2007 HHR 1LT , hatch keeps taking out the relay but not blowing the fuse. I have gone through three relays. Could be bad latch? Latch works fine when relay is changed for 10 to 15 times then have to change relay.

Any ideas?
Thanks

 

Which side of the relay fails?
Is there a fuse in position #11 underhood?
What happened just before the first time this happened?
Do the pins on the failed relays show signs of burn/spark/wear?

 

A bad ground wire. Or bad soft touch switch

 

Being an electrical engineer for decades and dealing with relays often, I can say that 99% of relay failures occur on the switched side (contacts).

The control side of the relay is designed with a certain impedance to allow the control voltage to turn it on without drawing excess current. The only way to burn out the control coil is to apply a higher voltage, which is unlikely in this case, or the touch switch sticking on which doesn't appear to be the case because you say the relay works for 15-20 times. If it was sticking on, the hatch would refuse to lock shut. The reason sticking on might destroy the relay is that these are usually "intermittent duty" relays which can only be on for a short period before the coil would overheat. Fuel pump relays are "continuous duty" relays which are designed to be on all the time without burning out the control coil.

The lock actuator could be drawing excess current for some reason (partly shorted coil, etc). This is what was happening to my shift solenoid in another post of mine. The excess current would eventually degrade the contacts.

as Donbrew said, find out which side of the relay fails. Take the failed relay and apply 12V to the control side. Do you hear the relay click? If so, then contacts have failed.

Steve

 

Ok, so I looked at the schematic of the liftgate release circuit.

The touchpad goes to the BCM. The BCM then activates the liftgate release relay (by grounding it). Highly unlikely the touchpad could take out the relay in this design.

What I did notice is that the liftgate release motor has a suppression diode across the motor terminals. The purpose of this is to suppress the "back EMF" that occurs when you shut down any device that has a coil in it. When you turn off the motor, the magnetic field that has built up in the motor coil will instantly collapse, generating a reverse voltage across the motor terminals that could approach thousands of volts. This is exactly how an ignition coil works to generate voltage to the spark plugs. Without the diode, this would cause a large arc across the relay contacts. If the suppression diode is bad I guarantee you this would cause the problem you are having. Not saying that's what is happening here for sure, but a likely suspect.

The only way to check this is with a voltmeter that has a diode-check setting. A regular digital voltmeter won't activate the diode so it will appear bad even if it's good.

Steve

 

If the actuator is shorted out, send hellshotrod a PM . They are available but pricey!

https://www.rockauto.com/en/catalog/...actuator,13397

 

Actually, we went through the electrical symbols in another thread recently. That is not a diode it is a resistor the does the same thing. On both the relay and the motor.

I can't see anywhere that could overload anything. I suppose if you hooked a second battery up you could force a 12V relay to fry. That is why I asked about the pins on the relays, I am leaning toward a bad connection inside the fuse box.

Maybe somebody spliced into the wrong wire for an after market radio or LED.

 

Thanks for all the ideas I hopefully will have some time next weekend to check it out. I have not had time to check it electrically, I used some southern ingenuity on it and rigged up a way to open it with the emergency release mechanism.
I believe it is probably a faulty switch in the handle, not sure why they chose to use an electrical switch instead of a mechanical handle in this application.

 

Because it was all the rage and pretty cool, back then.