marlinspike

How can I test the pictured relay to see if it's the reason the A/C won't engage?

Mau5head

put sand in it then wrap it in bacon. if that doesnt work blame allah jackoffasourus

Computer_Nerd

i was gonna write it out, but here's a visual via youtube video.

no need to take the battery out of the car, just make sure you can hit the terminals and listen for the click, sounds like a queer snapping his fingers.

[youtube]3JB63ebFfgU[/youtube]

marlinspike

There isn't simply a pair of terminals on the car side that I can jump that would make the car think the relay was switched on? I was thinking maybe 3 and 1? I don't think the test in the vid works with a time delay relay (because I'd need an electricity source to heat up the time delay circuit...I think).

Fabrik8

Pins 4 and 5 are the relay coil, which is where you want to apply 12V power to test if the relay is turning on or not. That is what switches the relay. Pins 1 and 3 are the relay contacts, which is what you want to check resistance across when the relay is switched. I'm not exactly sure what is in the relay to make it time delay, but I'm assuming that it's a bi-metallic element that heats and cools depending on whether power is applied or not (similar to how many turn signal flasher relays work).

You should check that schematic and see which terminal on the relay coil goes to ground, and which goes to 12V. Most relays don't matter, and will work either way because the presence of the magnetic field (caused by current through the relay coil) is all that matters. However, some relays have things like flyback diodes built in to the coil, so it's wise to pay attention to terminal polarity just to be safe. You have the schematics so it's easy enough to see what goes where.

marlinspike

Yes it is.

And 5 is ground.

I had no idea that's how turn signal relays work though. That's pretty awesome. Bi-metallic strips are all over this car, even in the fuel injection.

Fabrik8

Not all turn signal relays work like that, many newer cars are controlled by the body controller to turn on/off/on/off and are just a regular relay. That's the much better way to do it IMO, and the flash rate isn't dependent on the load so it won't blink relay fast if a bulb blows out. Thermal flashers have a lot of drawbacks...

So apply 12V to term 4, apply ground to term 5, and check continuity across 1 and 3. If you get anything but a really low resistance across the switch terminals (1 and 3), the contacts are corroded, eroded, or have insulating carbon deposits on them.

marlinspike

I always thought the fast blinking was a nice feature - let's you know that you have a burned out bulb without having some ridiculous LED display in your instrument cluster.

marlinspike

Easier said than done...I don't have any alligator clips

Fabrik8

Sadly, I can't help you at all with that one. But Radio Shack can.