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Discussion Starter #1
Do the AC and radiator fans ALWAYS run in tandem (on and off at the exact same times) in Honda Pilots? I have a 2006.

Here's the scenario:

- The AC system won't hold refrigerant, and I know there's a much larger problem here. When the AC system is "dry" (no refrigerant), the AC fan AND compressor don't kick on when you turn on the AC inside the cabin (just the blower motor). This makes sense to me since there's no pressure/refrigerant in the system.

- While monitoring the fans in the engine compartment, I panicked a bit when I thought the radiator fan wasn't running either. In other words, I thought the two fans ran independent of each other. So I expect the AC cooling fan not to run when the AC is either off inside the cabin (or completely absent of refrigerant if turned on), but I DO expect the radiator fan to run by itself independently of the AC fan.

- With engine running, I recharged the AC system tonight with canned refrigerant and stop leak (cabin AC on), and the compressor quickly kicked on as I was filling it, as did the AC and radiator fan at the exact same time. I expected the AC fan and compressor to kick on since I'm charging it, but I didn't expect the radiator fan to come on at the exact same time. This made me think both fans are linked (or timed) together. No big deal.

- To confirm this, I then turned off my AC inside the cabin after being recharged, and both fans immediately turned off exactly at the same time. I was now worried about the radiator fan not working independently at this point. The engine temp stays a smidge under the "halfway point" gauge on the dash, and there are no other warning indicators. No history of radiator/fan/overheating problems in the 5 years I've had it. Fuses and relays seem ok.

- After the recharge and continuing to let the engine run for about 10 more minutes with the AC off inside the cabin (therefore I expect the AC fan to definitely be off), the radiator fan AND the AC fan kicked on together for a really brief time, and then turned off together. I was glad the radiator fan kicked on, but I expected JUST the radiator fan to kick on/off for a brief moment, not BOTH, since the AC was turned off.

So are they always linked to run in tandem? Will the radiator fan will kick on as usual when needed by the engine due to temp, and also kick on the AC fan even if the AC is turned off in the cabin (or devoid of refrigerant)? I know when you have the AC on in the cabin, the AC fan needs to run, but it seems the two will always run regardless of the scenario. It just seemed odd to me, so I'm not sure if it's a Honda thing, a Pilot thing, or this is normal on most cars and I just haven't noticed it since I'm now hyper-aware due to my AC problems.

I'm a total noob, but trying to learn more about cars, so please be kind towards me, haha. Thanks in advance.
 

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Welcome to the forums even if you are "learning" you are in the right direction show respect others will respect you :) as for the fans i went out tonight to look at the fans on my 06 since i never bothered and they do come on at the same time. Get your AC fixed soon as you can cause if you noticed when running the heat the ac clicks on automatically thus turning on you rad fan.
Post back if you have questions on how to find the leek there are some really great users here that have alot of knowledge ... make them feel warm and fuzzy and it's like attracting bees to honey lol :)

Again welcome
 

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Discussion Starter #3
Welcome to the forums even if you are "learning" you are in the right direction show respect others will respect you :) as for the fans i went out tonight to look at the fans on my 06 since i never bothered and they do come on at the same time. Get your AC fixed soon as you can cause if you noticed when running the heat the ac clicks on automatically thus turning on you rad fan.
Post back if you have questions on how to find the leek there are some really great users here that have alot of knowledge ... make them feel warm and fuzzy and it's like attracting bees to honey lol :)

Again welcome
Hey there! Thanks for the warm welcome. I was raised an Army brat, so my default is to always show respect until otherwise warranted! ? Thank you so much for taking the time out of your day to look at your car to help a stranger on the internet, that's very kind of you and the fact that yours does it too puts my mind at ease a lot!

I fixate on the weirdest things sometimes, like the fan situation. I'm an IT guy, so cars typically aren't my forte, but I'm learning. My '06 Pilot has 117k miles on it, so some normal wear and tear is starting to show, but otherwise has been mechanically sound. I do need to service the transmission and differential though, I haven't done that since I've owned it. :censored: I did replace the timing belt at 89k when I bought it though, just to be safe.

The problem with the AC not keeping refrigerant is a whole other story though. I'm a very detailed oriented person, so when I first was drafting my original post, it was a lot longer. It basically involves two techs, and I'm not quite sure if one of them did something, or if it was my fault when servicing the cabin filter and blower motor (but I wouldn't think that would cause it).
 

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Both fan relay coils are tied together and each ground by one of two routes; 1) through C282 if the A/C is switched on AND the A/C pressure switch is closed due to proper Freon pressure AND the ECU relay control provide ground sensing. or 2) through C114 if the ECT switch closes when the coolant reaches 194*F providing a direct ground independent of the ECU thought G101. The Fan Timer Unit provides the power to the relay coils.



134068
 

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somewhere on the forums is the downloadable service manual ..being a fellow IT guru I'm sure you already know how to look for it :) .. couple great threads on How too's for the tranny fluid and rear diff ..
 

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Discussion Starter #6
Both fan relay coils are tied together and each ground by one of two routes; 1) through C282 if the A/C is switched on AND the A/C pressure switch is closed due to proper Freon pressure AND the ECU relay control provide ground sensing. or 2) through C114 if the ECT switch closes when the coolant reaches 194*F providing a direct ground independent of the ECU thought G101. The Fan Timer Unit provides the power to the relay coils.



View attachment 134068
This is very interesting, thank you! I never thought to look for a circuit/wiring diagram for this issue!
 

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Discussion Starter #7
somewhere on the forums is the downloadable service manual ..being a fellow IT guru I'm sure you already know how to look for it :) .. couple great threads on How too's for the tranny fluid and rear diff ..
Indeed, I just stumbled across this forum for this first time tonight. Lots of good info here, thanks guys.
 

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Discussion Starter #8 (Edited)
This was my original backstory I left out, out of fear of being too long, but my original post was a bit lengthy anyways!

--------

The AC problem mushroomed into a nuclear cloud from a seemingly routine trip to the shop. Fun fact, I also live in Florida, the land of perpetual summer.

I thought my alternator was bad, so I took it to my corner garage guy of 5 years, but it was just the battery (he had replaced the alternator 2 or 3 years ago, so I thought that may have been the problem again).

1.) I also told my mechanic my AC was really smelly lately, almost like burned wires (or oil). He checked my AC and he said it was "bubbling up a bit around the Schrader valves", but otherwise seemed fine. He wanted $175 to change out the Schrader valves, so I said no thanks, not at this time. He didn't want to charge me to recharge the AC, as he said it might not hold refrigerant because of the faulty Schrader valves and didn't want me to pay for that. It was blowing cool (like it had been for a long while), but not cold, and was still smelly when I left the shop. I wasn't educated enough at this point to ask for pressure readings. I appreciated the honesty though.

2.) A week later, while out and about, I went to get my oil changed at another place since I felt lazy and didn't want to do it myself. I know the guy well, and trust him. I told him about #1, and he pointed out I had leaves coming out of my cabin filter, and saw a few in the blower motor, and told me to change the cabin filter and clean the blower motor because that's probably causing the smell. He said he had a similar issue with his car (I didn't even think of this and my mechanic from #1 never mentioned this, so I felt silly, but also wondered how in depth he really checked the first time around). After the oil change, I had him suck out the old refrigerant and recharge the AC system to where the pressure readings were 150 high/30 low, and he said we'll keep an eye on the readings to see if there's a leak in the coming weeks, but said he didn't think anything was wrong with the Schrader valves at all. The compressor was kicking on, as well as the AC fan, and the air was ice cold after the recharge. However, it did take a lot of refrigerant, and he pointed out his gauge system "bubble window" and how much refrigerant it was taking in (which was quite a bit).

3.) About 3 days later, with the help of a friend who was a Marine Corps mechanic, we then removed my glovebox, the cross bar, and passenger floor/trim panel to change out my cabin filter and clean the blower motor. We sucked out the leaves and other crud with a shop vac, and gently cleaned the evaporator core with a soft, clean paintbrush (to get out the dog hair the previous owner had). The new cabin filter was put in. The blower motor was taken out and we cleaned some leaves out of that too. We put everything back and the blower motor worked fine. The air smelled better, but was not very cool again despite the recharge a few days before. I'm pretty certain we didn't do anything bad/wrong, it was easy despite the cramped space (and he's pretty dang handy with cars as you could imagine from his training).

4.) I checked the AC again a few days later after the filter/blower deal, and noticed that now it wasn't cold at all. I waited a few days because it's actually been in the 50's here and enjoyed having the windows down for our 10 minutes of "winter".

5.) I go back to my mechanic from #1, tell him everything up to this point (#2 through #4), and he now tells me there is no freon at all, and the evaporator core is bad. He quoted me $985 to fix it. He then says "yea, it's bone dry, and we refilled it last time so that's a sign"..........even though he didn't actually recharge it then because he thought it would leak due to the Schrader valves! Now I'm a bit skeptical of his memory and diagnostic skills despite his prior, non-AC work for me being spot-on. I also know it's a labor intensive job to change out that core. The parts aren't that much (in comparison).

- From the novel above, is there something I possibly did to make this worse when changing out the filter and blower motor? It has nothing to do with the closed refrigerant system, so I'm leaning towards "bad coincidence"? Another possibility might be from Mechanic in #1, or maybe #2? That will be a lot harder to figure out though. I just think the whole timing on this is really odd.

From smelly AC -> refrigerant recharge -> swap dirty filter/clean blower -> no refrigerant at all now. WTF?

I'm not suggesting sabotage, but I'm wondering if #1 was clueless with AC's and made it worse or misdiagnosed, or #2 overcharged it....but either way, I'm potentially looking at a $1000+ repair, and a massive AC fix is definitely out of my comfort zone. I'm going for a 3rd opinion on Monday to a shop who does a free inspection and uses dye. I think that's best course of action in terms of getting a more realistic prognosis of what's really going on.

Any suggestions? Cautions? I read that AC repairs can range from $600-$3000+. It seems they're never cheap to fix!
 

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I doubt you damaged anything. It is certainly possible you have a leak in the evap core, but I'd want a UV dye test for that.

The compressor oil in these stinks, and if you have a strong smell of burnt oil when running the fan, that is a plausible sign you have an evap leak.... as the oil leaks out on the evap core and the fan blows through it.

Schrader valves leaking is a very common issue, the o-ring on the valve ages and stops sealing. The telltale sign is oil around the fitting on the high or low pressure side. When one fails you replace both. It isnt hard, but you need to empty the system. You should ensure dust caps are always kept on these fittings, they got lost over time, and this causes dirt to accumulate around the seal and will ruin it when it is used.

I learned quickly how expensive it is for AC work on a car, so I purchased a gauge/vacuum kit on Amazon for $120, and figured if it only worked one time it would pay for itself. I buy the freon cheap at Walmart or eBay (plain R134a, nothing else in there). I have used it 4 or 5 times now, on mine and relatives vehicles, and it just keeps working like a champ. https://www.amazon.com/gp/product/B00SZ4QFW0

Here is what I would do.

1. Vent whatever is in there.
2. Replace both schrader valves.
3. Pull a vacuum per the instructions to remove all moisture from the system. When you put the vacuum, you then let it sit and watch for a leakdown. If it leaks down, you have a failure in some component. A this point you have only spent $120 plus a few bucks for valves, and you have confirmed the leak.
4. If there is no leak, then I find the total system capacity by weight of the AC system, then just put that in using cans. This makes it REALLY easy to get the perfect refrigerant amount, even if you don't know how to read gauges (which isnt hard, there are youtubes for how to do this based on ambient temps)
5. If there is a leak, then I'd buy a can of UV dye filled refrigerant, and fill according to their instructions back to capacity of the system, then use a UV light to try and detect the location of the leak, along the hoses, at connection points under the hood, and if you can get into the evap, look there.

A good mechanic will have a refrigerant "sniffer" and can identify pretty quickly if it is the evap core or not.

Owning the pump and gauge set is cheap to me, and helps me be much more informed should I pay someone to repair the system. And lets me fix simple things like schrader valve leaks for next to no cost.
 
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Discussion Starter #10 (Edited)
I doubt you damaged anything. It is certainly possible you have a leak in the evap core, but I'd want a UV dye test for that.

The compressor oil in these stinks, and if you have a strong smell of burnt oil when running the fan, that is a plausible sign you have an evap leak.... as the oil leaks out on the evap core and the fan blows through it.

Schrader valves leaking is a very common issue, the o-ring on the valve ages and stops sealing. The telltale sign is oil around the fitting on the high or low pressure side. When one fails you replace both. It isnt hard, but you need to empty the system. You should ensure dust caps are always kept on these fittings, they got lost over time, and this causes dirt to accumulate around the seal and will ruin it when it is used.

I learned quickly how expensive it is for AC work on a car, so I purchased a gauge/vacuum kit on Amazon for $120, and figured if it only worked one time it would pay for itself. I buy the freon cheap at Walmart or eBay (plain R134a, nothing else in there). I have used it 4 or 5 times now, on mine and relatives vehicles, and it just keeps working like a champ. https://www.amazon.com/gp/product/B00SZ4QFW0

Here is what I would do.

1. Vent whatever is in there.
2. Replace both schrader valves.
3. Pull a vacuum per the instructions to remove all moisture from the system. When you put the vacuum, you then let it sit and watch for a leakdown. If it leaks down, you have a failure in some component. A this point you have only spent $120 plus a few bucks for valves, and you have confirmed the leak.
4. If there is no leak, then I find the total system capacity by weight of the AC system, then just put that in using cans. This makes it REALLY easy to get the perfect refrigerant amount, even if you don't know how to read gauges (which isnt hard, there are youtubes for how to do this based on ambient temps)
5. If there is a leak, then I'd buy a can of UV dye filled refrigerant, and fill according to their instructions back to capacity of the system, then use a UV light to try and detect the location of the leak, along the hoses, at connection points under the hood, and if you can get into the evap, look there.

A good mechanic will have a refrigerant "sniffer" and can identify pretty quickly if it is the evap core or not.

Owning the pump and gauge set is cheap to me, and helps me be much more informed should I pay someone to repair the system. And lets me fix simple things like schrader valve leaks for next to no cost.
Thanks, Boom! That's some really good info, and I never thought of getting the vac myself, what you said really makes sense too in regards for paying for itself (and you can always top off/recharge fully yourself going forward). That's also some really good info about the oil smell.

What do you mean by "watch for a leakdown"? Like I'm actually looking to see if something is leaking from valves/lines? Or is that referring to something the vac is doing?

A follow up question I thought of, that might be independent of all this. I always noticed there is a slight breeze coming through the AC vents, even if the unit is fully powered off. What could be the cause of that? It was chilly (for FL) this morning, about 50, and I felt like I had the AC on a low setting, an obvious breeze was passing through. This has been going on for a long time though, but I didn't think it was anything serious.

Again, appreciate the help.
 

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What do you mean by "watch for a leakdown"? Like I'm actually looking to see if something is leaking from valves/lines? Or is that referring to something the vac is doing?
When you pull a vacuum on a vehicle AC system, you do this primarily to remove all traces of moisture. However, once you pull the vacuum for the specified amount of time, you turn the pump off and let it sit, for 15-45 minutes, and watch the needle, it should not move and the same amount of vacuum should stay constant. If you lose vacuum, then you have a leak, and you begin leak detection steps. If the vacuum holds, then it is unlikely that you have any leaks in the system and you can begin filling it with refrigerant. The CAVEAT to this is the schrader valves. When doing the vacuum leak test - they are open because the gauges are connected, so a leak at these valves would not be detected. That's why it's a good idea to just replace them anytime you are going to evacuate the entire system.

A follow up question I thought of, that might be independent of all this. I always noticed there is a slight breeze coming through the AC vents, even if the unit is fully powered off. What could be the cause of that? It was chilly (for FL) this morning, about 50, and I felt like I had the AC on a low setting, an obvious breeze was passing through. This has been going on for a long time though, but I didn't think it was anything serious.
If you mean while driving, this is normal if re-circ is not engaged, as positive wind pressure from driving will always allow air flow through the system. If recirc is set, then the air intake should not be from fresh air, but from recirculated air, so any external air pressure from the fresh air duct should not matter (unless you have a blend door issue)
 

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Both fan relay coils are tied together and each ground by one of two routes; 1) through C282 if the A/C is switched on AND the A/C pressure switch is closed due to proper Freon pressure AND the ECU relay control provide ground sensing. or 2) through C114 if the ECT switch closes when the coolant reaches 194*F providing a direct ground independent of the ECU thought G101. The Fan Timer Unit provides the power to the relay coils.



View attachment 134068
This is great, I love this schematic diagram. How can one get the the complete electrical schematic?
 

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I think I have what you're looking for, but first I'd be curious to see your picture of what a Pilot in Nigeria looks like.
 
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