24v relay question

[WAGNUM]

Got my 4L80e swap done! Drove the truck yesterday, ran great. Today I went to drive it and the TCM (Quick 4 aftermarket) wouldn't turn on. Turns out my 24v 30amp relay isn't working. My only guess is that 30amps must not have been enough? Does anyone know what amperage is correct for the relay that switches on the TCM for the 4L80e? I read in AUGI's post that he bought a relay from thehummerpartsguy.com but he doesn't say what the amperage is. Looks like his relay is gray but can't see it very well in the picture. My guess is I need a 24v 50amp relay.

The below pic is what I currently have. Should have read the "Warning label" on the bottom line of it...


In case you're wondering, I ran a wire from my ignition switch to the relay to supply the "switched 24v", then have 12v power into the other side of the relay. Turn HMMWV to "RUN", 24v power is supplied to the relay, energizes the coil, moves the relay's contact to "ON", 12v's is supplied to the TCM and turns it on. Like I said, it all worked great yesterday...

Would this Bosch relay work?

 

[BLK HMMWV]

Hi Not sure this is anything helpful.
I was running an after market trans controller before I took the plunge and separated the body from frame and switched out the main body wiring harness.
I was running a different controller then you. I used the TCI EZ TCU. I just went and dug up the old relays I used and they were 30A 30V DC relays.

The military controller has a 20 amp resettable circuit breaker in the circuit feeding the controller via the relay so I doubt you would be drawing more then 18 amps.
Send me a PM with your email addy. I will send you a PDF of the HMMWV 4L80E trans tech manual.

Sorry that's all I can do
BH

 

[WAGNUM]

Sounds like I shuda used 30v relays instead of 24v. Do you think since HMMWV's are actually around 27v or 28v that my "CHYNA!" (my Trump impression...) made relay couldn't handle it? Jon in TX has the same setup as me and recommended using a DC/DC Converter ($19 on scam-a-zon). Says he's never had any issues, so I got one coming. Appreciate the help BH, that manual would be a good resource.

 

[BLK HMMWV]

Not sure, my relay was made in Japan . Woo hoo.
Check your email.
I think I have an extra relay in case you need it.

Ted Gates from over on the G503 board was kind enough to send me that PDF of the trans manual.
That board also has a HMMWV section
Best of luck
BH

 

[Augi]

I wouldn't recommend using a DC/DC converter to power your TCM. It's another complicated thing to break and likely won't be in a harsh environment enclosure. It'll work for a while, but who knows when it will kick the bucket.

The TCM draws a couple of amps max. I wouldn't be surprised if it was under one. There is no need for a massive 30a or 50a relay to power it. If it needed big current, the harness conductors would be huge to handle it.

Generally if a relay is rated for "24v", it'll go up to 30 or so. You can look on the data sheet and it will tell you the coil resistance and the expected current draw. They should have some maximum values listed and you can do the math to figure out the maximum voltage.

Augi