Idle drops when ac gets turned on - RX7Club.com - Mazda RX7 Forum

3rd Generation Specific (1993-2002) 1993-2002 Discussion including performance modifications and Technical Support Sections.
Sponsored by: Elite Rotary Shop

Idle drops when ac gets turned on

Reply

 
 
Old 07-09-10, 12:19 PM
  #1
Junior Member
Thread Starter
 
BlackSun's Avatar
 
Join Date: Dec 2008
Location: ATL
Posts: 30
Thanks: 0
Thanked 0 Times in 0 Posts
Idle drops when ac gets turned on

The tittle says it all. my idle is around 900 to 1k and when i turn the ac on the idle drops and the engine stalls. haven't had any luck looking for the ac idle switch. i have a FC commander. besides that the engine runs well no other engine porblems.
BlackSun is offline  
Reply With Quote
Old 07-09-10, 12:40 PM
  #2
Junior Member
5 Year Member
iTrader: (7)
 
Join Date: Apr 2010
Location: Las Vegas
Posts: 39
Thanks: 0
Thanked 0 Times in 0 Posts
How the condition of the engine. I know when mine went bad it would run but when I turned on the AC it would die. My vacuum was around 10 in/hg
REDgen3 is offline  
Reply With Quote
Old 07-09-10, 12:52 PM
  #3
NEVER GO FULL RETARD
iTrader: (1)
 
Montego's Avatar
 
Join Date: Apr 2001
Location: San Diego, CA
Posts: 6,053
Thanked 2 Times in 2 Posts
one thing to check is your AC lines. If they are bent it can cause idle issues. I know it's crazy weird but it does happen.

I bent my AC lines one day while removing my stock duct. The end result was my idle was really crappy whenever I'd turn on the AC. As soon as I bent them back problem disapeared. A couple of years later I read the exact same issue and fix from a fellow forum member so I'm not alone in this.
Montego is offline  
Reply With Quote
Old 07-09-10, 01:38 PM
  #4
MODERATOR
iTrader: (137)
 
Alex Rodriguez's Avatar
 
Join Date: Jan 2005
Location: Houston Texas
Posts: 6,430
Thanked 0 Times in 0 Posts
Check your ISC unplug it and then turn your a/c on see if It stalls
Alex Rodriguez is offline  
Reply With Quote
Old 07-09-10, 02:00 PM
  #5
wannaspeed.com
10 Year Member
iTrader: (23)
 
Dudemaaanownsanrx7's Avatar
 
Join Date: Feb 2003
Location: Texas
Posts: 2,802
Thanks: 0
Thanked 0 Times in 0 Posts
Originally Posted by Alex Rodriguez View Post
Check your ISC unplug it and then turn your a/c on see if It stalls
What i was going to suggest.

Most likely the ISC (idle system control). You can also raise your idle as a temporary fix, or permanent if you don't mind idling at 1000.
Dudemaaanownsanrx7 is offline  
Reply With Quote
Old 07-09-10, 03:29 PM
  #6
Recovering Miataholic
 
wstrohm's Avatar
 
Join Date: Mar 2002
Location: Fountain Valley, CA
Posts: 1,423
Thanks: 0
Thanked 0 Times in 0 Posts
The RX-7 has an "Electrical Load Unit" which is located close to the PCME. Its wiring is shown on page Z-30 of the 1994 workshop manual. It receives inputs from the instrument cluster, combination switch, heater control unit (fan switch), and CPU No. 1, and outputs a signal to the PCME on its terminal N to the PCME's terminal 3B. The ELU is supposed to let the PCME know the number of electrical loads engaged so the PCME can adjust the idle to compensate. On our '94, idle speed when warm with A/C off is 720 rpm, but when A/C compressor is engaged, it jumps up to 1000 rpm. There is an A/C sensor inside the Heater Control unit (see pages Z-68 ("Ga") and Z-70 ("Gb") for the circuits that affect the input to the Electrical Load Unit on the orange/blue wire that runs through connector X-15 (circled "27" on page Z-68).
wstrohm is offline  
Reply With Quote
Old 07-10-10, 04:20 AM
  #7
?????????????
10 Year Member
 
EFS.O's Avatar
 
Join Date: Sep 2003
Location: Greece
Posts: 511
Thanks: 0
Thanked 0 Times in 0 Posts
Originally Posted by wstrohm View Post
The RX-7 has an "Electrical Load Unit" which is located close to the PCME. Its wiring is shown on page Z-30 of the 1994 workshop manual. It receives inputs from the instrument cluster, combination switch, heater control unit (fan switch), and CPU No. 1, and outputs a signal to the PCME on its terminal N to the PCME's terminal 3B. The ELU is supposed to let the PCME know the number of electrical loads engaged so the PCME can adjust the idle to compensate. On our '94, idle speed when warm with A/C off is 720 rpm, but when A/C compressor is engaged, it jumps up to 1000 rpm. There is an A/C sensor inside the Heater Control unit (see pages Z-68 ("Ga") and Z-70 ("Gb") for the circuits that affect the input to the Electrical Load Unit on the orange/blue wire that runs through connector X-15 (circled "27" on page Z-68).

Do you have any idea why my ELU is shown always on on the pfc commander screen?

Everything is working perfect(a/c sensor cpu no.1 etc).
EFS.O is offline  
Reply With Quote
Old 07-12-10, 03:14 PM
  #8
Recovering Miataholic
 
wstrohm's Avatar
 
Join Date: Mar 2002
Location: Fountain Valley, CA
Posts: 1,423
Thanks: 0
Thanked 0 Times in 0 Posts
Do you have any idea why my ELU is shown always on on the pfc commander screen?
No, I don't know. By "on," I guess you mean that the signal to the PCME is always low? According to the "Control System" table on factory manual page F-158, the following should be true:

With headlight switch in position I or II, OR with blower motor switch in position III or IV, OR with rear defroster switch ON, the input to PCME terminal 3B should be at a LOW state. If all those units are OFF, the signal at 3B should be a HIGH.

If you have a PFC, I have no idea how the engine should react, but at least the ELU should behave as described at its terminal N.
wstrohm is offline  
Reply With Quote
 
 
Reply

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
jsesq
3rd Generation Specific (1993-2002)
27
09-25-15 11:10 AM
gxl90rx7
Haltech Forum
4
09-14-15 03:09 PM
AXA
Single Turbo RX-7's
8
09-05-15 10:06 AM
rx7shirley
2nd Generation Specific (1986-1992)
6
09-02-15 02:11 PM


Thread Tools
Search this Thread
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 07:55 PM.


All content Copyright 2007 by Internet Brands, Inc.