Notices
GMT 800 & Older GM General Discussion 2006 & Older Trucks | General Discussion

Wiring diagram for PCM harness

Thread Tools
 
Search this Thread
 
Old 08-08-2005, 11:34 AM
  #1  
12 Second Truck Club
Thread Starter
iTrader: (5)
 
white1's Avatar
 
Join Date: Apr 2005
Location: Sittin on jackstands
Posts: 5,230
Likes: 0
Received 4 Likes on 2 Posts
Default Wiring diagram for PCM harness

Anyone have the wiring diagrams for making your own E-fan harness? I have one, but thinking of making one for the PCM to control. What are the relays for? I figure one is for the A/C on, but what are the other two? Thanks
Old 08-08-2005, 11:42 AM
  #2  
Launching!
 
OKLAGMCRUISER's Avatar
 
Join Date: Mar 2003
Location: TULSA
Posts: 209
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by white1
Anyone have the wiring diagrams for making your own E-fan harness? I have one, but thinking of making one for the PCM to control. What are the relays for? I figure one is for the A/C on, but what are the other two? Thanks
I had to make one for my a/c...using the pcmforless harness. I merely used a relay to change a pos to a neg and used the manual switch wire from bryan's harness to one side of the relay and the dark green wire from the a/c to the other side. Works flawlessly. As for the other two...I have no real idea.

Pat
Old 08-08-2005, 03:04 PM
  #3  
High on diesel fumes
iTrader: (70)
 
thunder550's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 12,658
Likes: 0
Received 3 Likes on 3 Posts
Default

Just a guess here...but I think one is switched on when the PCM triggers, one is switched on when the a/c triggers, and one is switched on when both other relays are switched on.
Old 08-08-2005, 04:20 PM
  #4  
TECH Resident
iTrader: (1)
 
Okie5.3's Avatar
 
Join Date: Aug 2004
Location: Oklahoma
Posts: 871
Likes: 0
Received 0 Likes on 0 Posts
Default

the relays are allowing you to use a lower power control signal to power something that requires much more power and not have to run long lengths of wire that is moving lots of current, where you get into resistance, heat, not so good performance, etc...

i drew up a simple diagram when i installed my fans using 3 relays. 1 relay each for the fans and another relay using the A/C compressor signal to run a single fan. it was a high-speed only, both fans would run when reaching the temp setpoint. if the A/C was on a single fan would run unless it reached the temp setpoint and then the other fan would start. when the temp fell below the setpoint and the A/C was still on only 1 fan would shutdown, and of course both would shutdown if the A/C compressor wasn't energized.
Old 08-08-2005, 07:46 PM
  #5  
12 Second Truck Club
Thread Starter
iTrader: (5)
 
white1's Avatar
 
Join Date: Apr 2005
Location: Sittin on jackstands
Posts: 5,230
Likes: 0
Received 4 Likes on 2 Posts
Default

Thats helpful. I know what a relay is for, but I'm sure some people dont. I didn't think of that though. I guess I'll draw something up tomorow at work. Thanks
Old 08-08-2005, 09:03 PM
  #6  
TECH Addict
iTrader: (6)
 
SnakeOiler's Avatar
 
Join Date: Aug 2004
Location: F'burg, VA
Posts: 2,417
Likes: 0
Received 4 Likes on 2 Posts
Default

I did these when I put mine in:
2-relay

3-relay

the pictures are kinda big, you might want to print them out.

Last edited by SnakeOiler; 07-30-2006 at 04:40 PM.
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Porscharu914
GMT 800 & Older GM General Discussion
14
01-20-2016 10:45 AM
kalikid06
Tuning, Diagnostics, Electronics, and Wiring
2
09-13-2015 05:48 PM
97gmc
Tuning, Diagnostics, Electronics, and Wiring
22
09-08-2015 10:56 PM
muncie21
Tuning, Diagnostics, Electronics, and Wiring
2
09-07-2015 09:55 PM
Alvin@PCMofNC
Sponsor's Announcements, Sales, and Specials
0
09-03-2015 06:38 AM



Quick Reply: Wiring diagram for PCM harness



All times are GMT -5. The time now is 09:54 PM.