wot ac relay wiring - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 15 Old 11-05-2017, 09:05 PM Thread Starter
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wot ac relay wiring

1987 gt, ac pump wont turn on. i have power to all components on the the passenger side of car. when i bridge the wot relay the pump turns on. any idea what could be my problem?

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post #2 of 15 Old 11-06-2017, 01:58 PM
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Check for power to the coil

The ecm controls that relay


89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #3 of 15 Old 11-06-2017, 03:06 PM
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If I am not mistaken, the clutch on most AC compressors will not engage if it is low on refrigerant either. The refrigerant is the lubricant, so they don't want the compressor running without it. There is a pressure switch in the circuit as well. I am by know means an expert, just saying in my experience refilling, the compressor never comes on until a few cans are installed.
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post #4 of 15 Old 11-06-2017, 05:07 PM Thread Starter
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I put 2 1/2 cans in the system. when i bridge the relay it runs cold. Indy,which coil are you referring to?
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post #5 of 15 Old 11-06-2017, 09:17 PM
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Quote:
Originally Posted by pabloairmale View Post
I put 2 1/2 cans in the system. when i bridge the relay it runs cold. Indy,which coil are you referring to?
the coil of the relay you jumped

how much refrig you put in the system means nothing

you use a voltmeter to test a switch.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #6 of 15 Old 11-06-2017, 09:19 PM
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Quote:
Originally Posted by MadViking View Post
If I am not mistaken, the clutch on most AC compressors will not engage if it is low on refrigerant either. The refrigerant is the lubricant, so they don't want the compressor running without it. There is a pressure switch in the circuit as well. I am by know means an expert, just saying in my experience refilling, the compressor never comes on until a few cans are installed.
the refrigerant is NOT the lubricant

the pressure switch is there to prevent the evap from freezing.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #7 of 15 Old 11-07-2017, 08:55 AM Thread Starter
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the relay has power on 2 of the 4 wires, power from the pressure switch, power in from a red cable. the orange cable from the ecm has nothing and the black and green cable that goes to the ac pump has nothing. going to check the ecm pin and make sure its connected then recheck the pressure in the system. i replaced the pressure switch with a r12 switch, but going to look into a r134 switch. rock auto has a different part number. i noticed that the relay also has 2 part numbers, one is $9 and the other is $28. do you know if thats a special relay or just a regular relay?
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post #8 of 15 Old 11-07-2017, 09:45 AM
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why are you changing parts?

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #9 of 15 Old 11-07-2017, 11:58 AM Thread Starter
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not sure if the switch needs to be a different pressure rating for the 134a to work in the system.
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post #10 of 15 Old 11-07-2017, 07:11 PM
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can be adjusted with gauges hooked up, and turning the adjustment screw, under the plug


89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #11 of 15 Old 11-15-2017, 12:51 PM Thread Starter
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did a maf coversion on this car a while back and wondering if the ecc orange wire on the wot relay is in the same position(pin 54) for a years. found 88 thru 93, cant find 87
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post #12 of 15 Old 11-15-2017, 03:42 PM
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Test the pin with test light to batt pos

Turn on a/c and snap to wot
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post #13 of 15 Old 11-15-2017, 06:12 PM Thread Starter
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pin iam asking about is the orange wire which grounds the relay. just need to now what position it is on a 87 car. thanks
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post #14 of 15 Old 11-15-2017, 07:33 PM
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like I said, use a test light to confirm,

battery positive now, when the ecm grounds it, the light will come on

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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post #15 of 15 Old 11-17-2017, 10:52 AM
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Quote:
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did a maf coversion on this car a while back and wondering if the ecc orange wire on the wot relay is in the same position(pin 54) for a years. found 88 thru 93, cant find 87
Orange/Light Blue
Probably can't see the blue, anymore.
The ECU grounds this.
It should be the same for '87, pin 54. ECU for both was the same Speed Density. Calif was MAF for '88.
You can test the relay without turning the engine on.
Turn ignition ON, Turn the AC on & off. You can now hear the compressor clutch engage & disengage.
Remove the connector & substitute a test light.
Sounds like the relay coil is bad.
Disconnect the relay from the connector, put ohmmeter across where Red & Orange Lt Blue were, should read 100-200 ohms, not infinity.
The relay is "special" because it mates to the Ford connector & has an attached mounting bracket.
If the cheaper one plug in to the factory connector, you probably can use that.
Give us pics.
I just got my Megasquirt ECU wired to perform this function.
The connector insulation to this relay was in bad shape on one wire, was able to tape it up. First time it was removed in 30 years.


UPDATE:
Found the 2 relays on Rock Auto. $16.07 & $20.89

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1988 GT, 57k mi, Orig Owner
ProCharger P600B, FRPP Headers, Flowmaster F2, 3G Alt, Mk8 Fan/DCC, 3.55's, Prog Springs, ST Brace, G/Trac Bar, Subfrms, UCA, LCA, FCA, Tokico 5-ways, C/C Plates, CSA 16x8, Bridgestone RE760 Sport 225/50R16, Megasquirt DIYPNPF60, LC2 WBO2, C&L76mm MAF w/LU47's
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