couple relays rattling/clicking while in D

[BladeX10]

This just started happening... When i put the car in D, Theres a fairly loud rattling/clicking coming from the engine. I tracked it down to the fuse boxes and pin pointed the relay, i pulled it out and then another relay will start rattling.. took the next one out, which controls the headlights, then another started rattling. What is going on? Is it safe to drive? Its a 1998 Prizm.

[BladeX10]

Nobody knows anything?

[KeMBro2012]

ghost in the machine, man, ghost in the machine... you've got a short or a loose connection somewhere and the added vibration of the transmission dissipating the engine's torque when in drive and not moving is probably exacerbating the issue. Of course, without seeing it for myself, I can't really bring myself to believe that it's really behaving that way.

Are you positive it's a relay and you don't have something loose that you think sounds like a relay? It would be a one-in-a-billion series of shorts and loose connections that would have to be spaced exactly right in relation to each other, with the exact right voltage flowing through your electrical system, such that one pair of leads would be close enough to short, while the others were not; when you remove the one relay having the issue, the voltage increases ever so slightly and the next pair starts to short, so on and so forth.

That's not happening, no way, no how, because the voltage in a car's electrical system varies so much from one moment to the next, vibration prevents contacts or stripped wires from staying the exact same distance from each other, and a number of other factors which make this such a physical improbability as to call it impossible.

Check for anything loose; check every mount, every nut, every bolt, every cap, everything you can reach and some stuff you can't. If it was just one relay, I'd say replace the relay and be done with it; it's not a relay issue.

[BladeX10]

Its definitely the relays, you can feel them making the noise. Its not a single relay, its a couple going at once i discovered. Sometimes it doesnt do it and ill drive for a couple miles and they will do it. Its weird.

[KeMBro2012]

Back to my first line, then. Ghost in the machine. Good luck tracking that down.

Check all your grounds; disconnect them, clean the contacts, reconnect them. Your likely culprit, if it is indeed relays, is a dirty or loose ground.

[BladeX10]

Ill check out the grounds.. How many grounds are on these cars?

[KeMBro2012]

I haven't had a chance (or reason) to dive into the eletrical system in my corolla yet, so I can't say with any certainty; someone else will have to chime in. The engineer in me wants to say one per box, though; so there should just be one ground for whatever box the relays are in.

[BladeX10]

Im back with an update i guess.. Well i messed around with the grounds and didnt see any loose ones or broken ones. I did notice that the 2 fans werent working but occasionally turning on. the left one(passenger) fan would spin when i reved the engine and would stop when i let off then the relays would click and act up while the right side fan moves a couple inches at a time and so did the left one. Yesterday both fan were on when i cold started the car.

[BladeX10]

I also discovered the fans both come on before starting the car, they come on when the car powers up before starting.


EDIT: if i unplug the pressure switch, both fans stay running while the car is running and if i plug it back in, the fans start tripping out and the relays start clicking and rattling and the car starts running alittle rough. So i discovered the cause to my original post i believe

Edit again: if i play around with the sensor for the passenger side fan, it shorts both of them out to turn off and on along with the rattling relays in the box. Im confused as to what the problem is.

[KeMBro2012]

I'd try replacing that sensor. It's unrelated, but at the same time if it's shorting out somewhere it could be confusing the ECU.

[BladeX10]

Today i drove close to 100 miles with that sensor/switch unhooked and it ran great.. the fans stay on constantly but its not shorting out and no relay chatter or lights flickering.

[KeMBro2012]

Hmm... yeah, I'd replace that sensor, then...