ECM cooling fan pin current limit ?
ECM cooling fan pin current limit ? I would like to use the fan on/off output (high and low) to drive some heavy duty bosch relays that will pull about 290ma. Will this burn out the transistor that drives that output?
Thanks in advance
Thanks in advance
Yes, I understand that.. When the pin(s) ground, they provide the ground to a circuit that consists of a relay and a +12v source. The coil of the relay has a certain resistance. The amount of resistance determines how much current the relay coil will draw. This current will be seen at the pin. too much current draw will damage the transistor that drives the pin. I just want to be sure that the heavy duty bosch relay doesn't exceed the safe current limit for the ecm.
The PCM doesn't really care what your relay is outputting. The relay is energize as described above on the low current side which inturn energizes the coil to the high current output. I am not sure what you are looking for? The relay does not back feed anything to the PCM if that is what you are worried about.
Thanks for the post LT1Bird, but you're not quite following.
12secSS- I'm hoping you're right (that the pin can drive up to 1000ma (1amp)). I think I'll be ok with the 290ma draw of the relay I want to use. The stock relay probably doesn't pull much less than that. Wish me luck!
12secSS- I'm hoping you're right (that the pin can drive up to 1000ma (1amp)). I think I'll be ok with the 290ma draw of the relay I want to use. The stock relay probably doesn't pull much less than that. Wish me luck!
Trending Topics
On The Tree
Joined: Nov 2007
Posts: 130
Likes: 0
FDLS6.. I assume you are going to replace the stock relays with the new ones. other wise you could use the 12V to the fans from the stock relays to pick your new ones.. or you could always leave the stock relays in place and use them to pick your new ones (injects extra failure points to worry about if something breaks) . Another thought the high speed pick blue wire (0 volts) from the PCM actually picks two relays (2 & 3) so the driver may have enough load tolerance to pick your bosch. If you have a multi meter with a amperage setting you could stick it on the green (low speed) and then the blue (high speed) lines and see how much current the picks are drawing blue will be 2x the green. I believe the stock relays draw about 175 -200 MA as the coil R= about 70 ohms and I=E/R. here's a schematic from shoebox http://shbox.com/1/fan_schematic_1995.jpg
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo Thanks bobdec. You're on board with my question. I have the 2000 ls1 computer in my rx7 and do not have the factory relays. I wouldn't want to piggy back anyway. Thanks for the ballpark resistance on the oem relay coil. That gets me the info I need to feel better about the aftermarket realys I'll be using. The largest one would be around 40ohms/290ma. I'm good to go!
wire it in series, that way the circuit will experience a higher resistance than instead of lower. you'll know it'll be safe that way, and probably easier to diagnose later on should something go wrong.
i take it you only have one cooling fan so you are wanting to utilize the other circuit for something else?
i take it you only have one cooling fan so you are wanting to utilize the other circuit for something else?
Last edited by slowpoke96z28; Feb 12, 2009 at 07:11 PM. Reason: curious as to what the OP is doing, lol
