Neus68

My wife drove the 09 RDX to work yesterday. It has been an extra car while we wait for my daughter to turn 16...her first car. It was chilly here in the morning and she told me that the car wasnt blowing hot air...simply mild. Then once the afternoon hit, it was in the 80s and no AC either. You can hear the blend door closing. Could the control be the culprit causing the system not to trigger? I swapped out the AC Relays, but nothing changed on either front. I also put a meter on the main relay, where I was getting 14v positive on two poles, and 14v negative on two poles. No engine fans either. The air coming out of the vents was basically outside air, even when the controls were set to High. That is why I am leaning toward the controls themselves. Any thought would be greatly appreciated!

justnspace

iTrader: (1)

the only way to know is to test the controls...taking it apart and putting electrical current through them to see if they work .
perhaps the brass contacts are oxidized? perhaps they just need to be cleaned?

I guessed on my 2006 TL...and just ordered a used replacement control switch thingy from ebay for less than $20. it switches from heat to a/c. and now I can defrost again.

Neus68

Thanks for the input. Happen to have a schematic or a pin out for the controls? Just thought I would make sure that I am getting power out (or ground) on whichever the triggers need to be.
Thanks!

WellHellWtvr215

Given you mentioned you could hear the blend door operating, I'm leaning towards it not being the controls. I believe you may have a couple issues, it's just narrowing down which ones...

Firstly, how long has the car been sitting? You said it's an extra car, has it been hanging out a while or is it driven regularly? Did she happen to glance at the coolant gauge while driving? If it's lower than roughly half way, after driving a while, the thermostat is stuck open and not allowing the coolant to actually get warm. This could also effect the AC not turning on as many cars take reading from the Engine Coolant Temp sensor to even allow the AC to turn on. If it sees the coolant as cold, it won't turn the AC on.

Honestly, I have a feeling that (1) it's low on coolant and the system needs to be bled (or thermostat issue), that would fix the no heat issue. And (2) you're going to have to get some pressure gauges on the AC lines to see if it's even full of refrigerant.

If the refrigerant is up to spec, the pressures should be somewhere between 20-50 psi low side and roughly twice ambient temp +50 psi on the high side (usually between 150-250 psi). They should also move up and down with AC turned on. You said the AC relays didn't solve anything, so I'm leaning towards either the refrigerant is low and the fail-safe for AC systems when it's low is to not turn on at all, or the AC compressor has gone out. This would also effect the fans not turning on as the vehicle sees no large load added so it's not turning them on.

-Shane

Neus68

Shane, thank you for taking the time for such a detailed response. I will take the car for a ride at lunch to see what the temperature reads. Yes, the car sits for a few weeks at a time depending on the weather. The wife has been driving it on rainy days so she doesnt have to put the top on the Jeep. What triggers the engine fans to come on with the AC? Is it controlled by a relay, or controlled by the compressor? Since they arent coming on, I thought it was upstream of the compressor.

WellHellWtvr215

No problem man, hopefully it narrows down the issues.

There are two fans for our cars. One turns on only when it's required to lower the coolant temp, such as sitting in traffic on a hot day. The second one turns on when the AC is turned on since this added load will cause the engine to work harder, thus creating more heat. Both of these fans are regulated by relays in the engine compartment. Basically, looking at a wiring diagram would likely show a power wire going to the AC compressor, but the same power wire also going to the relay to turn the fan on, if that makes sense. Again, since you said switching relays didn't change anything, it's likely they're both perfectly fine.

It's really just identifying why the AC isn't turning on, as basically since the system is likely either not seeing pressure or the compressor isn't working, in turn not turning on the fan. Ultimately, no AC operation also means no fan operation, and vice-versa.

Neus68

Shane, Thanks again. I will probably focus on one problem at a time on this since it sounds like they are unrelated. And whose to tell me that my wife isnt always right! well, at least, regarding the heating issue. I will go for a ride now. Thank you!

Neus68

So, I will have to say it...but dont tell anyone...my wife was right. I just went for a drive until both fans came on. My IR temp gun was showing 200 on the block. On my drive, no matter what I did, the air coming out of the vents did not change. The internal fan works well, but no matter AC or not, Hi or Low temp...the same temperature of air comes out. WEIRD. I dropped the glove box and noticed a white lever attached to an actuator that would move in a two step process once at 73 degrees, and again at 77 degrees. Could it be a stuck recirculation door? Needless to say, I am going to guess that the AC is a whole different problem...I guess I get to focus on the heat since its September.

Neus68

And to add, both sides operate the same temperature whether set to "dual" or not.

WellHellWtvr215

Recirculation is primarily used to increase efficiency in different modes: recirc closed is used with AC to keep cooler air in the cabin cool; you can think of it as it's much more efficient to keep air cold than it is to continuously cool down fresh, 90+ degree air. Alternatively, recirc open is used with heat as keeping hot air in the cabin (recirculating) increases humidity. Ultimately, regardless of door orientation, the heat should still be operating.

Did you by chance check the level of the coolant? Also, given you have a temp gun, check the temperatures of the top and bottom radiator hoses. After the thermostat opens, the temps of them should be near identical, maybe give or take 10-ish degrees. While you're at it, there are 2 more smaller hoses that go into the fire wall, almost directly behind the turbo. Check the temperature of these two hoses as well. With proper coolant circulation into the heater core, these two hoses should be identical in temp.

Neus68

Well, the coolant is full including the reservoir. I went for another drive and there is about a 10 degree difference between the upper and lower radiator hoses, and about a 40 degree jump between the heater core hoses. 120 to 160. Guessing there is lack of flow or a bubble in the heater core. Thoughts?

thoiboi

Try to burp the coolant system

Neus68

Well, burping is an easy one to do once the car cools down a little! Will see!

WellHellWtvr215

The temp difference between the heater core hoses tells me there's air trapped there. Easiest thing to do is take the colder hose off for even just 2-3 seconds. Once the air is out, coolant will start gushing out and then all you do is pop it back on.

Likely that will give you nice hot heat again, fingers crossed anyway

Neus68

Well Shane and Thoiboi were correct! I went old school and simply ran it without the cap on for a while then revving the engine up; to 3k. It was noticeable once the bubble went free, I could feel the heat even with the fan off. The heat coming out is about 105, but that was with it at idle. I would assume that it will get warmer once the coolant circulates a little more. I checked the heater core hoses and they were about 10 degrees different. I cant thank you enough! Now to do the field coil over the winter, along with the radiator before it fails!

WellHellWtvr215

Just an after-the-fact FYI for anyone who comes across this post: for those of you who do anything coolant related to your vehicles, the video above shows what's called a "spill-free funnel" (I prefer and own the one from the company Lisle) and it's absolutely the BEST thing you can buy for yourself (like $25 off amazon). I've been in the auto industry for 5 years now and use it on an almost daily basis.

Attach that in place of where the radiator cap goes, keep filling until it stays about half full, and then run your car for 10-20 minutes with the heat on high. It makes the highest point in the system the funnel so air wants to go up and out, while allowing coolant in its place. Once you have hot heat out the vents, it's about 98% likely you have absolutely bled the system and you'll have no issues.

-Shane

Neus68

Well, I figured I would post an update from today. Now that it is colder here in Indiana, I went for a ride in the RDX. The heat was barely warm...but a little warm, not hot. So I figured this would be a good time to do the radiator, upper and lower hoses, and the thermostat. Piece of cake job and no issues. Started back up, still no heat. Tried to run water through the heater core with the garden hose, no deal...not even a little. So I started to look to see where the hoses went through the firewall. And what did I find? Yes, a valve mounted to the firewall that had a cable connected to hit that had fallen off. It appears that this is a valve that stops the water from getting to the heater core. Once I moved the valve, we have HOT air! I figured I would post this just in case someone else has the issue.
Thanks!

CSmoney28