A/C Compressor clutch not getting power

[OG Gearhound]

Hello! I've tried to search this forum for info related to my problem, but I guess I'm too much a noob to figure out how to search effectively.
I have an 89 Ranger xlt, 2wd, 2.9l, 5-speed with 29k original miles. A/C clutch will not engage. The light next to the knob on the panel DOES light, so the fuse is good.. I also did check the fuse.
I am getting voltage to the low-pressure switch and did the 'jump' test on it, no clutch. I put a multi-meter on the plug at the a/c clutch and there is NO VOLTS. I traced the lead all the way to the connector before it goes into the relay box, separated it and tested for volts there coming straight from the box and there are NO VOLTS. Ground is good.
Finally, I did a DIRECT POWER jump from the battery and ground to the A/C Clutch and it runs and air blows cold.
As far as I can find, there is NO dedicated A/C Relay.
Truck runs perfectly otherwise.
Any help or direction to another thread would be most appreciated.
Thanks in advance!!

 

[Jazzer]

On my ‘87, in the fuse panel just to the left and above the round turn signal flasher, there’s a 30 amp fuse that feeds the hvac blower motor and AC clutch. Have you checked that?

-Jazzer

 

[RonD]

AC relay is called WOT(wide open throttle) relay

Diagram here for its location in 1989 Ranger: https://ww2-secure.justanswer.com/uploads/BR/brimax/2012-11-18_231834_89_ranger_fuel_pump_relay.gif

Its under the engine bay fuse box
WOT relay will have a Black base
Fuel pump relay Green base
EEC(computer) relay a Brown base

In 1989 the 12volts for the AC Clutch runs like this

Fuse----Dash AC switch-----------pressure switch------------WOT relay------------AC Clutch---ground

WOT relay is a 5 pin relay, when relay is OFF the 12v from pressure switch passes thru this relay and to the AC Clutch turning it ON

When Computer sees WOT by driver it activates the relay turning OFF AC so driver has maximum power to pass or accelerate, when driver lets off the gas pedal then AC will come back on

 

[OG Gearhound]

AC relay is called WOT(wide open throttle) relay

Diagram here for its location in 1989 Ranger: https://ww2-secure.justanswer.com/uploads/BR/brimax/2012-11-18_231834_89_ranger_fuel_pump_relay.gif

Its under the engine bay fuse box
WOT relay will have a Black base
Fuel pump relay Green base
EEC(computer) relay a Brown base

In 1989 the 12volts for the AC Clutch runs like this

Fuse----Dash AC switch-----------pressure switch------------WOT relay------------AC Clutch---ground

WOT relay is a 5 pin relay, when relay is OFF the 12v from pressure switch passes thru this relay and to the AC Clutch turning it ON

When Computer sees WOT by driver it activates the relay turning OFF AC so driver has maximum power to pass or accelerate, when driver lets off the gas pedal then AC will come back on

Aha, under the "power distribution box" that is above the passenger wheel-well in the engine compartment? Ok then. that's why I couldn't find that sucker!!
Thanks a bunch, it's dark out now, but I'll check it in the morning!

 

[OG Gearhound]

On my ‘87, in the fuse panel just to the left and above the round turn signal flasher, there’s a 30 amp fuse that feeds the hvac blower motor and AC clutch. Have you checked that?

-Jazzer

Yessir, done checked that one. I think it's the WOT relay though.
Much Appreciated!

 

[Jazzer]

You can always count on RonD.

 

[OG Gearhound]

Aha, under the "power distribution box" that is above the passenger wheel-well in the engine compartment? Ok then. that's why I couldn't find that sucker!!
Thanks a bunch, it's dark out now, but I'll check it in the morning!

Btw, my quotations weren't meant as a correction to you sir. That's just what it says in the owner's manual I read a couple hours before my post. I appreciate your help, links and especially the power flow guide to the a/c clutch.. most helpful.
Thanks again!

 

[OG Gearhound]

Udate: I just replaced the WOT relay.. did not solve the problem.
I think I'm just going to run a bypass with a toggle switch.

 

[RonD]

Do you have 12volts at the pressure switch?

Unplug it and test, with AC switch ON in the cab, one wire at the pressure switch should have 12volts
If not then that's the problem, wire from AC switch to the pressure switch

If it has 12volts then you can do a jumper from the OTHER WIRE on the pressure switch to the AC clutch, by passing the WOT relay wiring

DO NOT by pass the pressure switch, you will either burn up compressor or blowout an AC hose

 

[OG Gearhound]

Do you have 12volts at the pressure switch?

Unplug it and test, with AC switch ON in the cab, one wire at the pressure switch should have 12volts
If not then that's the problem, wire from AC switch to the pressure switch

If it has 12volts then you can do a jumper from the OTHER WIRE on the pressure switch to the AC clutch, by passing the WOT relay wiring

DO NOT by pass the pressure switch, you will either burn up compressor or blowout an AC hose

Yessir, I've done all that. 12 volts at the pressure switch. no volts at the clutch.
I thought for sure the relay would solve it, because I also tested for Voltage right there below the relay module.. there is a connector there that includes the 'hot' black w/yellow stripe wire that follows to the a/c clutch and to the relay box in the other direction.. i separated that connector and tested for voltage at side coming from the box, and nothing.
Maybe the 'made in china' relay i bought is bad?

 

[RonD]

Its a 5 pin relay correct, 4 pin relay won't work, can't pass voltage when OFF

Ford used 2 kinds of relays, mini and micro

Mini diagram here: http://www.gtsparkplugs.com/images/mini-automotive-relay-wiring-840x.jpg

Micro diagram here: http://www.gtsparkplugs.com/images/micro-automotive-relay-wiring.jpg

Relays use an odd numbering system, from the old VW days, first to use relays
85 and 86 are the Coil that activate a relay, low amp side

30 and 87 are the contacts that pass the higher amps, these are connected when relay is ON, activated

87A is the 5th pin, also high amp rated, its connected to 30 when relay is OFF, disconnected when relay is ON

Most relays are 4 pin, because that's all that is needed, no 87A, WOT relay only works if it has 87A

You can remove relay and put a jumper between 30 and 87A in relay socket(base) and should then see 12v at AC clutch

 

[OG Gearhound]

Its a 5 pin relay correct, 4 pin relay won't work, can't pass voltage when OFF

Ford used 2 kinds of relays, mini and micro

Mini diagram here: http://www.gtsparkplugs.com/images/mini-automotive-relay-wiring-840x.jpg

Micro diagram here: http://www.gtsparkplugs.com/images/micro-automotive-relay-wiring.jpg

Relays use an odd numbering system, from the old VW days, first to use relays
85 and 86 are the Coil that activate a relay, low amp side

30 and 87 are the contacts that pass the higher amps, these are connected when relay is ON, activated

87A is the 5th pin, also high amp rated, its connected to 30 when relay is OFF, disconnected when relay is ON

Most relays are 4 pin, because that's all that is needed, no 87A, WOT relay only works if it has 87A

You can remove relay and put a jumper between 30 and 87A in relay socket(base) and should then see 12v at AC clutch

Ok, mine is the Micro configuration of 5pin. I'll try the jumper at the socket and see what happens.
Thanks for the links.

 

[OG Gearhound]

Ok, mine is the Micro configuration of 5pin. I'll try the jumper at the socket and see what happens.
Thanks for the links.

Udate: I just performed the jump and NO volts.. I also tested the relay using multimeter ohm and turns out to be GOOD as well as my old relay is still GOOD. so I guess there is a break in the line somewhere?

 

[RonD]

Test slot 30 and 87A for 12volts from the pressure switch, Ford could have use either for this relay setup

If no 12v on either then yes, wire from pressure switch is bad
If one does have 12v then wire from relay socket to AC clutch is bad



And just heads up on testing voltage on wires
Test battery volts FIRST, say its 12.5volts, key off
Then test it key ON, engine off, say its 12.4v

When you test wires you should see EXACTLY the same volts as key off or on, depending on what you are testing, but no less
If key on wire test showed 12.1volts, that's a 0.3v drop, so there is a problem on that wire

A volt meter draws very very little amps, where a device draws alot of amps
So a 0.3v drop with meter test could be a 3 to 5volt drop with device connected, usually corroded connector or wire issue

 

[Paulos]

You should have 12 volts when checking between a good ground and both/either wires at the pressure switch if the switch is working correctly. It's a switch, so 12v+ in and 12v+ out when the system has sufficient pressure. Unless the contacts are actually burned out (unlikely) in the WOT relay, it will have nothing to do with the AC not working, as it is a normally closed relay.