Hello everyone!

I have had my 94 Ranger 3.0 STX for about 9 years now and have recently revived the once dead AC system in it. When I got the Ranger, someone had removed the compressor and bypassed with shorter belt. They had cut the low and high pressure lines and put tape over the ends, for whatever reason.

So, this summer, I finally decided that I was tired of roasting in the hot SC days when going from place to place and got a used compressor from my local u-pull-it and purchased all new lines, accumulator/dryer, orifice tube, condenser and evaporator. I did try the system with just using a new accumulator, orifice tube and manifold lines, and it did work, but, the compressor would work and cool well all day long, at idle, but as soon as you went off idle, it would kick off and stop working. At this point, I went all the way, buying a vacuum pump, gauges, etc. I installed another compressor, and all of the rest of the new hardware mentioned above, drew a vacuum, let sit, verified there were no leaks, and charged the system with 7oz PAG oil and R143a

Much to my disappointment, it did the same thing. It worked awesome (especially after replacing that evap coil... The whole airbox was FULL of leaves and blew hardly anything!), as long as you were idling. But, drop her in gear, touch the gas and the compressor cuts off and won't come back on until the next day after the truck has sat for a while. I found this very weird. I checked out the wiring diagrams and found that it is possible the WOT cutout relay was having issues, so I replaced it, same problem. After this, I found some other info on various sites that mentioned jumping the two necessary pins at the relay, effectively making the compressor live all of the time, unless there was a lack of or too much pressure in the system. I added the jumper after just shutting it off, to bypass the WOT relay, and the compressor came back on and the air was VERY cold (felt great). The problem was gone with it cutting off with the slightest throttle! But, I cannot leave it this way as I would like to have it functiona normally, just cannot figure out why it is doing what it is doing! I could just simply add a switch in the cabin to bypass the WOT relay, giving me manual control, but would rather do it right if possible.

My question is, what is the most likely problem here? The TPS sensor (I have not tested it yet), the EEC? The Ranger runs good, but does have a DTC code 336 which I have not been able to figure out yet. Could it be related somehow? I have tried two other pressure feedback sensors, new vacuum lines, etc, not help. I have yet to replace the EGR valve itself though...Thoughts on that?

Can anyone help point me in the right direction? I love my Ranger, and with the longer bed, she comes in very handy and has served me well!!

Thanks everyone!

Thanks in advance everyone!

 

Welcome to the forum

WOT(wide open throttle) relay is a 5 pin relay
This relay is OFF when sending 12volts to the compressors clutch coil(AC on)
Computer activates the relay to shut compressor OFF when throttle sensor shows 4.5volt, to give the driver all engine power for passing or ??

Its a Reverse use Relay, relay off/AC on, relay on/AC off

So jumpering the relay's slot 30 to slot 87A is the normal position of the WOT relay, off, and AC on

So could be an issue with TPS(throttle position sensor), 3 wire sensor that reads throttle plate position
Put back in the WOT relay
Unplug the 3 wire connector on TPS
Start engine
See if AC cuts off when throttle is used

If not then replace TPS and check its wires, its a 5volt sensor, 5v wire, ground wire, and a signal wire, under 1v throttle closed, 4.5v at WOT
Works like a light dimmer or volume control, its a variable resistor
If there is an internal short it may be going from 1v to 5v as soon as its moved
You can uses a needle to pierce TPS center wire, then use a volt meter(key on engine off) to see its Signal voltage back to computer
.69 to .99v throttle closed
Then a steady increase in volts as throttle is opened, WOT should be 4.5 to 4.8v

If it still cuts off then its a Computer issue
Pull out computer and open it up, see if you can see any damage, there are 3 capacitors that can leak after 20+ years and cause odd issues, under $5 to replace these and should be done regardless, if you plan on using the computer

1994 AC wiring diagram below

The pink/yellow wire from the Computer(PCM) pin 54 is what grounds the WOT relay to turn off the compressor
As is you could just cut this wire so computer could no longer activate the Cutoff, the AC system can still be turned off in the cab by the Climate Control switch
WOT Relay was a convenience addition to the system, not a requirement, to give driver more engine power when needed, at WOT