ARB compressor relay getting too hot
Submitted: Thursday, Jul 07, 2011 at 15:34
ThreadID:
87429
Views:
4543
Replies:
6
FollowUps:
3
This Thread has been Archived
jdbb
We’ve got an ARB CKMA12 compressor fitted in our 2006 Landcruiser and from the time we bought it in 2007 it hasn’t been the best. Whenever we use it to inflate the tyres it will stop after a bit of constant use – it will stop before four tyres are topped up from 28lb to 38lb pressure.
At first ARB thought it was a dodgy solenoid and we replaced that a couple of times. Then we were told it might be due to low voltage so we only use it now with the engine running. Last weekend I used it to inflate two of our caravan tyres and it stopped half way through the second one.
After it stopped I accidently touched the 40A relay that came with the compressor and it was red hot. You couldn’t hold it for more than a second. The wires coming to the relay were pretty warm as
well.
The compressor is mounted in the back of the Cruiser and is fed directly from the batteries with a 6B&S cable. The only other wire in the system is the stuff that came with the compressor and that goes through a 40A maxi fuse.
So now I’m thinking that maybe the relay or the supplied wiring is stopping the compressor.
Has anyone else had this problem?
Regards
John
Reply By: Robin Miller - Thursday, Jul 07, 2011 at 16:02
Thursday, Jul 07, 2011 at 16:02
A common problem is bad connection causing heat
John - same as the first thing to do if your battery doesn't turn the starter is to feel the battery terminal posts.
If hot bad connection caused by high resistance.
Clean can help , but it may be internal contact in your relay.
Try new relay , or if you don't mind playing with wires a bit , bypass the connection to
test.
AnswerID:
459367
Reply By: Lex M (Brisbane) - Thursday, Jul 07, 2011 at 16:32
Thursday, Jul 07, 2011 at 16:32
Have you got a multimeter.
Run the compressor under load and measure the voltage at various spots.
At the battery.
At the relay, in and out.
At the compressor.
You should be able to see a voltage drop if something is getting hot.
AnswerID:
459368
Follow Up By: Dennis Ellery - Thursday, Jul 07, 2011 at 19:16
Thursday, Jul 07, 2011 at 19:16
Good advice Lex,
Sounds like undervoltage if the overload keeps cutting out.
I blew a compressor up once, by running it on a cable with too much volt drop.
Luckily, Malz, the supplier gave me a new one – due to its internal circuit breaker not protecting it.
FollowupID:
732945
Follow Up By: Lex M (Brisbane) - Thursday, Jul 07, 2011 at 19:26
Thursday, Jul 07, 2011 at 19:26
The other issue (getting a bit technical here) is if the voltage from the relay is taken from the compressor voltage source, then the voltage drop from the compressor current reduces the relay voltage, which causes the contact pressure to reduce, which increases the contact resistance, which causes the voltage to drop, which causes the motor to draw more current, which causes the voltage to drop, which reduces the relay voltage .......
You get the idea.
Which is why a relay powered from the circuit it's switching should be de rated.
FollowupID:
732948
Reply By: Fred G NSW - Thursday, Jul 07, 2011 at 17:35
Reply By: Member - Murray R (VIC) - Thursday, Jul 07, 2011 at 19:52
Thursday, Jul 07, 2011 at 19:52
John
As the others have said bad contacts in the relay will produce heat. The contacts in a 40 amp mini relay are quite small about 2mm in diameter, with a constant 30 amp load they will easily over heat and cause a bad contact. If you smash the old relay open you will probably find that the contacts and armature blade are all blue, if so the relay rating is to small. If this is so I would fit a 70 amp relay instead as they have much bigger contacts and can handle the higher currant load. You should be able to get one from Bursons in Narva brand.
Murray
AnswerID:
459386
Reply By: Wayne's 60 - Friday, Jul 08, 2011 at 02:29
Friday, Jul 08, 2011 at 02:29
Greetings
John,
In short ................... no, we do not have that type of problem with our ARB CKMA12 compressor.
It would appear, from the information in your post, that the purchased product does not meet the basic criteria under which it was sold.
With respect, I would suggest that you ask ARB for a replacement unit, for comparison with your current unit, so that this matter can be finalised.
Please let us know the final outcome.
Cheers,
Wayne & Sally.
AnswerID:
459403
Reply By: jdbb - Friday, Jul 08, 2011 at 15:38
Friday, Jul 08, 2011 at 15:38
Thanks for all the replies.
I'll do a voltage
check on the system and will probably pull the relay out tomorrow to see what it looks like.
Would it be okay to take out the small switch and the relay and just put a bigger rated switch in the feed straight to the compressor?
regards
John
AnswerID:
459430