I just installed a SPST relay to switch my car for map switching capabilities for a tune...It was working the first day, and now its not working...Wanted to know what the chances are the relay has gone bad...Its seems like its a universal relay of 14vdc with 30a...I have a diode hooked up to it to...Before I go out and buy another relay, I just want to know what the chances of a defective relay can be...I heard that they are pretty rigid and most often never go bad, is this TRUE? Thanks for the time to help out...I am new to the game of wiring with relays and diodes...
Usuallly good for about 15 million cycles. So check your wiring connections and fuses. Never in 40 years had a failure unless it was my wiring error.
Can a Diode be hooked up to the point where it shorted the relay...Also its looks like a cheap relay and I know its almost impossible can it be possible I have one in a million that is defective...How can I check to see if this relay is indeed not working...should I open it up to check the internals.....
First thing you can do is check the voltage on the relay. From pin 85 to pin 86 with the switch in the "ON" position you should have 12vdc.
When you turn the switch from on to off and from off to on can you hear the relay click?
If you can hear the relay click then your pin 85 and pin 86 are OK. If you can't hear the relay click and you have proper voltage then your relay is bad.
If you can hear the relay click and the system still isn't working then you can use an ohm meter to check the relay. With the switch off you should have ~0 ohms from pin 30 to Pin 87A and you should have infinite resistance between Pins 30 and 87. Switch the switch in the "ON" position you should have ~0ohms from Pins 30 to 87 and infinate ohms from Pins 30 to 87A.
If this check works our your relay is fine and your wiring is wrong. If it doesn't check out replace the relay.
I've seen relays fail occasionally in industrial applications but very, very, very rarely (if ever) in a car.
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Kevin Pierson
Ref the diode. Have you placed it across the relay coil terminals 85 and 86. the normal convention is 85 is neg side and 86 pos so the diode's band goes to the pos side, although if you'd done that wrong it wouldn't have worked initially, if it worked initially follow KP's advice.
cn555ic wrote:
Can a Diode be hooked up to the point where it shorted the relay...
No! Any short protects the load it is shorting.
One of my favourite "reasons" for blowing bulbs in cars etc is "there must be a short somewhere".
No no no! Except where the short causes cyclic cooling/heating of the bulb by robbing its power - which is fairly unlikely - or it the short bypasses dropping resistors etc (6V bulbs i 12V systems; LEDs etc).
Bulb blowing is usually vibration or intermittent contact (hence "thermal vibration" or cycling), though it can be over-voltage also (regulation, spikes, etc).
The same applies to most loads including relay solenoids (natural life-cycle aging excluded.)
In short (pun intended), no extra connection or device will cause MORE power through a load (assuming passive devices - not batteries or caps etc, nor bypassing voltage/current limiting devices).
If a relay's spike protection diode is connected the wrong way (as I saw described at another site), the diode will fry - not the relay.
As for testing the said relay, most auto relays can be heard clicking. The only relay failures I have had are from water leakage. (And contact arcing in rare AC situations.)