jbtvt

Cheap fixes for your circuit opening relay - overview, new capacitor install, refurbing contacts, swapping in a higher uF capacitor to prevent AFM signal loss, etc. Hate reading threads about people spending $$$ for new ones...

http://www.youtube.com/watch?v=V8l9QvLAajA

MudHippy

Interesting. I like it.

I "refurbished" the contacts on mine already. Well, as best I could anyway. I didn't use solder though(would that really even work effectively?). I just smoothed them out as much as I could with a file, without removing too much material. Hadn't thought about replacing the capacitor(or why I might want to). It looked fine as far as I could see(no corrosion/leakage).

You can buy a new COR for ~$40. Not OEM of course, but it's just a relay...does it really matter? I highly doubt Desno is so far advanced in their relay manufacturing technology that it actually does(unless you know something I don't).

Micro sign: µ (Alt+0181)

jbtvt

Thanks. For future reference, where were you able to find one for $40? I just remember coming down with a severe case of sticker shock when looking for one a couple years ago.

Those Denso contacts seem pretty indestructible, and a little sandpaper usually does the trick, but solder can help in some cases if the contacts are badly pitted, it's easier to smooth out. Electrolytic caps are a wear item, good ones usually last decades at average temp use, but at high temps and especially if they get wet or have polarity reversed they can fail, sometimes without showing signs. But yeah, if it wasn't showing signs and driving with +B/FP jumpered didn't affect driving performance, I probably wouldn't bother to change it out or upgrade capacitance either. But then I'm relatively new to the world of (small) circuits anyway, still got loads to learn!

Outsane

great info thanks for sharing.. I am going to have to pull the relay out of the trash

MudHippy

Well, I guess they aren't all as cheap as the one for my 88. RockAuto has them listed as a Fuel Pump Relay for $38.79(+ shipping). The one they have for your 90 4Runner is $69.79(+ shipping).

http://www.rockauto.com/catalog/moreinfo.php?pk=39237

Oh, and my reason for questioning the use of solder on the contacts is because it's a much softer material, with a lower melting point. Like you're saying, the contacts are very durable. I just can't see how solder, being used for the same purposes, is going to be. It may work...but for how long?

jbtvt

True, and I wouldn't necessarily use it on other relays, but the capacitor in this circuit acts as a buffer. So when the circuit is opened, rather than a sudden cutoff with full voltage still trying to pass through the contacts as they spring open resulting in an arc, the contacts open slowly (at least to an electron) as the capacitor discharges itself through the coil and resistor, and the chance of arcing is greatly reduced, if it exists at all.

I haven't had a reason yet to test solder in COR contacts yet, and I wouldn't go to the trouble unless a little sanding didn't cut it, but as long as there is a good amount of the contact's surface area touching (reducing potential heat-generating resistance), in the COR circuit I believe it would be fine. I probably should have specified that though.

EDIT - I was mistaken about the mechanism by which a cap/resistor in parallel actually suppress a spark. Smaller gaps=smaller arcs, but apparently the actual elimination has more to do with the current choosing the path of lesser resistance, into the capacitor, and the cap recharging itself and soaking up the arc. See http://www.okaya.com/images/noise/1200.pdf for more info. Think I was inhaling too many welding fumes yesterday