Okay, Dave--Latching Relays

[Steve Wood]

so I order some 40 amp relays.  Description says for headlight dimming, horn, etc.  Review says good relay, what can you say, it's just a plain old relay and I am using on my Ducati...

Gets here and they say latching relay on the cardboard backing under the plastic.

Now, I thought a latching relay required a voltage signal to switch on and then it would stay on even if the voltage was turned off...but then the next voltage applied would cut it off...to me this would mean it would not be suitable for a horn or such (I was going to use it on a hot wire)

If forced to, I will go rig it and find out if it operates like a plain ol' relay, or not..but I figured you know all things electrical and I would not have to go try it

[daveismissing]

You are assuming they know the English meaning of the word '"latching".
I'd be surprised if it really was. Your  definition is correct.

Presume its isn't a clear case so you can see the works? Suppose a test is in order.

[Steve Wood]

Okay, another question!

I grabbed a Hella relay off the shelf and it says 12 volts 20/40 amps

I have been told that this means 12v@40 amps, or 24v@ 20 amps

But...I looked this part #  933332181 up on the Hella catalog and if I understand it correctly, it says that normally open, it is good for 40 amps, but if the use is normally closed which a fuel pump would be, then the rating is 20 amps...which is cutting it close on a Denso pump that pulls around 17 amps at 70 psi on 13.2 v from the tests I have seen.  So, altho this draw is short lived, I probably would be better served with a 30/60 amp unit IF my interpretation is correct.

This all started because after I drive 20 miles or so, my car starts cutting out momentarily and then runs again okay for a bit...sometime s frequently, sometimes not so much.  I thought maybe my 20 year old radio shack relay was acting up but that is the easiest thing to change before i start swapping stuff around  

Car goes lean for a second, but has plenty of gas if I step on it immediately after.

[daveismissing]

You are correct they typically have different rating on open vs closed contacts.
If they are honest. Hella's 20 is probably Chinois 30a.
Kirbunz claims his new headlight harness has 80A relays, well that is what it says on the housing. I can still buy them at dealextreme for 5 bucks.

[Steve Wood]

Hellas relays are built in china in their super factory according to their literature..

The so called latching relays are also china but rated 30/40

They have to be regular relays according to the diagram on them....

First I have to figure out if that was the root of my problem and then I can worry about what ultimately ends up in the car....

[Steve Wood]

Looks like I barely got home before it seriously failed...so I guess I can now figure out why