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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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#296 ·
I pulled the relay out altogether and started the car and AC but the 2 large condenser fans still spin. Is there any other way of determining if they are faulty aside from the compressor not engaging? I don't have a multimeter.

I've ordered a replacement one anyway seen as though they aren't too expensive.
 
#297 ·
Not really without a meter. Honestly the rate these seem to fail, its a good idea to replace it anyway. The original relay fitted is substandard and prone to premature failure, and Honda only stocks the updated part now. Condenser / radiator fans are controlled separately from the compressor relay, so if the condenser fan runs but not the compressor, it could be a reasonable indication that the compressor relay isn't pulling in or the clutch plate isn't engaging fully. You can either take it for diagnostics or wait for the relay, did your local dealer not have one on the shelf?
 
#299 ·
Air con relay switch

Chaps, my air con packed up after heavy rain . Though it needed re-gassing. Took it to f1 auto centres who we're going to charge £29. After 30 mins they said it was most probably an electrical fault. Got the relay from Cox the day after ordering. Hey presto it now works.

Turns out a resistor had come away inside which was the rattle I could hear.
 
#301 ·
why don`t people remove the relay and short the two exposed contacts in the box to simulate the relay being energised ?

Just make sure its not the supply contacts.

Would that not prove the fault was in the relay before spending £20 and finding it doesn`t solve anything. :?:
 
#302 · (Edited)
Shorting the contacts means the compressor is running unprotected. If it's just for a couple of seconds to check operation then go ahead, if you know what you're doing, otherwise don't risk damaging the compressor in case there's a non-relay fault locking out its operation to protect the refrigerant system.

Most people ask questions about the AC because they don't understand the system - not a dig, nobody knows everything - and I'm not going to put half an idea in someone's head that leads to them believing they can just loop it out permanently and avoid paying £20 for a relay, or injuring themselves or damaging something else in the car because they can't identify the correct pins to loop out. I do point out that people should take the car to a specialist if they don't know what they're doing, and that these relays are substandard and should be replaced as a matter of course anyway.
 
#305 ·
For anyone interested in alternative modes of AC failure, I've got another one that cropped up today.

My dad asked if I would take a look at his car, a 5 year old Hyundai i30, as the AC had gone from ice cold to ineffective almost overnight. I reasoned being a sudden loss it could be an electrical issue, and got him to start and stop the Compressor with the engine running, to see if the compressor clutch could be observed starting and stopping. No luck since the compressor clutch is a solid lump on the i30 and doesn't have a visible gap to see the compressor turning like in the civic, however we did observe there was no change in engine note when starting and stopping, therefore probably suggesting the compressor was not performing as it should.

I asked him to turn down the AC to cold, up to full fan blast, and off recirc so it was getting warm air from outside, this should have meant the system was working hard to circulate refrigerant and there would be a noticeable heat difference between HP and LP lines (silver metal rigid pipes running between compressor, condenser and the cabin) but there was none.

I then checked over the system just in case, and could see between the radiator and condenser in front of it, the condenser had sustained damage which had deformed the tubing and pushed out the fins. Observed from the front, it was clear the condenser had been hit by a stone in its exposed location behind the flimsy plastic grille, and this was the source of the leak. Without refrigerant in the system, the compressor will not run as the LP switch doesn't sense a high enough pressure to interlock.

Although we initially suspected an electrical issue as the failure was sudden rather than gradual, we were proven wrong. A loss of gas does not only occur from the compressor drive shaft and can happen at any time unfortunately, being especially vulnerable where the condenser is located in front of the radiator. In his case, as the i30 is a quite spacious engine bay he should get away with only having to remove he radiator and a few ancillaries. The Civic engine bay is much more complex and tightly packed, which could be several hours labour on top of the replacement part and regas.

One final note. Whenever you sustain damage that means your system is open to the elements, as in this case, it is imperative that your garage replaces the drier core at the same time as replacing the defective component. Refrigerant oil is highly hygroscopic (absorbs water readily) and the filter drier removes this moisture if any enters the system, to prevent ice forming in the pipework or damage to the compressor. When open to the elements, the drier core quickly becomes saturated and will no longer be able to absorb system moisture, and will almost undoubtedly cause much more damage in the future. To save this hassle, ensure and insist that the garage will change the drier whenever you have to get a component replaced in the refrigerant circuit.

Good garages shouldn't need prompting!
 
#306 ·
So I replaced the relay and it worked!

Strange thing is that I heard the clicks as the AC is turned on and off with the old one in and I had it tested with multimeter by a friend who said it was ok.

So no real sign from what I could tell that it was faulty...but it clearly was faulty.

Won't be taking AC for granted, thanks for the assistance.
 
#307 ·
just a quick question to put my mind at rest -

I have checked my relay and voltages and when I press the ac button on I can see the clutch spinning and then going off when I turn off the ac. The temperature from the vents doesn`t feel any different with ac on/off - pollen filter is clean.

I am hoping it just needs a regas but could it still be the wrong gap on the clutch even though the clutch is spinning ?
 
#308 ·
If there's a slight but noticeable difference in engine note when the compressors is started / stopped, then the compressor (which is a heavy load and therefore makes the engine work harder) should be engaging properly, and all you'll need is a regas.
 
#310 ·
I have just got back from Honda, and the diagnosis is that we need "Clutch assy and Field coil Assy"

They quoted parts price at £524 plus the tax mans cut.

So as the clutch is not engaging, what options do I have?

Does removal and replacement of the clutch and the field coils mean I have to have it re-gassed again?

vette
 
#311 ·
Not necessarily, there were a few guys having trouble last year with their compressors not engaging, was traced to the clutch needing shimmed to bring it closer and help it engage, as it wasn't doing so in warm weather. Think it might have been about this time last year on this thread in fact.
 
#313 ·
Probably recirculating to being the air temp in the car down if its hot outside and you've got a low AC temp set, then switching into normal flow mode. Recirculate as you'll know brings down cabin temp faster as you're cooling the cabin air rather than fresh warm air from outside. If your cabin gets cold then your relay is fine.
 
#314 ·
Thanks to you guys for the info, had the usual problem of no cold air coming out with AC on, got it recharged but no change. Ordered the relay from Cox and just fitted it, all working perfectly now :) The old one rattled when I shook it too, not sure if that's a sign it was faulty but seems to tally up with everyone else.
 
#315 ·
AC/climate control failure

Hi there,

I found this post about AC in Civic but I can't find actually any information what is result of this failure. I bought 1 month ago Civic 2007 and I noticed two problems about a airflow and temperature. First of all I think that I can't really set temperature there because when AC is ON and I have set 22 degrees the air is still blowing so cold and even if I set max temp. there is still cold air coming into the car. Other thing is that after long travel around 2-3 hours power of blowing disappear or decrease. It happened twice that I couldn't get any airflow and although I had set max fan speed there was only little airflow. Please could someone advise what is wrong. Is this typical failure or something other?
Many thanks
 
#318 ·
Took my car in for a regas the other day as I wanted the system drained and cleaned too after the air con packed up. I was thinking it was the relay but wanted it cleaned anyway. So the garage (F1 Autocentre) do the re-gas but they show me the printout that shows it the air con system had just under double the amount of gas in it than it should have had! I'm hoping it hasn't blown the compressor.. Anyways, got to replace the relay now as its as rattly as a baby's rattle... Fingers crossed...
 
#320 ·
Just had a look at my A/C relay and it's rattling like a halfords spray paint. My parents asked me to take a look at their civic's A/C because theirs isn't working either and there was no relay plugged in. hmmm...
 
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