A/C control relay modification
05-01-2006, 10:37 PM
#1
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Thread Starter
A/C control relay modification
Well I had been reading about the under-sized relay in the A/C control head of my 84S. I decided that I would use a couple of extra relays that I had. I mounted them near the jump post. I found the A/C compressor clutch wire just above the PS timing belt cover, cut the wire and used it to control the new relays. One relay turns on the clutch powered from a fused connection to the jump post. The other relay grounds the refrigerant temp. switch connection above the receiver-drier(switch is disconnected). Grounding this activates the factory auxilliary fan relay thus turning on the pusher fan in front of the condenser/radiator.
Results:
Each time I turn on A/C, the control head only has to switch milliamps rather than amps and the Aux. cooling fan turns on too. I'm using R134 so I think this will help keep temps and pressures down a little.
One factory wire was cut and soldered, one refrig. switch disconnected.
I think this combines one of Wally's suggestions about fan control with a fix of a common weakness in our A/C control head. It took about an hour. If I can figure out how I'll post a diagram if anyone wants.
Dave McK.
Results:
Each time I turn on A/C, the control head only has to switch milliamps rather than amps and the Aux. cooling fan turns on too. I'm using R134 so I think this will help keep temps and pressures down a little.
One factory wire was cut and soldered, one refrig. switch disconnected.
I think this combines one of Wally's suggestions about fan control with a fix of a common weakness in our A/C control head. It took about an hour. If I can figure out how I'll post a diagram if anyone wants.
Dave McK.
05-02-2006, 06:55 PM
#4
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Yep ...Me too. Although simple in strategy, an actual schematic would be most helpful for those, that may be less than 12VDC circuit proficient.
Thanks...
Thanks...
05-03-2006, 02:02 PM
#6
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Thread Starter
Not able to post diagram from my scanner so I'll type it:
1.) Interrupt wire from AC control head to compressor (located near top PS timing belt cover)
2.) Disconnect refrigerant temp switch on top receiver drier. This leaves two wires available one is a ground one is from AC fan relay.
3.) Add two new generic SPST relays. Connect as follows:
RELAY I: 85 from AC control head
86 to ground
30 to 12V at jump post via 10 amp fuse
87 to AC compressor clutch
RELAY II: 85 from AC control head
86 to ground
30 to ground
87 to AC fan relay (striped wire from disconnected refrig temp sw.)
I didn't use any diodes.
I notice that the AC fan does pull some power since my voltmeter drops at idle and the fan is not silent by any means.
Good luck,
Dave McK.
1.) Interrupt wire from AC control head to compressor (located near top PS timing belt cover)
2.) Disconnect refrigerant temp switch on top receiver drier. This leaves two wires available one is a ground one is from AC fan relay.
3.) Add two new generic SPST relays. Connect as follows:
RELAY I: 85 from AC control head
86 to ground
30 to 12V at jump post via 10 amp fuse
87 to AC compressor clutch
RELAY II: 85 from AC control head
86 to ground
30 to ground
87 to AC fan relay (striped wire from disconnected refrig temp sw.)
I didn't use any diodes.
I notice that the AC fan does pull some power since my voltmeter drops at idle and the fan is not silent by any means.
Good luck,
Dave McK.
Last edited by j.kenzie@sbcglobal.net; 05-03-2006 at 02:03 PM. Reason: typo
05-03-2006, 03:41 PM
#7
Chronic Tool Dropper
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email the drawing to me in your graphic format and I'll make it a PDF so it can be downloaded. dr.bobf [at] att.net should do the trick.
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05-07-2006, 08:49 PM
#9
Rennlist Member
Thread Starter
OK
I found out why the factory didn't have the AC fan come on every time the AC comes on: The alternator/ battery can't handle it. After 5 days, the car stalled and I needed to recharge the battery.
I returned my AC fan to refrig switch control and left the compressor relay as described.
I'll see how the R134 works and I have been looking at Carl's high output alternator just in case.
FWIW,
Dave McK.
I found out why the factory didn't have the AC fan come on every time the AC comes on: The alternator/ battery can't handle it. After 5 days, the car stalled and I needed to recharge the battery.
I returned my AC fan to refrig switch control and left the compressor relay as described.
I'll see how the R134 works and I have been looking at Carl's high output alternator just in case.
FWIW,
Dave McK.
Last edited by j.kenzie@sbcglobal.net; 05-08-2006 at 09:54 AM. Reason: clarification
05-08-2006, 04:34 PM
#11
Burning Brakes
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Originally Posted by j.kenzie@sbcglobal.net
OK
I found out why the factory didn't have the AC fan come on every time the AC comes on: The alternator/ battery can't handle it. After 5 days, the car stalled and I needed to recharge the battery.
I returned my AC fan to refrig switch control and left the compressor relay as described.
I'll see how the R134 works and I have been looking at Carl's high output alternator just in case.
FWIW,
Dave McK.
I found out why the factory didn't have the AC fan come on every time the AC comes on: The alternator/ battery can't handle it. After 5 days, the car stalled and I needed to recharge the battery.
I returned my AC fan to refrig switch control and left the compressor relay as described.
I'll see how the R134 works and I have been looking at Carl's high output alternator just in case.
FWIW,
Dave McK.
05-08-2006, 04:42 PM
#12
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Thread Starter
Well I may have a reprieve. Even without the fan my voltmeter has been drifting downward from 13+ to 12 to 10+. I recharged my battery again today. Had the system checked and the alternator is putting out 65A at 2000RPM but the battery does not hold a charge. New battery ordered $$. Hopefully will fix problem. Looking back this may have been developing over some time. BTW lately my voltmeter needle goes up and down slightly with my turn signal flasher at idle.
Dave
Dave
