pcm and electric fan
Thread Starter
Staging Lane
Joined: Jul 2008
Posts: 72
Likes: 1
pcm and electric fan 1948 Chevy 5 window pickup with 2007 Classic 5.3/4L60E conversion. Have started engine several times. Last time ran engine smoothed out and ran for about 5 minutes. Single speed Spal electric fan did not come on. Fan is wired with relay triggered by green wire 42 from blue plug group. Does pcm provide ground or positive to relay?
Thread Starter
Staging Lane
Joined: Jul 2008
Posts: 72
Likes: 1
Ecm #42 fan wire My single speed Spal electric fan is not turned on by the ecm wire #42. I get a 14 volt reading on wire #42 instead of the negative signal needed to turn on the relay. Using a a Bosh 40 amp 4 pin relay. Do I have it wrong?
That should be right the way you have it, but never seen 14v on that wire before. Are you positive you're on the correct pin? You could try manually grounding that wire to make sure the wiring is correct just in case.
Also, the fan on temps are pretty high on a factory tune, so it may have not reached the operating temp yet.
Also, the fan on temps are pretty high on a factory tune, so it may have not reached the operating temp yet.
Last edited by ls1nova71; Jul 27, 2016 at 10:34 PM.
We can only assume from information provided, that OP has verified this is the wire that is trying to do what he wants...
OP, a little background, what ECM/wiring harness are you using? Also, do you have relays built into the fuse box, and who's box is it?
T,
Last edited by TomM; Jul 28, 2016 at 08:24 AM.
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On The Tree
Joined: Sep 2007
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You are fine seeing a positive voltage since your computer hasn't triggered the wire to ground out your relay. As mentioned above you can manually ground that wire while it's hooked up to your relay to assure that you have wired the relay correctly. Your relay will show a positive voltage until your ECT's have reached the temp to trigger relay. This is all adjustable in the tune. You also have to make sure the computer is properly programmed for electric fans. Some of the earlier PCM's had mechanical fans only and electric fans aren't enabled in the tune from the factory. So many variables at play here.
E38's also use a ground trigger for relay. I believe the only +12v relay trigger GM uses is for Fuel Pump relays.
E38's also use a ground trigger for relay. I believe the only +12v relay trigger GM uses is for Fuel Pump relays.
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Thread Starter
Staging Lane
Joined: Jul 2008
Posts: 72
Likes: 1
2007 Classic 5.3/4L60 L59 Flex fuel This is an L 59 flex fuel engine. No mechanical fan, two electric fans. The computer green and blue plug ins. I don't know how to tell the ecm model, so I will post some of the numbers on the ecm. I pulled everthing from the wrecked 4 door crew cab pickup with less than 7,000 miles. With help from Brendon's website I modified the harness.
Delphi J1 Blue
C 40 26407
Service #12602802 YKYY
86YKYY926128 GX W6
12587118
H.W.D. NO. 12589172
Delphi J1 Blue
C 40 26407
Service #12602802 YKYY
86YKYY926128 GX W6
12587118
H.W.D. NO. 12589172
My ecu is out of a 2008 Vette - supplier says ground is supplied on one wire for fan on at 226F, off at 220F. The other ground supplied/fan on at 235F, off at 229F. So things get pretty toasty before anything happens.
From a GM website...
This product fits 47 vehicle variants.
Buick: 1 models, 1 variants for 2004.
Chevrolet: 9 models, 34 variants between 2003 and 2007.
GMC: 4 models, 4 variants between 2006 and 2007.
Hummer: 1 models, 8 variants between 2003 and 2007.
What did you use as a schematic/pin out? As Mr. Yount said above, you probably didn't get warm enough to trigger the relay. You are on the right track with the wire you have. You should have a key on, fused hot wire to the relay, and the 43 wire to ground on the relay, that should do it.
Would have to see a tune file to know where the temps are set, but stock, they are high..
T,
This product fits 47 vehicle variants.
Buick: 1 models, 1 variants for 2004.
Chevrolet: 9 models, 34 variants between 2003 and 2007.
GMC: 4 models, 4 variants between 2006 and 2007.
Hummer: 1 models, 8 variants between 2003 and 2007.
What did you use as a schematic/pin out? As Mr. Yount said above, you probably didn't get warm enough to trigger the relay. You are on the right track with the wire you have. You should have a key on, fused hot wire to the relay, and the 43 wire to ground on the relay, that should do it.
Would have to see a tune file to know where the temps are set, but stock, they are high..
T,
Thread Starter
Staging Lane
Joined: Jul 2008
Posts: 72
Likes: 1
Fan low speed turn on I used the "LT1 swap" web site for my pin out info. Also had Brendon reprogram my PCM. So, if every thing is wired correctly the wire 42 signal will be 12 volts until the engine temperature reaches the preset "on" signal in the tune, then the signal changes to ground and turns onthe low speed fan.