Honda D Series Forum banner

1 - 10 of 10 Posts

·
Registered
1999 Civic D16Y7 5M/T
Joined
·
3 Posts
Discussion Starter · #1 ·
Hey! New to the forum! I have searched and searched and now I could use some help

Im having an issue with my condenser fan and ac clutch not kicking on when I turn my ac on. And this is what ive come up with so far....

The green ac light DOES come on when I attempt to use my ac.

*Both fuses, the 7.5 under the dash and 20 under the hood are good.
* both the compressor and conderser fan relays work (swapped them both with cooling fan relay to make sure)
*I can jump both conderser fan and compressor from under the hood
  • at the pressure switch, blue/red read 4.5v and red and white read 14.1v
  • pin A17 while unplugged with car on will NOT engage clutch when grounded and when backprobed reads 14.1v while plugged in
*YES the a/c pressures are correct.

Is there anything else im missing? And given this info what conclusion do you come to? I dont have access to a known good ecu to test. And the civics at the yards here no longer have their ecus. ANY help would be greatly appreciated!

Thank you in advance!
 

·
Registered
Joined
·
6,645 Posts
what did you test the system pressure with?

Did the system work if you jump the switch?

Does the compressor clutch actually engage when power is applied and engine is running?

Has the drier ever been changed?
 

·
Registered
93 Civic HB SI
Joined
·
1,107 Posts
Do you have 12V present at the relay legs that actually provide power to the compressor clutch or condenser fan? If not, then those relays can try to click on as much as they want but will not forward power to the component.

Checked for presence of ground at the component plugs?

If you think the system has a charge, and 12V is present at the clutch and condenser fan relay legs, I would manually try engaging them by using a jumper wire across the two terminals that provide power to the clutch and fan, simply to prove that the fan could come on and that the clutch and compressor could actually run by providing power manually at the fuse block.

If those components run from the fuse block, wiring from there all the way to the components is good, and now you need to figure out if the climate control is even trying to turn the relays on at all. A test light at the fuse block, engine running, AC switch on, are your friends here. Verify the control/coil legs of the relays in question are even trying to be commanded on. If not, you need to figure out why.
 

·
Registered
1999 Civic D16Y7 5M/T
Joined
·
3 Posts
Discussion Starter · #4 ·
Yes, the system worked originally, I used a manifold gauge set to charge the and check the a/c system. I have all 14.1v to the fuse block under the hood to both the condenser and compressor relays, in fact, I jumped both relays at the same time and was able to get cold air out of the vents. The drier has NOT been changed. I can manually get the ac to come on using 2 jumpers.
 

·
Registered
93 Civic HB SI
Joined
·
1,107 Posts
Ok if the compressor and condenser fans work normally when jumped, then you have to start interrogating those relay controls.

The HVAC control head ultimately controls those, but it uses additional sensors and inputs from other components to know how and when it is appropriate to turn the AC on... you need to make sure the control head inputs are present at the control head, and that their signals are VALID.

If so, then you need to see if the HVAC control head is trying to actually to turn those relays on to engage AC.

If it is, then you could have a wiring issue between the control head and the relays.

Else, an HVAC control head issue or some kind of input to the ECU is satisfying the AC inhibit condition, so the control head wont allow AC operation for some reason.

Everything can be chalked up to an if/else based action/reaction....
 

·
Registered
Joined
·
6,645 Posts
If jumping the relay terminal made it blow cold air, then you are simply left with figuring out whether it is a simple wire problem, or if the AC module is bad.

What did you mean by ecu anyways? if talking about the engine PCM/computer, that does not turn the AC on or off. It simply can sense if AC is turned on, so that the idle is turned up a few hundred RPM's when idling.

here is a decent video on showing the components. I would first check the wiring harness at the big 4pin plug. If you can, unplug it, stick a multimeter pins in there, and start wiggling lines to see if something is barely conencted
 

·
Registered
'91 CRX DX, D15B (D15Z7), DX L3
Joined
·
87 Posts
if talking about the engine PCM/computer, that does not turn the AC on or off. It simply can sense if AC is turned on, so that the idle is turned up a few hundred RPM's when idling.
The ECU does actually intercept the A/C switch signal. I suspect it normally delays activation of the compressor clutch slightly to make sure the idle boost syncs up with the drag from the compressor. Shutting off the compressor when the idle is too low would also make sense. There is (or at least was at one point) aftermarket ECU firmware that disables the A/C compressor above a certain throttle percentage to maximize available power.
 

·
Registered
Joined
·
6,645 Posts
You are correct. I forgot about how the ecu can control the AC relay to turn it off at higher engine rpm and on newer mdoels, when the coolant temp is too high
 

·
Registered
Joined
·
36 Posts
Have you run through the troubleshooting steps in the service manual? This is sure to diagnose your issue, as it did mine, when I had an open in a pinched wire at the compressor that led to intermittent A/C.
 

·
Registered
1999 Civic D16Y7 5M/T
Joined
·
3 Posts
Discussion Starter · #10 ·
Ok, problem solved, it turned out to be a bent pin on the thermostat connector behind the glovebox, a/c is ice cold. Thank you all for the ideas! It didnt go unnoticed!
 
1 - 10 of 10 Posts
Top