Dave Hacks

Why hack a Bosh Style automotive relay?  Because you went to the auto parts store, and bought a Normally Open (NO) relay thinking it was a Normally Closed (NC) relay, Radio Shack is too expensive far away, and you don’t feel like getting blank stares from all the rednecks at the nearby automotive stores when you ask if their poorly labeled products are NO or NC.

So here we go, a cheap ($6?) Bosch style relay.  I painted the top silver so you could see it better.

Before that, I would like to apologize for all the poor pictures that follow.  My wife confiscated the good camera to take pictures of the baby, so I am left with my old digicam that thinks ‘focus’ is a crappy car from Ford.

In my defense, I could not read that diagram through the package, and the package was not labelled.

Next, I cut the casing off, which was oddly easy.

The exposed innards.

Another, not much better, look.

Next I tinned up a piece of wire.  Don’t ask me the guage, maybe 16?  I started with some 12, but it was too thick to clear the contact arm in the relay, so I found this on the parts bench and used it.

Tinning the wire.

And then it was snack/play time…

Tinning a ‘shmallow.

After I was done burning random objects, I trimmed the tinned wire and squished both ends  at perpendicular angles to better fit onto the contact plate and the brass post thingy.  That brass post is just originally used to keep the contact arm in check when at rest.

Test fit wire.

The little flat contact that was sticking up was bent down, and after everything was deemed to be acceptable, I removed the little brass post, after marking it to indicate where it cleared the plastic, and got ready to solder it on.  For this and the bent down contact I roughed them up with some fine files and added a touch of flux.

Brass post, ready to be soldered.

Unfortunately, I don’t have pictures of the solder-up as poor lighting and a crappy camera were working against me, but I have pictures from after.  (These pictures were taken with my <$15 macro camera)

Brass post with wire soldered to it.

Wired to the contact.

If you want to see how to make the camera that took these pictures, check out my Cheap Macro Camera post.

In conclusion, this went pretty well.  The relay works, and with the top glued back on you can’t tell a difference functionality wise between this and a normal relay.  Some areas of caution, however, would be longevity and safety.  Longevity wise, I think that not having a ‘stop’ when the relay is triggered would cause undue vibration and stress and eventually wear this relay out faster than normal.  Also, I would not trust this relay up to its rated 30A.  I mean, I probably would, but I am crazy.  If I were you, I would not trust this in an application where safety or reliability were a concern.  I used this particular relay for testing another project, but am going to purchase appropriate relays for the final product.