Ignition Relay
Thread Starter
Launching!
Joined: Nov 2020
Posts: 231
Likes: 280
From: San Antonio, TX
Ignition Relay I have run into the "turn key, everything is good except no crank"...security light does go away so not VATS....I have replaced ignition coil and am now moving on to ignition relay and then starter....there are several different Amperage relays to choose from for the ignition (30,35,40)...what amperage do I go with? Is it possible to get too high of amp rating on relay? Is there a benefit to having a higher Amperage rating? I believe the ignition fuse is 50 Amps but just wanted to ask and see what others say.
Thanks
Will
Thanks
Will
Joined: Nov 2003
Posts: 11,328
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
Relays are rated for the maximum current they can pass. It's mostly based on the resilience of the contacts on he high current side of the relay. You can use any relay which at least meets the needs of the circuit. Higher than necessary ratings will not not affect usage - most 30 amp relays never see anything close to 30 amps of current - but they will generally cost more and can be harder to find. Higher rated relays will last longer but standard 30 amp relays are pretty reliable these days and will last many years under normal use. This is different from fuses where you never want to use a fuse that is rated higher than the original.
Before buying relays, you should check if that is the cause of the problem. Throwing parts at a problem is never the correct way to fix it. Try swapping one of the fan relays in the other junction box for the starter relay and/or the ignition relay. If it then starts, you'll know the relay was the problem. Otherwise, you should look elsewhere. There are all kinds of simple tests you can do to narrow down the cause of a no crank problem without buying more parts.
Before buying relays, you should check if that is the cause of the problem. Throwing parts at a problem is never the correct way to fix it. Try swapping one of the fan relays in the other junction box for the starter relay and/or the ignition relay. If it then starts, you'll know the relay was the problem. Otherwise, you should look elsewhere. There are all kinds of simple tests you can do to narrow down the cause of a no crank problem without buying more parts.
Staging Lane
Joined: Feb 2016
Posts: 70
Likes: 6
A little something to keep in the back of your head. The VATS portion of my BCM failed. Proper resistance measured at the BCM header, P1626, no crank. Deleted VATS in HPTuners, which got the fuel pump to run.....but still no crank. The negative side of the starter relay coil runs through the BCM and is grounded when the VATS circuitry is happy. Ended up having to cut the wire at the BCM and grounding it to get the starter relay to close.
Thread Starter
Launching!
Joined: Nov 2020
Posts: 231
Likes: 280
From: San Antonio, TX
A little something to keep in the back of your head. The VATS portion of my BCM failed. Proper resistance measured at the BCM header, P1626, no crank. Deleted VATS in HPTuners, which got the fuel pump to run.....but still no crank. The negative side of the starter relay coil runs through the BCM and is grounded when the VATS circuitry is happy. Ended up having to cut the wire at the BCM and grounding it to get the starter relay to close.
Staging Lane
Joined: Feb 2016
Posts: 70
Likes: 6
That would have been my next suggestion. I had a weird issue when it got cold.....below like 40 degrees. Turn the key on and nothing would respond. Accessories worked fine so it wasn't the BCM. No dash lights, no CEL, no ignition.....but would crank. Had to wait like 10 seconds with the key in RUN for everything to wake up. Sometimes the NEXT time you fire it up (like a coffee run), when you let go of the key it would stall with a backfire. Turns out the contacts in the ignition switch were failing......the stall/backfire I presume was from the contacts bouncing open when the key was released. Changed the switch and both problems are gone lol
