Can a relay drain power?

Jon

Jon

New member
I replaced my fog light relay with a generic relay that I had laying around. Matching plug pattern and it works.

Reason for replacing: the fog lights got stuck ON because of the relay being stuck in the closed position. I could tap on the driver front fender where the relay is and get it to cut off. I was going to order the right relay to replace it but found one in my scrounge box that matched the pattern and worked.

Oddly enough, around the same time frame my battery decides to drain itself to near dead after a few days.

Tossed the old Mexico made Optima yellow top out for a Duralast Gold.

Not a battery review, but this battery has done so much better than the Optima. It will do the "nothing click" a few times then the fast click, then start to turn the starter real slow. This lil 3.4 lights right up after that. Never got past the single click stage with the Optima.

So.... I have been judging the power draw by the spark when reconnecting the neg terminal. I had a noticeable pop which didn't seem normal to me. So I disconnected all of the wires that I had running to the pos side. Still the same POP. Removed all the fuses one-by-one from the box under the hood. Still the same POP.

Started my trouble shooting again today and first thing I notice is the Fog light relay which I replaced is clicking when I reconnect the bat. So I disconnected it and the battery terminal reconnect spark is minimal/normal.

I have an LED light bar spliced into the factory fog light wiring. But I never noticed a draw till after the new relay was replaced.

I measure 8.08V at the battery tonight. I'll post the new voltage tomorrow.
 
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ANYTHING electrical can cause a battery drain.

Clean your ground connections and your battery terminals
 
Voltage has to go somewhere. If the relay were causing your drain, it'd be because it's shorted to ground internally. I've never hacked open a relay but I suppose that's possible. If it is, it should be measurable on the bench.
 
The point of a relay is to keep whatever device it's hooked up to from draining the battery. FWIW, I had my 30" led bar wired up to my stock fog circuit for a while with no problems. I've since put it on it's own circuit with relay because I added a couple led pods to the stock fog light circuit. They have always worked without any problems. It's normal for relays to click. That's an indication they it's at least turning on. However, it doesn't mean that it's working properly. My suggestion is you might have a short somewhere.
 
I encountered the same problem. I had the factory Hella fog lamp setup and the relay went bad two years ago. I went down to the local stereo shop and they had, what appeared to be, the same one with a different name on the relay. Same size, same pinout locations, same number......I installed it and parked in the garage. 3 days later I went to start and the only thing that happened was the dash lights came on. I recharged the battery and everything appeard fine. Drove it for the rest of the day and parked it. 3 days later same thing happened. I opened the hood and started touching fuse holders and relays and then BAM....the new relay was hot...mhhh, so I pulled out the relay, charged up the battery for an entire day and waited for 3 days. This time it started up fine and as if nothing was wrong. I took my rig back to the shop and low and behold the relay's internal connections were different and was causing a serious parasitic drain. I rewired 2 of the external connections and then everything was back to normal.
 
ARKRWLR said:
The point of a relay is to keep whatever device it's hooked up to from draining the battery.
Click to expand...

HUH???

The point of a relay is to take a small amount of current and produce a large amount of current. A relay is a switch.

You can take the plastic cover off any relay and inspect it. Generally you will find burnt spots on the circuit board.


OP, the pop of spark you see when putting on the neg cable is basically a short somewhere. That can cause the drain. Get a DMM and measure the amperage (correctly) at the battery with everything off.
 
If the fog lights are off, the relay should not click when the negative is reconnected. That is a sure sign of a parasitic drain. I have never seen a Bosch-type relay with miswired internals, but that would do it. I DID have a Hella harness that was incorrectly assembled, so that the coil was permanently energized and the entire fog light load voltage was going through the switch. This just takes swapping two leads (85 and 30). The same thing could happen internally. The worst is, this error causes the lights to appear to be working normally. That was a bear to figure out what was draining the battery. The click gave it away, but it still took a while as I never expected an effed up harness plug.

Definitely time to try swapping in a different relay. (You must be able to borrow one from somewhere.) Then verify your car-side wiring:

foglite.jpg


If you DO NOT have DRL, and are tapping off the low headlight wire, then 86 should go to 12V+ and the switch tapped off the low beam wire, or vice-versa. Non-DRL 3G's have switched grounds on the headlights. This causes much miswiring.
 
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And that's how you trouble shoot! Boom! I'm 100% sure it's that relay since you guys have backed up my theory. Battery voltage was at 8.05V today. That's a drop of only 0.03V with the relay disconnected.

Anyone know the part# for the original relay?

I'd run new stand alone wiring for it but I already have so much hooked to the battery. I need an extra fuse block or something!
 
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[MENTION=56529]Jon[/MENTION], a relay cannot drain current. If the relay was switching on and off properly, that means, it’s not the relay that’s draining the current out of the battery. Even if the connectors on the relay look the same, they might be different from the inside and you might’ve clipped a ground or power connection on a wrong pin which although didn’t short the battery but provided it with a path with a lesser resistance which drained the battery. Please have a second look at it, I hope we can jump to a logical conclusion after that.

circuit board assembly
 
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No idea what relay harnesses that crap was so I just wired it to bypass that relay and now the problem is gone. And I can have just the light bar on if I want.
 
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