96 explorer a/c electrical question

[IanL]

Hello All
It has been some time since you assisted me so I hope I am not posting and old question.
History
2 years ago I replaced all components of my ac system with the exception of fuses and relays.
system ran fine and registered 58 degrees at the register. ran vehicle for a complete summer season then retired it( We bought a expedition).
I just resurrected it and the ac clutch does not engage.

What I have done so far
1 Disconnected low pressure sw and clutch connector
2 shorted low pressure sw connector
3 started engine and turned on dash controls requesting max ac ( ac light turns on and blower fan energizes )
4 performed bench test on wot relay and it works fine
5 wot relay engages when plugged in

What I found with a volt meter
1 0 volts at clutch connector
2 with a pulled wot relay, 13v @relay socket pin 86 relay coil
3 3.6v @ pin 30

shouldnt there be 13v at pin 30 of the wot relay the common?
Also, there appears to be no connector lug or wire for wot relay pin 87 in the socket

 

[gmanpaint]

If you have voltage coming into the pressure switch, but none coming out, the switch is bad. Test light is all you need for that test.

If you have no voltage going into the pressure switch, check the fuse.

You can also jump the clutch on the compressor to test if it works or not. Unplug it, ground it, and use a jump wire from the battery for a second. It should turn on instantly.

So there is two tests for you to try for free.

If the refrigerant is too low, the pressure switch won't activate the clutch. It needs a certain amount of pressure to work. Chances are, it's just out of juice after sitting.

 

[IanL]

If you have voltage coming into the pressure switch, but none coming out, the switch is bad. Test light is all you need for that test.

If you have no voltage going into the pressure switch, check the fuse.

You can also jump the clutch on the compressor to test if it works or not. Unplug it, ground it, and use a jump wire from the battery for a second. It should turn on instantly.

So there is two tests for you to try for free.

If the refrigerant is too low, the pressure switch won't activate the clutch. It needs a certain amount of pressure to work. Chances are, it's just out of juice after sitting.

As I said i my post
Low pressure switch is out of the equation and the connector jumped therefor the system thinks the pressure switch is fine and with the connector bridged should allow compressor to cycle with or without freon. ( Just like it does on a recharge when you force the compressor to cycle in order to add new freon) .
And yes I could bump the compressor clutch directly from the battery. And if it fires, what then? I still would not know where the problem is.
All fuses are fine. ( #18 in Dash Fuse Box) cant see any others identified directly with ac
I am an old school EE and used to developing P&ID's and electrical loop diagrams for the Nuclear industry. Even though I have been retired for over 20 years I still understand logic and can read a schematic and a wiring diagram. If you could steer me to a good schematic and wiring diagram I could develop a loop diagram and post it for others.
For those following this post who do not know what a loop diagram is.

A loop diagram is a drawing that reflects all interconnections, their location, wiring color code, voltages present either normal or fail safe, with regards to a specific device. It shows only components associated with the device in question. In other words you don't need to read schematics for an entire car in order to extrapolate lights, radio, security wiring etc to facilitate diagnosis of a problem.

 

[410Fortune]

This is the 96 4.0 correct?
Have you tried jumpering the high pressure switch too?
both high and low pressure switches must be "working" for the compressor to kick on, jump the low side and high side switches see if the compressor runs

 

[Gary Crist]

Is this what you are looking for?
This was lifted from a thread about 4 pages back....

"The Mystery Machine"

 

[IanL]

Is this what you are looking for?
This was lifted from a thread about 4 pages back....

View attachment 318089




"The Mystery Machine"

Thank you, this is exactly what I was looking for. However, even this is somewhat confusing. The note by the compressor clutch concerning the wot relay states that when de energized, power is permitted to the clutch solenoid via wot relay pin 30 and 87a. This cant be true as pin 30 is the common, and 87a is a normally open contact, and 87 is the normally closed contact. This configuration is actually embossed on the relay housing. A de energized relay would effectively create an open circuit to the compressor clutch solenoid. All in all, with this diagram I should be able to determine where the 12 volts is being interrupted. I wonder if this manual is a factory repair or Hayes, or what?

 

[IanL]

Thank you, this is exactly what I was looking for. However, even this is somewhat confusing. The note by the compressor clutch concerning the wot relay states that when de energized, power is permitted to the clutch solenoid via wot relay pin 30 and 87a. This cant be true as pin 30 is the common, and 87a is a normally open contact, and 87 is the normally closed contact. This configuration is actually embossed on the relay housing. A de energized relay would effectively create an open circuit to the compressor clutch solenoid. All in all, with this diagram I should be able to determine where the 12 volts is being interrupted. I wonder if this manual is a factory repair or Hayes, or what?

I used this diagram and this is what I have determined so far.
1. Fuse 18 is good as all interior ac fans work
2. There is 12 volts at the High Pressure Switch ( Both contacts, indicating sw is ok
3. zero volts at low pressure sw
4. wot relay energized
5. 12 volts not present at wot relay pin#30 the common ( Why the damn thing will not work )
6. One diagram shows a 10 amp fuse feeding pin 30 of the wot relay but does not indicate fuse location

 

[koda2000]

Are you sure you're not just low on refrigerant?

 

[IanL]

Are you sure you're not just low on refrigerant?

That was the first thing that I thought of and checked.
However, 12 volts should be available at the wot relay pin 30 as a permissive to the clutch solenoid vie the low pressure sw closed contacts and the high pressure sw contacts. If both of these contacts are shorted at the connector, and the wot relay is energized, you should read 12 volts at the clutch solenoid connector even if the system is totally empty.
If I understand the system logic correctly
1. turn on ignition and start engine
2. Request max ac from all internal controls, both front dash and rear.
3. If all fans turn on, blow air out of the registers, and ac light turns on, then pcm module has requested wot relay to energize
4. If Wot is energized then 12 volts should be available at wot relay contacts #30 and # 87e
5. Wot relay contact 87e supplies 12 volts to low pressure sw and compressor clutch solenoid.
6. The dash temp control either requests a continuous 12volts (max) or cycled 12 volts based on temp setting to the wot relay contacts.

After verbalizing the logic it would appear my problem may be in the dash controls, and that is where my 12 volts is interrupted.

 

[koda2000]

If you have the EATC HVAC controls, there is a small relay inside the EATC module that controls the compressor clutch. I recall multiple instances where this relay has broken it's solder joints to the circuit board it's attached to. Re-soldering the relay to the board has fixed the issue for others. IDK if the power flows through the WOT relay on it's way to the compressor though.

 

[IanL]

If you have the EATC HVAC controls, there is a small relay inside the EATC module that controls the compressor clutch. I recall multiple instances where this relay has broken it's solder joints to the circuit board it's attached to. Re-soldering the relay to the board has fixed the issue for others. IDK if the power flows through the WOT relay on it's way to the compressor though.

Thank You
Is that relay in the dash as part of the onboard ac controls, or in the engine compartment,
ps All ac compressor clutch solenoid power must pass through the wot relay. This is how the ac is automatically cutoff when driving in hilly terrain and or long incline grades in order to reduce engine load.

 

[koda2000]

Thank You
Is that relay in the dash as part of the onboard ac controls, or in the engine compartment,
ps All ac compressor clutch solenoid power must pass through the wot relay. This is how the ac is automatically cutoff when driving in hilly terrain and or long incline grades in order to reduce engine load.

The relay is located inside the EATC module itself on it's circuit board. You have to remove the EATC unit (4 screws once the radio bezel is removed), small vacuum line manifold and electrical connections. Take the module apart and once the board is exposed the relay is a small black plastic square on the board. Someone had posted a pic of the board and relay in the past. You can try searching for it using the forum's search feature (which doesn't work very well), but you may have better luck using Google search. Once you ID the relay check the bottom of the board for signs of cracks/breaks on the relay's solder joints and re-solder them. I suppose it would be possible to also test the relay's output with a VOM

I wouldn't say that this is a common issue, but it's been reported here multiple times. There's a member named @J_C who seems to be one of our more knowledgeable members on electrical issues. Maybe he could be of help with this, IDK. You could try PM'ing him, or perhaps he'll read this post.

I found this thread, but no photo's and supplied link by @bobflood didn't work. You may find it interesting though.

AC Compressor gets no signal from EATC

Hello, I am new to this site, and being reading many threads. There is a ton of information here and the best is, it is specific, but I am still not sure how to resolve this issue. So I decided to post in the hopes a member can help me. I have a '97 Ex EB 4.0L and my AC compressor is not...

www.explorerforum.com

 

[IanL]

The relay is located inside the EATC module itself on it's circuit board. You have to remove the EATC unit (4 screws once the radio bezel is removed), small vacuum line manifold and electrical connections. Take the module apart and once the board is exposed the relay is a small black plastic square on the board. Someone had posted a pic of the board and relay in the past. You can try searching for it using the forum's search feature (which doesn't work very well), but you may have better luck using Google search. Once you ID the relay check the bottom of the board for signs of cracks/breaks on the relay's solder joints and re-solder them. I suppose it would be possible to also test the relay's output with a VOM

I wouldn't say that this is a common issue, but it's been reported here multiple times. There's a member named @J_C who seems to be one of our more knowledgeable members on electrical issues. Maybe he could be of help with this, IDK. You could try PM'ing him, or perhaps he'll read this post.

I found this thread, but no photo's and supplied link by @bobflood didn't work. You may find it interesting though.

AC Compressor gets no signal from EATC

Hello, I am new to this site, and being reading many threads. There is a ton of information here and the best is, it is specific, but I am still not sure how to resolve this issue. So I decided to post in the hopes a member can help me. I have a '97 Ex EB 4.0L and my AC compressor is not...

www.explorerforum.com

Thanks for the help
Will check out the circuit board. If the board is wonky I will apply 12 volts directly to wot relay pin 30 via a inline 10 amp fuse and see if I read 12 volts in all of the appropriate places. If the system wakes up I am good to go. I am a typical Californian in hot weather, I turn the ac to max , and if it gets too cold I back off the fan a notch or too. That way the the fuse protects the circuit and the WOT relay protects the car.

 

[koda2000]

Thanks for the help
Will check out the circuit board. If the board is wonky I will apply 12 volts directly to wot relay pin 30 via a inline 10 amp fuse and see if I read 12 volts in all of the appropriate places. If the system wakes up I am good to go. I am a typical Californian in hot weather, I turn the ac to max , and if it gets too cold I back off the fan a notch or too. That way the the fuse protects the circuit and the WOT relay protects the car.

Yeah, that might get your compressor to engage, but you also need it to cycle ON/OFF and not run continuously. I would think cycling would be controlled by the high pressure switch. As long as the compressor cycles I'd say that's good enough for now.

 

[J_C]

I'm playing catch up on this topic but will note a few things as I see them...

1) You wrote " 5 wot relay engages when plugged in". This does not appear to be the correct operation. That relay should only engage at WOT. I would leave the relay out and jumper between relay pins 30 and 87A to see if the clutch then works.

2) " 2 with a pulled wot relay, 13v @relay socket pin 86 relay coil". This doesn't seem right but I don't know what to make of it. Seems like the PCM should be closing the connection to ground to trigger the coil at WOT, and when not energized, at most some phantom voltage. *I could be wrong*.

3) "3 3.6v @ pin 30". This is definitely wrong, should be up around 14V. It makes me think one of your switches is bad or the wiring has a short somewhere. However, you should have still had that 3.6V at the clutch connector so it seems like either the clutch is pulling that down to nothing (if clutch is still plugged in), OR that WOT relay is energizing when it shouldn't.

4) However something is strange. That diagram in a prior post, appears to indicate that the relay is normally closed circuit, while the diagram I have for the manual A/C, shows it as normally open circuit, has to be energized through the PCM to turn the clutch on. I've attached that manual A/C diagram below, but unfortunately I don't have the EATC version of this in the better diagram format.

You did note something similar in your later post #6 but the question is which of these diagrams is correct and is the relay energizing when it shouldn't? It is not up to me to dictate it, but if I had designed it, then if the relay failed it would still keep A/C on at WOT, rather than fail to work at all, that it would have been a normally closed relay circuit.... but nobody asked me at the time, lol.

5) There does not need to be a connection for the WOT relay pin 87, it is not used.

6) Quote " 6. One diagram shows a 10 amp fuse feeding pin 30 of the wot relay but does not indicate fuse location" My attached diagram shows it as fuse #1 in the under-hood power distribution box, but I don't know if it is the same for a '96 4.0L.

7) Quote " 5. Wot relay contact 87a supplies 12 volts to low pressure sw and compressor clutch solenoid. ". I'm not seeing this on either diagram. It only supplies 12V to the compressor clutch, the switches are upstream of it.

Ultimately you are on the right track, tracing and measuring voltage. I would have jumpered between the WOT pins 30 and 87a to see if the clutch engaged, OR measured for resistance between these two pins, trying to determine whether this relay is supposed to be open or closed when power is flowing through it.

Yes the cycling is controlled by the switches and you can jumper out the WOT relay as a test and only lose having it disable the clutch at WOT.

There is a download to a Service Manual DVD below which might provide more information. I'll attach what I have but there is more info in it.

1996-2001 ford explorer / mountaineer workshop manual (5567 pages!)

In case any of you ever tried to find proper manual to fix your car, here's one - 1996-2001 ford explorer / mountaineer workshop manual - 5567 pages Warning: Loading of the file can take REALLY long due to the massive amount of pages in it. I hope the link works (if not i'll try find...

www.explorerforum.com

 

[IanL]

I'm playing catch up on this topic but will note a few things as I see them...

1) You wrote " 5 wot relay engages when plugged in". This does not appear to be the correct operation. That relay should only engage at WOT. I would leave the relay out and jumper between relay pins 30 and 87A to see if the clutch then works.

2) " 2 with a pulled wot relay, 13v @relay socket pin 86 relay coil". This doesn't seem right but I don't know what to make of it. Seems like the PCM should be closing the connection to ground to trigger the coil at WOT, and when not energized, at most some phantom voltage. *I could be wrong*.

3) "3 3.6v @ pin 30". This is definitely wrong, should be up around 14V. It makes me think one of your switches is bad or the wiring has a short somewhere. However, you should have still had that 3.6V at the clutch connector so it seems like either the clutch is pulling that down to nothing (if clutch is still plugged in), OR that WOT relay is energizing when it shouldn't.

4) However something is strange. That diagram in a prior post, appears to indicate that the relay is normally closed circuit, while the diagram I have for the manual A/C, shows it as normally open circuit, has to be energized through the PCM to turn the clutch on. I've attached that manual A/C diagram below, but unfortunately I don't have the EATC version of this in the better diagram format.

You did note something similar in your later post #6 but the question is which of these diagrams is correct and is the relay energizing when it shouldn't? It is not up to me to dictate it, but if I had designed it, then if the relay failed it would still keep A/C on at WOT, rather than fail to work at all, that it would have been a normally closed relay circuit.... but nobody asked me at the time, lol.

5) There does not need to be a connection for the WOT relay pin 87, it is not used.

6) Quote " 6. One diagram shows a 10 amp fuse feeding pin 30 of the wot relay but does not indicate fuse location" My attached diagram shows it as fuse #1 in the under-hood power distribution box, but I don't know if it is the same for a '96 4.0L.

7) Quote " 5. Wot relay contact 87a supplies 12 volts to low pressure sw and compressor clutch solenoid. ". I'm not seeing this on either diagram. It only supplies 12V to the compressor clutch, the switches are upstream of it.

Ultimately you are on the right track, tracing and measuring voltage. I would have jumpered between the WOT pins 30 and 87a to see if the clutch engaged, OR measured for resistance between these two pins, trying to determine whether this relay is supposed to be open or closed when power is flowing through it.

Yes the cycling is controlled by the switches and you can jumper out the WOT relay as a test and only lose having it disable the clutch at WOT.

There is a download to a Service Manual DVD below which might provide more information. I'll attach what I have but there is more info in it.

1996-2001 ford explorer / mountaineer workshop manual (5567 pages!)

In case any of you ever tried to find proper manual to fix your car, here's one - 1996-2001 ford explorer / mountaineer workshop manual - 5567 pages Warning: Loading of the file can take REALLY long due to the massive amount of pages in it. I hope the link works (if not i'll try find...

www.explorerforum.com

Thank you for the response
I think part of the problem is which is the correct wiring diagram.
If I were to use the one submitted by Gary then you would have to agree that
1. The only path for current flow to engage clutch solenoid is through the wot relay.
2. As pin 30 is the common and pin 87e is a normally open contact ( This shown on relay housing de energized )
3. The wot relay would have to be energized in order to supply current to clutch solenoid
4. The wot relay will only energize on a request of the pcm
5. The pcm request I.E. 12 volts, is supplied to the wot relay coil when ignition is on and or engine is running.
6. The 12 volts to the wot relay contacts is supplied from the EATC module via the low pressure switch , the high pressure switch, the clutch cycling eatc relay.
7. All of the above contacts are in series with each other.
8. The wot relay failsafe mode is de energized with ignition off ( You would not want a compressor clutch engaged with engine or ignition off )

Let me know your thoughts on this, I look forward to reviewing your attachments.

I am still of the opinion that it may be the eatc module at fault. It is the common denominator for 0 volts at low pressure switch, and a bogus 3.6 volts at wot relay pin 30. Remember I had all connectors disconnected when measuring voltages, so the clutch coil could not have been pulling the voltage down to 3.6v

 

[J_C]

After further review I think you are correct that the WOT relay has to be normally open on 87a since this is an always hot feed from the power distribution box, so yes you should always get ~12V on relay pin 30 then activating the relay (coil) will be necessary to power the clutch.

If the EATC is to blame that could cause lack of 12V on the pressure switch in series after it but that 3.6V reading at the relay pin 30 seems odd, I would check voltage before each switch in case one has developed some resistance that is dropping voltage.

 

[koda2000]

After further review I think you are correct that the WOT relay has to be normally open on 87a since this is an always hot feed from the power distribution box, so yes you should always get ~12V on relay pin 30 then activating the relay (coil) will be necessary to power the clutch.

If the EATC is to blame that could cause lack of 12V on the pressure switch in series after it but that 3.6V reading at the relay pin 30 seems odd, I would check voltage before each switch in case one has developed some resistance that is dropping voltage.

Is it possible that the PCM generates the 3.6V as a reference signal? I recently watched a SMA YouTube video recently where this was happening on a vehicle where there was a 12V open circuit due to bad wire. This was on a newer vehicle though. IDK that the PCM on the Gen II Explorer's is involved with A/C compressor operation.

 

[410Fortune]

Yes the PCM controls the AC compressor clutch in the Gen II explorer.

Real PITA when you try to convert Rangers to use our AC system because in a Ranger the dash controls the AC clutch...silly Ford

 

[J_C]

I doubt it's a reference signal, looks more like simple switching of the power supply, made less simple because they don't supply ALL the schematics (like the EATC internal circuit) nor follow conventional schematic symbols and design, nor give adequate descriptions of operation... and the tiny size doesn't help either, except that back in the mid-'90s that was all (an affordable) computer monitor could handle.