# 2007 Pathfinder no rear heat and intermittent front heat



## hefeighteen (May 13, 2017)

Hi all

Two separate issues I believe. Front auto HVAC setup, on cold mornings after truck is warmed up, heat is luke warm at best, often just cold. If I use recirculate mode it gets piping hot like it used to. So I think either the heater core isn’t heating air fully and I need coolant (it’s a little low but not crazy low), I have an air bubble, OR, the door that lets/blocks outside air in is stuck open. I’m leaning toward this last option because I have a loud noise from behind the glove box sometimes when changing HVAC setting that sounds like a door trying to move that can’t. Lasts about 4-5 seconds. Thoughts?

Second issue is rear heat. I’ve been told this is a separate electric heater, and that coolant doesn’t go back there. I see two metal lines going back there and I believe those are AC so that theory checks out. The blower works fine, it just blows cold air no matter where the temp knob is. It appears the air intake for that blower is in the cargo area closest to the lift gate. I looked under the hood and inside the glove box for fuses or relays for rear heater but I only see rear blower fuses. So aside from opening that cargo area trim panel, which looks like a pain, and replacing the heater, I don’t know how else to troubleshoot. Any ideas?

Also if anyone has the FSM, or access to it, for the 2007 I’d love to get my hands on it. Let me know.

Dan


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## smj999smj (Jan 1, 2006)

Free, downloadable, factory service manuals can be obtained at Nico CLub's site (Google it).

The rear heater is not electric. The A/C lines run behind the passenger side finisher. The aluminum pipes you see running along the passenger side frame rail carry coolant. If you are not the original owner, you may want to inspect those lines to make sure they where not cut and capped off, as some people did this when coolant leaks occurred at one of the lines rather than replace or repair the lines. By the sound of your concern, the most likely cause for both issues in trapped air in the system, which is pretty common on these vehicles. Other possibilities include a stuck open thermostat or a bad heater pump. If the coolant gauge needle sits on the lower end of the spectrum most of the time, I would suspect that it is stuck open, at least partially, causing the coolant not to get hot enough. The heater pump is a small, electric pump used to help push the coolant through the heater cores. It is located inside the engine compartment, mounted to a bracket attached to the firewall and sits just to the left of the power brake booster. It'll "T" between two heater hoses and will have two wires going to it; many people mistake it for a heater cock (control valve). They don't fail too often, but can. 
If the coolant is reaching proper temperature, I would try purging it, first. Make sure the coolant reservoir is topped off. Jack the front of the vehicle up as much as safely possible, or park on a steep hill (nose up). Start the engine and turn both front and rear heaters "on," set to maximum heat. Run the engine at 2500-3000 RPM for at least 10 minutes, checking the airflow temperature output from the vents. When hot air exits the vents both front and rear, you can turn the engine off and lower the vehicle (as applies). If after 20 minutes there is still cold air coming out of the vents, I would look for another problem other than trapped air. 
The recirc door operation can be viewed if you remove the glove box assembly. You may have a bad recirc mode door actuator; the actuator is not expensive (around $35), but you have to remove the dash in order to replace it properly.


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## hefeighteen (May 13, 2017)

Thanks for the quick reply and useful info. Good to know about the rear heater. I am the original owner, no lines have been cut. So I’ll have to get a bottle of coolant and try the purge. Anything special about which coolant to buy? The owner manual says special Nissan coolant, and when I attempted to buy some last week the chick at oreilly asked me if it was red or green and I couldn’t answer off the top of my head (it’s my wife’s truck). I looked yesterday and it’s green if I had to pick a color, but it’s pretty orangish green. Also trying to remember (now that I think about it) if the shop in town flushed coolant as part of their service this summer.

What other troubleshooting is available for that pump? A multimeter to check voltage? How else can you tell if it’s pumping?

So I dropped the lower glove box door down and looked around in there but didn’t see much other than the cabin air filter access. Do I need to take more apart to see the door action?  What does that door do? Is it spring loaded to one position and held in the other? Is it variable? I actually heard it doing something after I shut the car off yesterday, so I’m wondering how it works and what the symptoms would be.

Thanks again, and I’ll check out the FSM.


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## quadraria10 (Jul 6, 2010)

https://ownersmanuals2.com/make/nissan/pathfinder-2007-4196


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## hefeighteen (May 13, 2017)

Bump for any more insight into questions above. Door behind dash, coolant specs, and troubleshooting pump.


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## hefeighteen (May 13, 2017)

So I have some more info. I parked on a hill and added coolant to the radiator, left both caps off and ran the engine for a few minutes. I believe that was the "burping" method I read, though now that I look at the replies to this thread no one mentioned the caps coming off. As you would imagine lots of coolant and bubbles came out, and I decided it was just making a mess and wasting coolant so I shut it off, capped the rad and res and ran it some more. With the caps on, where are the bubbles coming out of the system? The reservoir? What does parking on a hill do?

The heat in the front got blistering hot, but that's not necessarily a big change. The front heat has been intermittent, so sometimes it's hot as hell, and other random times it just goes cold. But this was a good start. The rear heat was still blowing ice cold. I tried front and rear controls for it, and tried switching to full cold and back. I got down behind the truck and touched the metal lines going to the right rear corner which I now know are for the heat, and one was hot, the other was not. So I thought I had diagnosed a blocked heater in the back. But then I got in the truck and surprise- the rear heat was no longer ice cold, but rather warm. Not hot, but warm. I sat there a few minutes longer and it got cooler over time.

I tried holding and touching the coolant pump under the hood with the engine running to see if I could tell if it was on, and aside from a periodic surging vibration kinda feel, I couldn't tell. Also couldn't tell if that vib was even coming from that pump or just being transmitted from elsewhere.

One thing I found odd during all this was the lower radiator hose never got hot. I probably had the truck running for over 30 minutes, it was plenty warm, and all the other coolant lines I touched were hot (minus that one in the back). But the lower hose was cold. Isn't that odd?

The temp gauge during all this started low, got to about the 4 o'clock position and stayed there the whole time, which is normal for this vehicle. So I think the thermostat is opening at the right temp.

My next step, at least for the rear heat, was to remove the lines from underneath and force water into the fittings to maybe knock loose whatever gunk might be in there. I suppose I'll have to drain quite a bit of coolant in the process, but seems like the only way to get some pressure through that thing. Is there a better way?

I don't have a next step for the front other than to let the wife drive it a few more days and see what she says about the heat. Any more help would be greatly appreciated.


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## smj999smj (Jan 1, 2006)

Nissan never had red coolant (that was Toyota). Green coolant, actually Pentosin Pentafrost A2, was the factory fill and is my preference, but any green or "works with all colors" anti-freeze on the market will work. In 2010, Nissan started using blue coolant, Pentosin Pentafrost A3, which has a longer service life than the green but is compatible, nonetheless. 
The radiator cap should only be removed for filling the radiator when the engine is cold and not running. There should be no spring on the radiator cap, unlike the reservoir cap, which is the pressure cap for the coolant system. Parking the vehicle uphill, or jacking the nose up, helps allow any air bubbles from the heater cores to work their way up to the front of the system where they can be purged out into the reservoir. While it's possible that you have a restriction in the rear heater core, it's more likely you just have an air pocket trapped in it. As far as the heater pump, there "may" be a test procedure in the FSM, but I'm not aware of one off the top of my head. You could try holding it and unplugging the connector for it and plug it back in to see if you notice a difference.
The recirc mode door, like all of the other HVAC mode doors, uses an electric motor (mode door actuator) to position it, controlled by the heater control head unit. You have to remove the whole glove box assembly (which includes that part of the dash it's mounted into) in order to see the mode door operate.


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