headlight relay question

Hey guys another electrical question. I found some relays with a built in diode. The thing is they are 40 amp 1.8 watt consumption. Is it okay to use a 40A relay for the headlights on a 81 xj 550. It supposedly opens at 40 amps. I'm having a hard time wrapping my brain around this lol. thanks.

 

Your headlight takes 6 amps, so the relay is way big enough.

 

Will you be plugging it in to the factory harness, or making a new harness for the headlight feed?

 

Cool! thanks, I wasn't sure how that worked.

 

Hey k-moe I would have to make a adaptor or change the connector to fit old harness.
The reason I asked is because I took the oem relay apart and I noticed a diode. I think it goes with the blue/black wire that goes to the switch

 

I'm not entirely sure. The original relays are all proprietary. To my knowledge there are no plug-and-play modern equivalents available. I do recall a thread several years ago where the author stated all that was needed is to swap the terminals in the connector around, but I've never looked into that any further.

 

Okay thanks, If all else fails I might buy one and see if it works. If it does I'll give you guys a heads up.
On the oem is it the blue/black wire that goes to the switch that has the diode? if you happen to remember lol

 

I have not done a lot of research on this but suspect the diode is wired across the coil, which is used to dampen the spike from the coil when the relay is de-energized.

The diode in the XJ bikes is there to latch the relay closed once it is energized by the AC Generator. I suspect the reasoning behind the addition of the latching diode is you don't want the head light inadvertently shutting off driving down a dark road if a failure occurred within the charging system.

 

Yes sir, I think that makes perfect sense. I currently have a Panasonic nr20-n-5 . It works fine until you rev the engine and then it turns off the lights

 

I found some cheap diodes. I was thinking of using one externally. I was wondering if the amp rating is to small for this application though?
They are rectifier diodes 1n004 1A?

 

I don't think that is a valid number for the diode - maybe 1N4004? If so, that would not be the best choice, the current rating is OK but the peak reverse voltage might be too low (when the relay coil field collapses). The 1N4007 would be a better choice rated at 1 amp 1000V peak reverse voltage.

 

Thank you sir, yes I left out a 4. Thanks again I appreciate it. I'll try and find some 1N4007 .

 

Why? If you're using the diode to latch the relay as per (very good) drawing by rooster, it isn't a back emf diode. Just a latching diode. I don't see you need a high voltage diode for that.

 

The back of my mind says:
When the relay field coil collapses the voltage spikes. Too low of a voltage rating, and the diode burns out.

Keep in mind that I haven't done much with relays since I stopped working machine maintenance 15 years ago, so I might be wrong.

 

Well, it is kind of hooked up as a back emf diode or more commonly referred to as a freewheeling diode. Yes, it is true that the recommended diode is highly overrated, but better safe than sorry as the consequences of that diode being damaged and possibly shorting would result in damage to the diode block and possibly some wiring as that became part of the source to power the head light.

Could you check that number again (nr20-n-5) as it doesn't seem to exist. If it is the correct relay and wired properly revving the motor should not cause it to drop out.

 

Yes my mistake again. It is a mr20-n-5 I believe . on the relay itself has CA1a-12v-n-5 also ACA12135 and40130 NAIS. this is from the best I can see it. I had a new turn signal that was grounding and the relay would only buzz and not light up at all. After I found the turn signal issue it would work but cut out on higher revs. It is starting to run rough between 2000 and 3000 rpm's and I thought that could be caused by a dirty fuel filter. I my have other electrical issues. Thanks

 

Have you inspected the alternator brushes and copper rings?

 

I was messing with the oem relay and man was it corroded. I found three contacts I could clean on it and I actually got it to work.
As far as the little Panasonic relay I have no idea.

 

I did but I should probably look them over again. Last summer was the last time I checked em

 

If you want to be sure the replacement relay won't cause any issues...........from chacal at xj4ever.com parts catalog....

HCP429 OEM main HEADLIGHT RELAY. For all XJ550, XJ650 (except Turbo), and XJ750 Seca models. Small metal "cube" type relay has 3H5 inked on the top face and has a yellow-painted locking tab for identification.
$ discontinued, but please inquire about the availability of used original relays.

HCP16240 Aftermarket main HEADLIGHT RELAY. For all XJ550, XJ650 (except Turbo), and XJ750 Seca models. Small plastic "cube" type relay fits properly and functions like the original, but it will not "latch" like the original....meaning, if the engine dies, the headlight goes off. If that feature is not important to you (and many people do not even realize that the original relay has such a feature!), then this lower-cost substitute is for you.
$ 29.95

Harness connector wire colors:
- on all XJ550 all models, XJ650 all models (except Turbo):
* Blue wire with black tracer stripe
* solid White wire
* Red wire with yellow tracer stripe
* solid Black wire

 

Well, it looks like the Panasonic relay should work as long as the charging system is in good working order. If the charging system is intermittent in any way and without the latching diode the head light will go off whenever the AC generator output drops out.

With this one working with the latching diode and the Panasonic not working the charging system is likely a bit intermittent. A good place to start would be to just check the voltage across the battery to evaluate the charging system. You should see 14.5 +/-.3Volts at 2K rpm and up with a fully charged battery. K-moes suggestion to check the brushes and rings is good advice if you find the charging system is performing poorly.

 

I checked the brushes and rings and they looked pretty dirty especially the outside ring. I cleaned it and it helped so I cleaned it a second time and seem to help. The bike is running better between 2k-3k RPM's now. Now I'm getting around 14 volts on the tester at 4 thousand RPM's. Strange the tester shows around 12 volts after charging the battery but my charger gets up to the 80% light and then goes red. I'll clean the brushes again with some fine sandpaper and see if it helps with the charging.

 

I'm not saying a back emf diode doesn't need to be capable of withstanding the likely voltage spike from the collapsing coil feed. Clearly it does.
However the drawing patently does not show a diode across the coil, so its a latching diode. No back emf anywhere near it. Hence any 1n series will be fine, why are you making everything hard - seems to be a common thread here.

 

Here's the drawing:

 

Please refrain from making personal attacks.

 

Thanks for the help everyone. I paid a whole 1.39 for five 0f the 1N4004 lol. could I use them for the turn signal light in a gauge cluster?

 

Yes, if you are referring to the fix for the single indicator bulb when converting to LED bulbs in the flashers.

 

Yes sir, that's what I was thinking of. I did it to the 550 already. I have a little cm 250 I might fix up and it would need to do it to it as well. good to know the diodes will work

 

Well the bike is running better. still just a little rough around 2k RPM's. I think the battery is starting to be on the way out so I wedged another battery I had laying around in and it's doing better.
Charging a little better for sure. Wish I could find a good gel battery that would fit the 550's.
So the battery has to be 100% or it will run rough.
The grimiest relays can most likely be cleaned.
I'll try and update when I learn more about the Panasonic relays

 

Have you talked with Chacal?

 

I haven't yet.

 

When I had the relay opened up for cleaning I thought it would be possible to run a external diode. Maybe on the blue/black wire with the arrow (cant remember what that end is called, cathode?) toward the dimmer switch. I was thinking this way I could use a non diode relay to accomplish the same thing the OEM relay does
Now looking at this schematic I'm not sure. What do you guys think

 

Yes the diode can be installed externally and work, just be sure you get the polarity correct to prevent damage elsewhere. Connect the diode from the L/B wire to the W wire with the cathode on the W wire. The cathode of the diode will be marked with a white stripe.

 

Cool thanks!

 

Well okay then! the Panasonic Nais 40 with built in diode works but the connector is different so I made a adapter.
The Nais 20 works with a external diode, so I made a adapter for that. With your help my experiment was successful.
I enjoy working on this stuff so I have the crimpers and dies that are needed to get it done. Cool thing is about these relay's is that they are less than 10 bucks each.
I would post some pics but windows 10 wont let me view my photos. Getting a error message that I haven't been able to fix

 

You can't view them at all, or you can't view them when trying to post them?

 

I'm getting a file system error code (-2147219196) I can't view them at all
When I click on photos the screen turns black and then goes back to the desktop
When I go to files and then pictures I can see the thumbnails but if I click on one I get the error message ,it blacks out momentarily and the goes to the desktop