Skip the auto shop - Our mechanics make house calls

Q: Relay for engine management doesn't work unless the magnetized plate is pushed in. Please help!

asked by on

I tried to jump power from fan fuse to engine management fuse and it sparked then wouldn't start.. found that pushing magnetized plate in it would. Start ... put in a good working relay and it still needed to b pressed for constant power.... what would cause a relay to not work unless engaged manually... Please help i am in need of assistance ....

My car has 200000 miles.
My car has an automatic transmission.

A: Generally speaking, there are two separate ...

Generally speaking, there are two separate circuits inside of a relay. One circuit is, what I’ll refer to for the sake of this writing, as the "supply" side, and the other is the "signal" side. The supply side has a positive and negative post, and is what supplies voltage to the component being controlled, by way of the switch inside the relay. The signal side also has a positive and negative, but the signal side is what actually commands the switch inside the relay to close, and allow voltage to flow through the supply side. This is the reason there is typically four posts on a relay.

If you have to manually push the switch closed to get the circuit to work, then something is keeping the supply side from getting the signal necessary to close, and allow voltage to flow through the supply side. Without knowing the model of the vehicle, I’m not sure if the computer controls the voltage, or the ground, to complete the circuit.

You would need to get a wiring diagram and test the individual pins in the fuse box to see if there is a voltage or ground signal that isn’t being supplied when commanded. Once you figure out what signal is being received, then you have to figure out why. These situations are where a certified mechanic becomes valuable. If you would like to have this taken care of, a certified professional from YourMechanic can come to your car’s location to inspect the electrical system and proceed with the proper repairs.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Hi - Knocking noise

Hello. If there is a knocking noise then it may have some bad fuel or it may be another failure like an internal engine problem or a bad sensor. I usually start the diagnostic process by scanning the computer for...

Q: Interior lights won't turn off

Hello. It sounds like you may have a short in your electrical system somewhere. I would recommend having your electrical system inspected by a qualified professional in order to determine where the short is located. This will include loading up...

Q: Investing cosmetically in Mitsubishi Galant

Don't put too much money in it cosmetically, because Mitsubishis are decent cars, but in the long run, they do not hold up like Toyotas or Hondas. It's not a car that can last 20 or 30 years like Toyotas...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.