On my DX model...(Canadian base model), when I put it on MAX AC, the radiator/condenser fan stay on all the time.

What happens when you switch it over to MAX AC?

 

Max A/C didn't have this effect on my '07 EX-L. Believe me, we have to run on recirc/max mode all the time here in the summer.

 

Looks like a great mod. Nice writeup.

 

atoner,
This is a great mod! How hard is this to do, I mean, What are the chances that I can screw this up, and break something else?

I too have found that mid-day Florida heat is too much for the Ody when driving slow or idling.

I really like the idea of putting this mod on a switch, then pretty much all of the caveats you mentioned would be moot. One could engage the switch when driving slow, and disengage when not needed at highway speeds, or night time.

I use my remote starter several times a day, and when idling in mid day heat, the van only begins to cool down, until we starting rolling. With this mod, maybe the van will cool down faster when idling.

 

Awesome mod.

Here's a thought. What if you could take input from the speed sensor and the light sensor and only do this while say you're below 25 MPH and in day time. Then, it would be a perfect mod but that's easier said than done.

 

I tried the link to the website with the relay, and I get this:

"No records match your search criteria"

Digi-Key

 

Dumb question, why not just take it off auto and manually turn up the fan speed? :huh:

 

They're talking about the radiator fans not the ones inside the cabin. I have noticed the problem being discussed personally. On very very hot days, even if you turn on the A/C at full blast and turn up the fan all the way and you're stuck in traffic, there isn't that much cold air coming out. Once you start doing 40+ mph, all's well in odyland.

 

So this mod manually turns the radiator/condenser fans ON to generate air flow for times when the van is hardly moving forward?

 

I read the DIY pdf file, I agree that it'd be better to install a switch on the dash that is under your control, i.e., turning it ON ONLY when you sit idle.
Otherwise your fan lifespan will be shortened quickly.

Anyway, this mod proves that this works! All you have to do is to install a switch somewhere.
Actually you can use the same mode but run the wire to the cabin and install a switch to ground.

The BMW engineers are smarter when it comes to this, after the vehicle reaches certain speed (such as above 15-20 mph or something like that), the Aux fan is shut off to prevent wear/tear on the Aux Fan.

 

Does anyone have schematics for the speedometer? I'm guessing there's a digital bus which communicates to the instrument cluster (not easy to tap off a signal). There's a chance we could tap off an analog signal at the speedometer itself.

It may also be possible to tap off from the speed sensors at the wheels. Again, more effort that I wanted to put into the initial mod.

Now that it has cooled off here in FL, I'm going to disable the mod for the winter.

I would sleep better if I knew the fan wasn't coming on at highway speeds.

On my last car, I installed a switch under the dash to engage both fans at high speed. This was useful for the A/C at low vehicle speeds and to cooling off the engine bay if I needed to do work, but with the engine off it'd kill the battery quickly.

 

I just wanted to report back that I've installed the fan mod for the 3rd summer with no ill effects. I'm still getting a fantastic improvement in cooling for city driving, idling in parking lots, etc. The AC cools down the vehicle much faster with the mod installed. I've had no issues with the radiator fans, cooling relays, etc.

For the past two years I've installed the relay around early June and taken it off around October.

Adam

 

This is interesting because in my 2007 Ody LX, once the AC button is pressed On, the Low-Speed Feature is on (both Condenser and Rad Fan run at low speed). Maybe the O.P.'s relay failed to work to start with??? New relay is $4 at dealer.

Here is the schematic of Hi vs Lo Fan Realys:

 

As I described in my original PDF, my fans did behave as you state: both on low when the AC is on. Low speed isn't enough for cold AC if the van is stopped. I suspected this when the air was dramatically cooler once I got up to ~ 40 mph. That's what triggered the idea to have the fans come on fast with the AC.

 

Interesting...

If you look at the electrical circuit, "FAN LO" from PCM triggers the "AC Condenser Relay", sending 12 V to both fans (the 5-prong relay default setting is current flowing from "1" to "4"). Now both fans are connected in series, this is why both of them run slowly as designed.

When the PCM sends "FAN HI" signal (when engine temp is too hot) to "Radiator Fan Relay", this does 2 things:
1. Uncoupling the 5-prong relay so the Condenser Fan stops.
2. 12V is sent directly to "Rad Fan" itself, therefore "Rad Fan" runs at HI speed.

PS: Although one fan is called "Condenser", and the other "Rad Fan", they sit side by side, so functionally, they should be called Aux Fan and simply runs LO or HI, and that is it. This is the terminology used in BMW, Volvo etc.
By calling these different names, Honda engineers made things more confusing for people.

 

The other way to do this mod (so Aux Fan can run on HI on demand by driver) is:
- Locate the 5-prong relay underneath the PS Reservoir.
- Find Pin #3 and run a ground wire so one can control it by grounding it.
Once you ground pin #3, Aux Fan runs on HI.

 

I would still love to find a way to make the fans come on high only when I'm stopped or, ideally, my vehicle speed is below ~30 mph. I haven't put much thought into this, but I wonder if there's a signal I could tap into. I'm guessing I could somehow get to the park signal from the shifter.

I've also noticed the headlights dim a bit when the fans are cycling due to the high instantaneous current drain. This may be another reason, in addition to fan and relay longevity, that Honda didn't bring the fans on high with the AC.

 

How about utilizing a shift light? disabling the mod when the RPM is above a certain threshold.

 

There is a signal for under 35 mph for the airbags.

 

Any idea where I can tap into this, preferably in a buffered location such than an issue with my modification won't interfere with the air bags? Thanks.

 

Just bought my 07 ex-l about a month ago. When I stop, idle and going slow my a/c just blow air. When driving the a/c is ice cold. When in park i pop the hood and the condenser fan is not even on. I can hear the fan trying to come on at idle and park. Will this mod work in my case? A friend mention that the fan clutch might be going out.

 

If working properly, I believe a stock '07 Odyssey should have both fans behind the radiator cycling on low-speed when the A/C compressor is on. If both of your fans do come on low-speed with the AC compressor and you're still having barely cool air when your Odyssey is stopped or going slow, this mod will help.

If you only see one fan coming on with the compressor, then you might have an issue with that fan or a relay. Do both fans come on high-speed if you let the engine warm up until the radiator needs air across it?

 

This is good info guys. I just had my "condenser" fan break on me and now after I installed the new one I havent seen it come on once even with the A/C on max.
The "radiator" fan comes on but the other one on the passenger side is just sitting there.
I guess an easy test would be to jump the relay and if it fires up then a new relay it is. If its not kicking in ill have to meter it out and figure out where im loosing my power to the fan.

 

So some suggestions on how you can modify the fan control to be fully automatic and "self aware" of it's surroundings.

I would imagine that we'd want to only active the fans on high when:

1. Vehicle speed is below say 25 MPH
2. Ambient temperature is above 85F

Materials needed to meet the above mentioned requirements:
1. User configurable ambient temperature switch (much like a thermostat). When temperature reaches above 85F then it closes the circuit to put the fans into high speed continuous mode
2. Air velocity sensor or switch. In the HVAC industry there is a switch called a "sail switch" that closes or opens a circuit if there is sufficient airflow. I would imagine that in our modern world that there would be something like that for measuring how much air is passing over the switch and open and close a circuit accordingly.

Just throwing out some ideas...

 

Before I replaced the relay, only the radiator fan come on when the van is in idle/park and the condenser doesn't. Went to the dealer and got 3 new relay. My dealer charge me $10 a pop. Replaced the relay and both fan came on while in park. That last about 30 second and the condenser fan stop (meaning there is a short somewhere to burn out the relay). Put the old relay back in it original place. Put one of the new relay into the low speed fan location (forgot which was the bad relay) and turn the a/c on. Again both fan work for about 30 second before the condenser fan went out. Turn the van off to put the original low speed relay back in. Rurn the van on and now both fan is not working. Hopefully I can get another relay for the radiator fan and that would solve at least one issue and let a mechanic trouble shoot the shortage of the condenser fan relay.

 

Before I replaced the relay, only the radiator fan come on when the van is in idle/park and the condenser doesn't. Went to the dealer and got 3 new relay. My dealer charge me $10 a pop. Replaced the relay and both fan came on while in park. That last about 30 second and the condenser fan stop (meaning there is a short somewhere to burn out the relay)...

Some tricks...
- Very easy to confuse the relays (old vs new), so use a sharpie to mark them before playing around with them.
- On the relay, there is a marking for the date of mfg, so you can use it to know which is old and new.

- Re condenser fan, search for posts by "Floyd", I believe his condenser fan disintegrated (plastic fan blew up), punching a hole in the rad ---> engine overheated ---> had to replace head gaskets ---> $$$.
But I think Floyd has more than 200K miles.

So if you have more than 200K miles, consider replacing both of these fans as they have worked a long time and can blow up any time. I know these fans cost some money, but they are still much cheaper than a head gasket job.

 

jpn6438 it could be related to a bad motor winding in the condenser fan as it is the one that keeps crapping out on you. I would say that you should consider trying to replace or at least swap out the fans with a known good working one and see if that resolves your issues.

 

Re date of mfg...
If you look at the photo I posted above, the factory relay has this marking:
1917A12 O, I think the relay was mfg'd on ? 191 days of 2007.

I am just guessing here because when I bought brand-new relays recently, the fourth digit was a 3, which is 2013.

 

It looks like I might have had a compressor problem all along and didn't figure it out until I got some gauges and looked at the service charts.

Although the low-side/suction pressure is fine, the high-side/discharge pressure seems capped at 200 psi. It hasn't gone higher despite the ambient temp now being above 80F and adding refrigerant to bring the low side pressure near the high end of the range. Discharge temp is also in or above the high end of the expected range. The diagnosis suggests a faulty internal compressor leak or discharge valve.

Once I read the service info, it became clear that the fans should have been turning on high without my mod. When temps are above 85F, the discharge pressure should always be above the 221 psi needed to trigger the high-speed condenser fans. In addition, I did get the software update to fix the PCM issue with the high-speed fans.

 

you can use the brake switch to trigger hi speed rad fan. I used this trick before on my 2002 to cool down the radiator during traffic.

 

Oh...I like that...plain and simple...I like that a LOT.
I've got a '77 Olds Starfire with a built up Buick 231 in it with twin electric fans.
On really good and hot days, sometimes the switch kicks in a hair bit too late and by the time the fans do start running, it's a loosing battle between the radiator and the water temp.
I'm gonna wire this up immediately, if not sooner.

 

I finally had to replace the compressor. The clutch wasn't engaging and measured an open circuit. One local shop wouldn't do just the clutch, and another claimed the clutch circuit was an open going through the compressor. After the repair, the high-speed fans are turning on automatically without my mod.

One hitch is keeping me from wrapping this story up with a nice bow. I measured the high- and low-side pressures after the repair, and the high side was just barely above 200 psi despite the ambient temperature at 98F and the high-speed fans on. It turns out my gauge dial was bent and getting caught on a screw right around 200 psi. After I fixed that, the pressure went up to 300 psi and tracks inlet air temperature. So now I'm wondering if my pressure from before was capped around 200 psi due to the compressor or the bent gauge. On one hand the high-speed fans never came on automatically, which says the pressure wasn't getting to 221 psi. I also believe the PCM code update was applied back in ~2008. Today I also got the VSA and fuel pump recalls done, but I don't think they included a PCM update (in the event the old update wasn't applied).

 

There is a bulletin with a PCM reprogram that addresses this problem.

Basically it still runs the fans on low speed until the high side pressure hits a certain pressure and then it switches the fans to high speed.