Honda Odyssey Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
64 Posts
Discussion Starter · #1 ·
I need someone to check their Fan Control Relay, preferably in a 2007 Odyssey EX-L. It is located in the passenger side of the engine compartment, in front of the under-hood fuse/relay box, under the brake fluid reservoir, in a grey box. The relay in question is a grey Mitsuba RC-5102 and will be on the left side of the box if there's a second relay (for the fog lights on a Touring model). If you take out the relay and are looking down on the contacts from the bottom of the relay, there are three smaller contacts across the top close together in a row. The outer two are silver-colored and the middle one is copper-colored (left-to-right pins 3,4,5). There are two more larger, copper-colored contacts in the middle under pin 4 (top to bottom 2, 1).

Applying 12V to pin 5 and grounding pin 3 should activate the relay, as illustrated in the service manual. When active pin 1 should connect to pin 2. Otherwise, pin 1 should connect to pin 4.

My relay seems to have the internal protection diode across the coil reversed, i.e. the diode was pointing from pin 5 to pin 3 and shorting out the coil. I verified this by measuring the polarity needed to energize the coil and then opening up the relay to see the diode inside. I haven't been able to find a schematic online.

The symptom which pointed me towards this relay was poor A/C cooling in the summer. It seemed like the radiator and condenser fans weren't coming on high. I'd only get decent cooling if on the highway at speed, and the refrigerant was charged OK. If this relay was indeed not functioning, I would have only gotten one high-speed fan (radiator only), two low-speed fans (A/C only), or one high-speed fan (A/C + radiator) but not two high-speed fans. I was going to try modifying the fan wiring to force high speed fans until I discovered the problematic relay.

I can upload some pictures if necessary.

Thanks,
Adam
 

·
Super Moderator
Joined
·
1,250 Posts
atoner:

I highly doubt you have a bad fan control relay. It sounds like you just need the PCM software update, per TSB 07-051. Have the dealer update the PCM with the latest software, as of the date of your visit. It will fix this issue and prevent other issues, as outlined in other TSBs.

TSB 07-051 A/C Cooling Is Poor; Condenser and Radiator Fans
Do Not Switch to High Speed
Applies To: 2007 Odyssey – From VIN 5FNRL3...7B000001 thru 5FNRL3...7B111734
2007 Odyssey – From VIN 5FNRL3...7B400001 thru 5FNRL3...7B456153
http://www.urvi.net/forumfiles/SB/A07-051.PDF

Here is the 2007 Odyssey Technical Service Bulletins (TSB) thread:

http://www.odyclub.com/forums/showthread.php?s=&threadid=46072
 

·
Registered
Joined
·
64 Posts
Discussion Starter · #3 ·
Thanks for the reply...but I measured the relay and the diode was backwards from the schematic. Also I had the PCM update done a few months ago along with the brake recall and transmission shudder fix.
 

·
Super Moderator
Joined
·
1,250 Posts
atoner said:
Thanks for the reply...but I measured the relay and the diode was backwards from the schematic. Also I had the PCM update done a few months ago along with the brake recall and transmission shudder fix.
So, were you able to test the relay, per the service manual, to ensure it is operating properly?

From the service manual:
Check for continuity between the terminals.

- There should be continuity between the No. 1 and No. 2 terminals when battery positive terminal is connected to the No. 5 terminal, and battery negative terminal is connected to the No. 3 terminal.

- There should be continuity between the No. 1 and No. 4 terminals when power is disconnected.

The service manual has a schematic of the relay, which is a five-terminal type. The cathode of the diode is connected to the No. 5 terminal and the anode is connected to the No. 3 terminal.
 

·
Registered
Joined
·
64 Posts
Discussion Starter · #5 ·
When I first posted, I had checked the relay against the Fans schematic but not with the relay troubleshooting directions since the Helm web site was so slow that night.

After finally accessing those documents, it is clear that the diode was backwards in the relay.

Before breaking into the relay, it needed positive on pin 3 and negative on pin 5 to energize. I have since cut out the diode and reversed it.

I got into checking the relay when I tried bypassing the E14/A5/FANH and E10/A4/FANL lines to ground to force both fans into high speed. This caused the radiator fan to come on high but the condenser fan to shut off, suggesting that the Fan Control relay wasn't working properly. After checking the ground (pin 2) I then checked the relay.

I will probably try replacing the relay and a few other ways to force high speed fans. It would be nice to know that I just had a backwards diode and that it isn't a more widespread problem. It is not unheard of to get components backwards in automated assembly. I see it every few months at work.
 

·
Super Moderator
Joined
·
1,250 Posts
1 - 6 of 6 Posts
Top