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updated air-con compressor relay to prevent failure

AC/Heater 
392K views 643 replies 222 participants last post by  culzean 
#1 · (Edited)
This is a common cause of failure of the A/C on our civics.

In fact just a week ago Honda issued a Bulletin about it. The original fit Omron relay is suseptable to moisture ingress. This can form nitric acid in the presence of the normal arcing as the contacts operate. This will lead to corrosion and eventual failure. The Bulletin warns that the relay can fail either open or short circuit. If the latter this forces the compressor on to 100% duty cycle and can burn it out.
The remedy is a replacement relay from a different manufacturer - Mitsuba - that is a better quality item. The bulletin warns that the EPC is not yet updated, so you have to order this countermeasure part number directly to recieve the new part, otherwise you will just get the "old" part. I'm surprised they are not doing a campain over this considering if can fail in a way that might lead to screwing up other parts of your aircon

This the bulletin number:-

SM-10-002-00

It affects ALL civics (and CR-V and jazz) upto and including 2011 model year

Here is the countermeasure part number:-

39794-SDA-A05

RELAY ASSY., POWER (MICRO ISO) (MITSUBA)



The datasheet for the original Omron part is here:






The specific part is G8HL-H71 which appears to be a Honda specific version not listed on Omron's website - the standard relay is 180ohm and the Honda version is 120ohm coil resistance.​


The Mitsuba part seems to already be used on other Hondas. I found this link for example​


 
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#245 ·
I've had problems with my A/C recently.. not blowing cold any more.. sometimes blowing cold for a minute or so, then not.

So i've been reading through this thread.

Tonight I checked a few things.. its cool outside, and for some reason the A/C is working at the moment.. strange.

But this is what I see at the moment.

I have the engine idling. I switch the A/C on. I hear a clunk, and a fan comes on in the engine bay. When i look, i can see that the clutch has engaged, then shortly after the engine revs drop, to the point where it sounds like its going to stall, but recovers. Then a short while after, and clunk again, and the clutch dis-engages, and stops spinning the 'pump"? compressor?
anyway, then again in engages, fan comes on, revs drop, and and cycles like this.

each time the clutch engages, or dis-engages, I hear 2 short clicks from where the relay is in the engine bay.

So I guess all of this is normal for a system that is working ?
- drop in revs.. maybe a duff battery ?
- 2 short clicks from relay each time, normal ?

So, the other day when it didn't work.. i did not lift the bonnet (but will next time) but I could hear the same clunk of the clutch, and the fan come on, but it was not blowing cold..

Any pointers, or next things to check ?

I am assuming that maybe the relay is okay ? or okay now, but sometimes not ? although I always get the clutch clunk.

Other than that, just a re-gas needed? but as of now its blowing cold..

Thanks!
 
#247 ·
Nope, no need to go for a relay this time, sounds like your compressor is clutching and declutching perfectly fine therefore the relay is operating correctly. I'd suggest you are short of refrigerant, if its short cycling then most likely the pump is starting and drawing down the LP side of the circuit until the LP cutout operates.

The refrigerant circuit works on expansion with the application of heat, kind of like water turning to steam but in a more linear and consistent way. When operating normally, the circuit allows a metered flow of cool liquid refrigerant into the evaporator (the cooling coil in the air conditioning system) which is warmed up as it absorbs heat from the air passing over the cooling coil. This warming of the liquid is sufficient to boil it into a gas, also raising its pressure due to the pressure / temperature relationship of the refrigerant. We want the liquid to turn into a gas as liquid return to the compressor can destroy the seals (you can't compress a liquid). When the refrigerant circuit shuts down, it does so by closing off a valve which was metering the refrigerant flow into the evaporator, and the pressure in the evaporator drops as a vacuum forms now the compressor isn't being fed with refrigerant. The LP side of the circuit is protected by the LP cutout switch, designed both to stop the circuit once the evaporator has been emptied down to a certain pressure, and to protect against pipework damage in the event of a loss of refrigerant which would have the same effect as that metering valve being closed off.

So long story short, you need a recharge of refrigerant. To keep the system healthy and not needing recharged regularly, try to run your AC system once a week at least, it allows the system seals to get lubricated which prevents them perishing - at which point refrigerant can escape.

Hope this clears up the dilemma, its a complex subject but the one I'm stuck with!
 
#248 ·
Thanks so much for that description.. while I don't quite understand it all, it sounds like the relay is fine, and I just need to pop to Honda for a re-gas then ?

So, when it clutches, de-clutches, its normal to hear 2 clicks from the area where the fuses/relays are ?

Is one click for the fan, and the other for the clutch maybe ?

Anyway, thanks very much!! Hopefully Honda won't spend too long to diagnose the 'fault' as that can normally cost more than the actual fix. :)
 
#252 ·
That's fine, its a dark art to master and I still occasionally get myself tripped up in the complexities of it. The base line is that if there isn't enough refrigerant, the compressor will cut in and out regularly as it tries to cool the cabin to the demanded temperature, but trips to protect itself from drawing too low a vacuum.

Unless in warranty I see no reason why you should have to take it to a main dealer. While specific maintenance work is suited to the manufacturers workshop knowledge, this is stuff that any garage with AC facilities could handle. I'd still steer clear of bargain bucket outfits who tend to have 'monkey-see, monkey-do' AC techs with at most a basic understanding of how to fault diagnose and usually end up overfilling systems in error, which can lead to serious compressor damage.

Your best bet is to find a proper car AC place, usually they're also specialists in car electrical work. They're much more experienced and are more likely to give you a sound diagnosis rather than just guessing at a faulty component, and their prices are normally quite competitive against main dealers prices - especially right now before the summer rush of work.

Just my suggestion, getting it done right first time is better than taking a chance with a poorly trained spanner monkey (in my experience!)
 
#254 · (Edited)
Have a look in the yellow pages, I think you could prob knock at least something off that and get it done by a proper professional. I know the bargain places normally advertise around £30 in summer which is surely too cheap to do any good.

That said if you think £65 is a fair price then fair enough, I usually get stuck in the trap of endlessly scrabbling to get another few quid off something before I realise what a pointless waste of effort it is when I can afford the extra few quid for less hassle!
 
#255 ·
Last week discovered the a/c was working unregular. First i was thinking maybe my new satnav disc with new firmware was causing this. But after search the forum found out it was an bad Omron relay. Today got new type from honda dealer for approx. €26 and now my a/c is working perfectly again. Thanks for shearing the info.
I opened the old Omron to find a lose resistor in there.

Verstuurd vanaf mijn SM-N9005 met Tapatalk
 
#256 ·
I've fitted the new relay and had my system regassed. Now the weather is warming I've turned the temperature dowm and get a lot of fan noise but the air is warmer than outside and remains that way. I've got it set to "auto" and it puts the climate into recirculate mode.

The compressor clutch is kicking in and out when I press the aircon on/off button and I'm getting water from the overflow underneath the car.

Any ideas/suggestions I can try as I'm hoping the warmer weather continues and I get to use the aircon more.
 
#257 ·
Water underneath your car i as far as i know condens water so it looks like your aircon is really cooling the air. I guess maybe something wrong with the air control valve that is regulating between hot and cold air. Maybe that why no cold air is comming out of the vents? Does the temp regulation works normal when aircon is off?

Verstuurd vanaf mijn SM-N9005 met Tapatalk
 
#258 ·
As far as I know it's working fine otherwise. If I set the temperature at 26 it would get warmer in the car than at 22

Sent from my GT-P3110 using Tapatalk
 
#259 ·
My air con stopped working so had a re-gas and still no joy! Garage said it would be the compressor and would be expensive! I found this thread replaced pollen filter and relay and it works fine now! For all of you who check the relay by listening for the click mine was clicking when the ac was turned on so it's worth changing it anyway! Thanks civinfo!
 
#260 ·
Had some weird aircon noises late last summer (only when ambient over 20C), replaced the relay with the new version, will wait and see if all is well but at half the price of my last AC service/re-gass and the potential of saving the compressor (More likely non AC at my cars age) its a easy and very simple choice :)
 
#264 ·
Someone has tried to take it out with pliers by the look! My old one did that when I took it out!
 
#265 ·
Yeah it's been attacked with pliers. How long have you had the civic, if its not been long take it back, show the garage and ask if they'll rectify it free of charge. Sounds cheeky but if they've sold it with a defect then you've got a chance.
 
#267 ·
Cost me just over £20!! Easy to fit as well! Old one is a little tough to get out though!
 
#268 · (Edited)
Damn, still not working!!!

I've checked the relay and it is the Omron type but is clicking and the compressor is engaging when the A/C is turned on so I've just had a gas re-charge and its still not working so I'm at a loss as to what the problem is

**update** just checked it again and when I switch the A/C on, I get the two fans and compressor running for about 5 seconds then they stop so I'm guessing it is the relay
 
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