[rjlane1]

Ah, ok, thanks for clarifying that. That'd explain why there isn't a lot of information on this Odyssey and the Radiator Fan Switch that a lot of other cars do have. I tested that sensor today and it is working properly. So, my observations so far would be that my Radiator fan is intermittently working. When the car is cold and I turn the AC on, both fans come on as expected. It seems to me that when it comes up to full temperature, the Radiator fan stops working. That is the part I can't explain. I'm working on a theory now of the radiator reservoir cap is cracked, perhaps causing there not to be a pressurized cooling system, thus preventing the coolant to come up to the proper temp to trigger the fan?. Any thoughts on that theory.

 

[John Clark]

The fans have a high and low setting. On low setting they run in series through the condenser fan (passenger side fan) fuse and relay only. On high speed they are powered individually by their own respective fuse and relay.

With AC off, the low speed fan is triggered at an ECT temp somewhere around 195-200F (I can't recall the exact number.) Both fans should run on low speed when that temp is reached. If you turn the AC on the fans will kick on to high speed at 221PSI on the high side of the AC system. High seed is also triggered at a high ECT temp at (I think around 205-210F.) Both low and high speed have their own outputs from the PCM. The PCM will turn on either low or high speed fans depending on what inputs it's getting. You need to determine whether you have an input problem (ECT issue) or an output problem. If you look at the wiring diagram it appears that ECT2 that the PCM uses to control fan speed. You need a scan tool that can look at ECT2.

 

[John Clark]

If you're low on coolant then, yes, that would affect the ECT temp and the fans would very likely not come on at high temps. Make sure your coolant is full.

 

[rjlane1]

The fans have a high and low setting. On low setting they run in series through the condenser fan (passenger side fan) fuse and relay only. On high speed they are powered individually by their own respective fuse and relay.

With AC off, the low speed fan is triggered at an ECT temp somewhere around 195-200F (I can't recall the exact number.) Both fans should run on low speed when that temp is reached. If you turn the AC on the fans will kick on to high speed at 221PSI on the high side of the AC system. High seed is also triggered at a high ECT temp at (I think around 205-210F.) Both low and high speed have their own outputs from the PCM. The PCM will turn on either low or high speed fans depending on what inputs it's getting. You need to determine whether you have an input problem (ECT issue) or an output problem. If you look at the wiring diagram it appears that ECT2 that the PCM uses to control fan speed. You need a scan tool that can look at ECT2.

Will Torque be able to look at something like that, or do I need to bite the bullet and have the mechanic put it on their computer?

 

[John Clark]

Not sure. Plug it in and see. I'm guessing it will show ECT1 but it may not show ECT2.

 

[-JnC-]

Thank you for the great in depth investigative work and prognoses of the issue. I have an 07 EX-L ( not sure if that makes a difference) and have installed the VCMuzzler, its been on the car for the past 2 years without an issue. I have been having the same issue with the AC as stated in your original post, its fine when the car is moving but completely useless in stop and go traffic. I checked the fuse and the fuse was good as well, both the fans turn on when I turn on the AC but seems like they run at low speed rather than high.


Is it the muzzler thats causing the fans not to kick into high?

 

[OdyMember]

Is it the muzzler thats causing the fans not to kick into high?

The VCM is NOT active when idling. It is possible that you may be low on refrigerant. Has it been serviced lately?

 

[John Clark]

No, the Muzzler has nothing to do with the AC or the radiator fans. As mentioned above, I'd have the system serviced.

 

[-JnC-]

My system was fully serviced a couple of years ago, new compressor was installed along with system recharge. I guess I should have it looked at again.

 

[John Clark]

To see the difference between low speed and high speed turn the AC off and let the vehicle idle when it's warmed up. The fans will cycle on and off of low speed. Then turn the AC on and the fans should go to high speed.

 

[pIOUs]

Big thread back from the dead. 07 EX-L 210K miles. System evac and recharge by weight. High side almost 300 with ambient temp about 100 degF. Low speed works on both. No high speed. System gets warmer during 94+degF days with idle and start/stop driving.
All the checks for ground or voltage came out fine at the fan control relay socket and between FCR and the radiator relay. Diode good (thanks for previous poster on locating it). I didn't ground those wires and do the PCM connector checks. Swapped in known good relay 4 prong. 10A and both 30A (30, 9,11) are good. The only weird reading I got was from the 5 prong control relay. Supplied battery voltage and heard the click, but prongs 1-2 should have solid continuity, but it's erratic instead. With the alarm on, the meter sort of chirped at me. I'm going to Autoparts store for a cheapo sub to swap in. New thoughts?

 

[John Clark]

You swapped in a 4 prong relay for the fan control relay? What good does that do? I suppose it would run the fan on high speed if everything else was working. When the FCR is activated it grounds the AC condenser fan and it will should run on high speed as long as the AC condenser fan relay is also activated and pulled closed. For the radiator fan motor to run on high speed, you need a good radiator fan relay and fuse #23 & 11 inside the car. I didn't see that you checked fuse #11 in the driver's under dash fuse/relay box.

 

[pIOUs]

I think it was #30 under the dash (10A). 23 checked just now with meter too. 11 (30A) is in under the hood right? Checked that. I swapped 4 prongs with new 4 prong I had saved for clutch issue way back. The 5 prong I just did a continuity test. I purchased new from autozone and it tested identical to the old one, so I'm thinking that is a dead end. I plan to pull the 4-prong connector to the pressure switch tomorrow and test the medium pressure circuit that is brn/wht and blk. Jumping pins 2-3 should put them on high with the key in pos 2.
If that switch is bad, I'm guessing I have to evac the system again to replace it. It will leave the system open to atmosphere when it comes out right?

 

[John Clark]

Here is the diagram for the 2007 Ody. My original pics no longer show due to issues with the forum.

http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=140877

As you can see, you need fuses 23 and 30 in the driver's side underdash fuse box and #11 and 9 in the underhood fuse box.

The fan control relay has continuity on pins 1 & 4 when not powered. When powered there should be continuity on pins 1 & 2. It's just a relay that has both a normally open and a normally closed contact rather than the 4-pin relay that just has a normally open and is powered closed.

You can check if the pressure switch is working by checking for a ground on pin 4 of the radiator fan relay when the AC is on and the PSI in the system is over 221 psi. The ground on pin 4 is the computer's signal to run the fans on high speed. If you have a ground on pin 4 with the AC on then everything prior to that is working. If you're missing a ground on pin 4 of the radiator fan relay when the AC is on and the system is over 221 psi then I'd suspect a problem with the pressure switch.

Also, to be clear, what happens to the fans when the AC system hits 221psi? Do they stay in low speed or do they actually shut off? If they stay in low speed then I suspect there is no high speed signal to pin 4 of the radiator fan relay from the PCM.

 

[pIOUs]

Thanks for the details in your response. I will check the switch as you say. Both fans run on low when the AC is on. The system is really high on the high side after the mechanic refilled by weight. He said it was within acceptable range, but alerted me that even with a reading at 300psi+ the fans were not switching to high. At normal op temp with no ac it will turn on both fans, but never at high since the temp of the coolant is pretty much on the low end with fresh coolant after a flush and new pump. I used a diagnostic feature in my scan tool that turns on both fans and they sounded almost loud enough to be in high mode, but I couldn't tell for sure since it didn't indicate what I was actually testing.
When you test pin 4 of the radiator fan relay, you mean pull it and test the socket for ground right? I just want to be sure.

 

[pIOUs]

Also I have continuity between pin 4 of the radiator fan relay and pin 3 of the fan control relay. If your saying that pin 4 isn't getting the signal from the PCM, then the PCM isn't getting input from the switch to tell it to do that. If I'm following your thinking. hmm. I'm checking the switch tomorrow for sure.

 

[John Clark]

Yes, pin 4 of the radiator fan relay and pin 3 of the fan control relay get their ground from the Fan High signal when the PCM commands high speed. That, in turn pulls the radiator fan relay and the fan control relay in and the fans will run on high speed.

If you have an enhanced data and bidirectional scan tool that will turn on the fans, that's great. If, when you toggle them on with the scan tool, they're turning on faster than the low speed you see right now then that means everything in the radiator fan, condenser fan, and associated relay circuits are working fine and you have an input problem, most likely the pressure switch.

In the same wiring diagram I posted above, on page 2, you'll see the pressure switch or input side. Take a look at the A/C Pressure Switch pins 2 & 3. Those two pins should close when the pressure gets above 221psi. Based on the scan tool's ability to bidirectionally turn on the fans to high, that pressure switch would be my next check.

Once you get the fans running on high your pressures should come down from 300psi and the high speed fans will cycle on and off based on pressure (the 221psi.)

 

[pIOUs]

Thanks again. My scan tool has a fan option under PGM-FI for radiator fan. With the engine off and the AC unit switched on, both fan run on low. Switching the AC off and using the radiator fan option in the scan tool turns them both on high. That verifies to me that all the electrical in Fans, relays, and fuses and that circuit is fine. I did unplug the pressure switch and shorted 2-3 and got low speed to come on, then shorted 2-3 also and it remained constant when the ac was switched on. At this point I'm pretty sure the switch is toast. While doing these checkes I noticed my high-side service port bubbling (Ugh) so I goose the valve for an instant and noticed it stopped. I guess there is one tricky part of putting gauges on this van; if you don't clear the valve with a quick vent, it will not fully close. I'm hoping I won't need that too.

 

[John Clark]

A better test of the pressure switch would be to leave it plugged in, start the engine and turn on the AC and use a jumper wire backprobed into pins 2 & 3 to simulate high pressure in the system. Your fans should turn on high speed. If you do it unplugged then the PCM thinks the pressure is below 28 psi which causes an implausible situation as it can't be both low and high at the same time.

 

[pIOUs]

OK good idea. I did get low speed with it unplugged, but I thought I could also simulate high pressure in the system by jumpering 1 and 4. That didn't work. On page 21-61 is says you should get high-speed by jumpering 2-3 (step 7). I didn't have the right backprobes to reach in the plug from behind while plugged in so I moved forward on replacing the switch. The mechanic replaced it and we still have no high speed. All I can gather is that the signal is not reaching the PCM due to a bad connection or broken wire. With the system charged and ambient temps (mid-90s), the system is 250+ psi on the high side and should be sending the signal over the BRN/WHT pin 3 so the PCM can send the FAN-HI signal to the circuit. If the is the only variable that needs to be satisfied then the BRN/WHT wire is broken. If that is NOT the only requirement, then the problem is elsewhere. When I went through the the troubleshooting for the A/C pressure switch, I had to go into the cab and test a few items on the climate control system. One of them was the evaporator temp probe. I'm not sure why I got OL on the 22pin connector (A/C Control Panel) between 3 and 14 when I'm supposed to get like 9K ohm. I checked the temp sensor directly from its 2-pin connector and got that reading so that was weird.
So I'm still stuck on low speed with a new pressure switch and a few diagnostic checks left to make before a dead end. Again when I command the Radiator fan on from diagnostic tool they both come on high, so outputs and the circuit check out for me. I've left it to the mechanic to troubleshoot now, and reviewed the system and the checks I made with him. I would much rather solve the mystery (with a modest investment) than eventually come up with a cheat that leaves the system on high all the time, but my time is running short ugh.