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post #1 of (permalink) Old 07-15-2009, 05:47 AM Thread Starter
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Thumbs up Why is this ABS Relay overheating in my CJ?

I have a 94 4.0L transplated into a 85 CJ. The OEM 94 harness has been mated to the 85 CJ bulkhead connector. The swap has went well, engine runs great with the exception of ABS relay we used to power the AC fan motor in the cab, a simple AM/FM radio, and XM SkyFi2 radio. Addtionally the output of the relay is daisy chained to other relays, one being the AC and the other a spare relay not being used. Could this be part of our problem?

When the ABS pump motor relay is installed in the PDC (this is what Jeep calls the power distribution center, it has all the fuses and relays), regardless if it connect to load, the temp of the case increases when energized. Even removing the relay from the PDC, energized on the bench, the case temperature will go over a 100 degrees in a matter of a 1-2 minutes. When checking another relay we could not get it to go over 90 degrees. Does this mean the relay is bad or is something else going on? I would really like to use compoents that already exist.

OR do we need to ID another ignition hot wire off the 85 OEM bulkhead connector and find a relay rated say at 40 amps with 100% duty cycle? IF so what location on the bulkhead and particular compoents should I aquire?

What do you guys think?

1985 CJ with a transplanted 94YJ 4.0L motor, T176 tranny, mainly stock otherwise. ><>
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post #2 of (permalink) Old 07-15-2009, 05:55 AM
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I suspect that the ABS relay is not a designed for 100% duty cycle. Try a generic headlight relay. They'll handle 40 to 50 amps continuous, and they're cheap.

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post #3 of (permalink) Old 07-15-2009, 02:58 PM
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Quote:
Originally Posted by DuaneD View Post
I have a 94 4.0L transplated into a 85 CJ. The OEM 94 harness has been mated to the 85 CJ bulkhead connector. The swap has went well, engine runs great with the exception of ABS relay we used to power the AC fan motor in the cab, a simple AM/FM radio, and XM SkyFi2 radio. Addtionally the output of the relay is daisy chained to other relays, one being the AC and the other a spare relay not being used. Could this be part of our problem?

When the ABS pump motor relay is installed in the PDC (this is what Jeep calls the power distribution center, it has all the fuses and relays), regardless if it connect to load, the temp of the case increases when energized. Even removing the relay from the PDC, energized on the bench, the case temperature will go over a 100 degrees in a matter of a 1-2 minutes. When checking another relay we could not get it to go over 90 degrees. Does this mean the relay is bad or is something else going on? I would really like to use compoents that already exist.

OR do we need to ID another ignition hot wire off the 85 OEM bulkhead connector and find a relay rated say at 40 amps with 100% duty cycle? IF so what location on the bulkhead and particular compoents should I aquire?

What do you guys think?
This sounds very much like one of two problmes...

1. You have too much load on that relay if it's getting to well above 90 or 100 degrees,
OR,
One of your components connected to that relay is shorted out.

2. You might have an internally protected relay (Thermal Protection)...
They DO make a lot of heat, but shouldn't kick out under reasonable load.
----------------------------------

Personally, I'd find out how much amperage that relay is handling.
Common automotive relays are designed for 20 to 30 amps.
Anything over that, and you are just ASKING for trouble.

This is something I made up for guys having problems with figureing out relays...
(it will probably show up on dale's site now )
http://www.civilianjeep.info/Wiring/relay02.gif
-----------------------------------------

And these are the relays I prefer for Jeeps.
They grow wild on GM vehicles, especially Cadillacs in the salvage yards, and they are SEALED...



And you can use a common 'Cheapie' relay to get you in if you have problems on the road...


----------------------------------------

If you want to go with a HIGH POWERED relay, then consider a 70 amp version like is used for starter relays on motorcycles, ect.
I power up my second battery, use one to control my electric fans, electric air compressors, ect. since the common 30 amp variety is right on the verge of destruction while handling alternator current or electric fan currents...
(Show next to an air compressor pressure switch)



Look at the size of the blades on that relay!
This thing will handle around 70 amps continuously, and it's easy to find since Harley Davidson has used it as a starter relay for over 20 years.

So Many Cats, So Few Recipes...
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post #4 of (permalink) Old 07-19-2009, 10:25 PM Thread Starter
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Thank you for both for pointing me in this direction. I wish I had access to amp clamp meter to look at draw for each item. None the less, your suggestions and exmaples really made a difference. I ended up using Headlight Relay part number AR419 relay from NAPA for about 18 bucks. I just don't have any junk yards close to me. Have a Good week.

1985 CJ with a transplanted 94YJ 4.0L motor, T176 tranny, mainly stock otherwise. ><>
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post #5 of (permalink) Old 07-20-2009, 10:05 PM
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Quote:
Originally Posted by DuaneD View Post
I wish I had access to amp clamp meter to look at draw for each item.
Those donít work on DC.

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Those who understand binary and those who don't.
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post #6 of (permalink) Old 07-21-2009, 05:52 AM
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Quote:
Those don’t work on DC.
Yeah, they do, if they're designed to. I have one, and it's surprisingly sensitive, reading to tenths of an amp, although I don't recall how accurate it is down there.

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post #7 of (permalink) Old 02-17-2010, 07:54 PM
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Well good thing you already found an answer to your query. yes usually, a poor ground or error in electrical connection causes relay to overheat.
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post #8 of (permalink) Old 02-18-2010, 12:43 AM Thread Starter
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I agree, a good or multiple ground(s) is so important. More than I first realized.

Quote:
Originally Posted by ema View Post
Well good thing you already found an answer to your query. yes usually, a poor ground or error in electrical connection causes relay to overheat.

1985 CJ with a transplanted 94YJ 4.0L motor, T176 tranny, mainly stock otherwise. ><>
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