to check out the heater control valve. The valve itself looks to be slightly different? But the general design is probably very similar.



Red is motor current. 100mV/A. Blue and green are the two wires at the motor connector. This motor doesn't draw nearly as much current as I thought it would?

Here's zoomed in on the current waveform:



Steady state, the motor draws around 340mA. If you're substitute load testing this motor, something like a headlight would be way too much. :lol: A 194 bulb would be perfect.

Here's voltage on one of the control wires with the motor turning:



12-something volts. Took this with the engine running. Not sure if that makes a difference? :huh:

Awesome. Glad to read this and good reminder to be careful with the types of substituted loads too.

Your 12v makes sense I guess, since the battery would probably be around 14v running. Mine at 10v koeo had 12v, so the same 2v difference?