Hi, I have a 1986 Ford E 150 cargo van. The A/C Max setting does not work. Any ideas what and where I can check to solve the problem. I was thinking of wiring the motor to full 12v and connect a toggle switch.
Also, no air comes out of the A/C vent on the passenger side.

 

When you say "The A/C Max setting does not work", are you talking about the blower fan motor does not work on high speed?

I may be confused because you said " I was thinking of wiring the motor to full 12v and connect a toggle switch".

Or are you saying that the blower fan does not work on any speed when you have the AC selector lever set to the max position?

I will check my manual but I believe when you put the selector lever in the max position, that only operates a vacuum motor that closes the outside fresh air vent and causes the system to recirculate the cabin air. In the normal position, the vacuum motor opens the fresh air vent allowing fresh air from outside to be mixed with the air coming out the vents. When in the max position, the blower fan normally sounds louder because of the way the vents recirculate.

 

You should be able to look under the dash on the passenger side and see the cover for the heater AC box. Towards the right side you should see a screen. If you look inside you should be able to see the fresh air vent door. If you move the selector handle from Max to normal the door should open and close.

This pic is an 85




this pic is of an 88

 

I am saying that the fan works on low med high. I replaced the fan some time ago and also the fan speed control. But The selector on the dash has a normal setting and a max setting. So if the selector is on normal setting you can use it on low med or high. If it is on the max setting it should have a bit more air flow that the high setting. But when I place the selector on max it makes no difference. If the selector is on normal and med speed, I move the selector to the max setting, nothing happens, it is still on med speed. I don't think it should do that. It should blow a bit more than the high speed setting.
I read somewhere on this forum that the speed control has 3 resistors controlling the low med and high speeds. When on max setting the fan is getting the full 12 volts.

 

Ford selects different points on that resistive voltage divider network for grounds. Your fan already has connection to 12v, a direct ground connection provides maximum speed. Your resistor block may be defective.

 

Sorry for asking again but I want to make sure..

First do you have 2 different fan switches? I ask because with some dealer added AC systems, they add a second blower for the AC. Factory installed AC will only have one fan speed switch that is excluding the rear ac if you have one.

So let me get this straight,, the blower motor runs on low, medium low, medium high, and high when the selector is in the normal AC, vent, or heat position.

When the selector is on the AC max setting does the blower fan work on low, medium,and high? If I am understanding you correctly, it does.

If the fan works on all 4 speeds regardless of what position the AC max/normal, vent, heat, and defrost is in, then the problem is not in the fan electrical circuit.

You said "If the selector is on normal and med speed, I move the selector to the max setting, nothing happens, it is still on med speed. I don't think it should do that."

The fan speed will not change by moving the vent selector lever from normal to Max. The fan speed will only change when you move the fan speed selector.

The function selector lever feeds 12 volts to the blower but it starts in the OFF position so in the off position there is no power to the blower fan. In any other position then OFF, the selector lever is sending 12 volts to the blower motor.

A 1985 ford van has a 35 amp fuse that feeds the selector lever and the power goes directly to the blower motor. On a 1988 van, the selector lever is fed by a 15 amp fuse that goes to a blower motor relay. That relay is fed from a 12 volt fused link line. Either way the selector lever switches the 12 volts on or off to the blower motor, it has nothing to do with the speed of the blower motor.

JeffreyClay is correct, Ford switches the grounds for the blower motor speed.
On the 85 and the 88 vans, the blower motor speed selector switch is completely separate from the function selector lever. It sole purpose is to ground the correct terminal on the blower motor resistor and that determines the speed of the motor.

SO the blower motor does not change speed when going from normal to max ac.
If the blower motor operates on one speed, regardless of where the selector lever is, then the function selector circuit is working properly providing 12 volts to the blower motor.

If the selector lever is operating properly and the blower speed switch will operate in all 4 speeds in any one of the settings you have on the function lever happens to be in, then it will work in all of them.



What does change between normal and max ac is that the fresh air vent closes when you move the selector from normal to max.

On the post I made showing the fresh air vent,,, that is a drawing for a 1988 van. I will edit that post and also add a drawing for a 1985 van. Yours would have to be one of the two...

As to no air out the right vent.

This is for an 88





The 1985 has a end piece of duct that goes from the main duct to that vent. Perhaps it has come loose.

 

Thank you for the great diagrams annaleigh. There is only one switch. Do you think I would have to take apart the entire dash to get to the passenger vent. I think you may be right about the connection coming loose.
Okay, as far as the fan speed. I replaced the resister speed control. Everything works as far as the speeds and fan. I looked through the screen and found the stem from the vaccum was off of the door latch. I was able to put it back on and moved the switch lever from max to normal. It does move the latch back and forth but I notice no difference in the air getting colder when on the max position. I may be getting this wrong. For example, in my car, when I move the selector from normal to max the fan blower accelerates and blows the air through the vents at a much higher rate and the fan gets louder because it is running faster. So your saying that my 1985 E 150 does not work that way? When the a/c is in the max position the fan doesnt increase air flow? Then I'm wondering why there is a max setting. What is the purpose of the a/c max setting?

 

First which vent set do you have, the 88 or the 85? Second is there a 15 amp fuse or a 35 amp fuse for the blower? That will also tell us which diagram to use. you have a 1986 E150. Somewhere between 1985 and 1988 Ford redesigned the duct work and separated the AC compressor circuit from the blower motor circuit.

I think you will at least have to remove the top dash pad. I have never done it though. i believe though that you would have to remove the headlight panel (not disconnect it), the instrument panel ( not disconnecting it), and perhaps the center panel cover. Then you can access the screws holding the dash on in the front. Without going out and looking at my 88, I believe there are also some screws up at the windshield. Perhaps if someone is watching this thread, they might know for sure.

I understand what you are saying about the air blowing out with more force when the function selector is in the max position. My 02 Saturn is really noticeable when I push the recirculate button. I checked my 88 E150 today by holding a piece of paper in front of the center vent. when I moved the function selector from normal AC to max AC the air came out with more force and the fan is louder. BUT I can find nothing in the wiring diagram that would change the fan speed.
The difference in normal and MAX AC is when the function lever is in thew normal position, the fresh air vent is open allowing outside air to be blown across the evaporator coil bringing in fresh outside air into the cabin.
When in the max AC position, the fresh air vent is closed forcing the blower recirculate the air in the cabin. Because it is recirculating the cabin air instead of bringing in hot air from outside, the air is supposed to cool down. I believe the fan sounds faster because it is actually louder when the air is forced to be drawn in from the inside recirculate vent.

So while we both agree that the fan sounds louder/faster, and the air should be colder, I can see no way the electrical circuit speeds up the blower motor when in the max position. If you or anyone else can see it on the diagram, please let me know what i am missing.

This is the 88 electrical diagram. Notice the function selector switch terminals X and W are for the compressor clutch circuit. Terminal Z and Y are for the blower fan.
Z is feeding power to the function switch. Y is carrying power to the blower motor relay in every position except off... That is it! The relay is either open or closed... There is nothing in that circuit that can change the blower motor speed. The circuit being opened and closed by the relay is the fused link circuit that actually feeds the blower motor. It is 12 volts period.

So though we know the motor sounds louder and blows more air, it is not because of the electrical circuit.



This is the diagram for the 1985 in case yours happens to be wired this way. Again the only difference is that there is no blower motor relay or fused link circuit and blower motor, ac compressor clutch, and control circuit are all being feed of of a single 35 amp fused circuit.
NOTE. I think there is a problem with this diagram. According to the selector lever diagram for the AC clutch circuit terminal #3 is MAX AC and terminal #4 is NORMAL AC. Notice the 12v feed is marked Z and when it connects with terminal #3, it feeds power to the compressor clutch. BUT there is no connection from terminal #4 to the compressor clutch! Going by this diagram as it is, the compressor clutch would not be engaged when terminal Z connects to terminal #4 and the selector lever in in normal AC position...

 

The fuse is 35 amp so the vent system should be '85. I see what you mean on the circuit diagram. It doesnt make sense to me to have a max setting but not an increase in air flow. If the resistor blower control has 3 resistors- low med and high. I would think it should have a 4th for the max setting on the a/c. It also doesnt make sense to me that when the a/c is on you would want any of the hot outside air to be let in on any setting.

 

On the 1985 duct system there is a vacuum control to the left of the passenger a/c vent. Does it control the air flow to the vent?

 

Well I have learned a bit more about how the vent system works on my vans while helping you with this, I have not dug into it this deep before! Now I understand how works works..

Ok another clue to what system you have is, the blower fan on the 85 is under the dash on the passenger side. On the 88, it is outside under the hood mounted to the evaporator housing.
So where is your blower fan?
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1- “It doesnt make sense to me to have a max setting but not an increase in air flow.”
2- “ It also doesnt make sense to me that when the a/c is on you would want any of the hot outside air to be let in on any setting. “

Ok these two tie together.
1- The air flow coming out the vents does increase when the selector lever is in the MAX position and the fresh air vent door is closed. It does on my van and my Saturn. The only answer I can think of is that it has something to do with the way the air flows when the vent door is closed. I will include a vacuum motor test chart which shows what doors should be opened or closed depending on what position the function selector is in and the temperature selector.
Perhaps you can see something that I am not seeing, like a different vent door opening or closing.

2- The diagram below shows that the Fresh Air Vent is opened ALL the time except when the selector lever is Off or in the Max AC position... So the system is designed to operate with the fresh air vent opened in most of the time. It closes only when the selector lever is in the MAX position. this is to recirculate the cabin air to cool the van down faster. i have been reading and there are several reasons for this.
I always ran my Saturn on MAX AC and I started noticing after a couple of months that it would smell moldy when I first turned the AC on. I went to the Saturn board and they said not to run it on max all the time. It causes the ducts and evaporator box to sweat or condensate forming mold inside. They advised running the ac on normal so the fresh air vent would open and dry out the condensation.
Another reason is, picture a 12 or 15 passenger van with good door and window seals and 12 to 15 people breathing inside that little box. Besides breathing the same air over and over, the humidity would go up and the inside would start to sweat.
There are several other reasons if you do a search on “what is the difference in max and recirculate”. (it’s ok, I just learned this too!)

“On the 1985 duct system there is a vacuum control to the left of the passenger a/c vent. Does it control the air flow to the vent? “
The diagram below should help with this question. There is vacuum motor over each door except for the temperature blend door which is operated from a cable to the temperature selector.


OK now to the drawing. I do not know if this is another mistake on a drawing or if it is meant to be, perhaps you can help me out here..
On the Vacuum motor Test Chart I marked a red circle around around the part in question.
It is my understanding that the vacuum motors are spring loaded and the doors will close when there is no vacuum to them.

On the test chart I marked recirculate door position with a green rectangle. As expected there is no vacuum to the fresh air door motor when the function selector is in the normal position. The negative sign (-) means no vacuum.
BUT under the HEAT-AC column I marked with a blue rectangle, there is a difference between max and normal for the AC/Heat door #6. When the function lever is in the Max position it shows that door #6 opened regardless of where the temperature selector lever is.
On Normal though, the chart shows that door #6 closed (- having no vacuum) when the temperature lever is in the 1 or 2 position and opened when the tempature lever is in the 3 or 4 position. Again the (-) represents NO VACUUM. If that door has no vacuum closes, the air can not flow through the panel registers. That door is either opened or closed unlike door 7 for the heat/defrost which has a partial position. That partial position on the heat/defrost door allows air to flow through the heat and defrost vents when you have the function lever in the MIX position..
So look at this and see if you can see something I am missing in the vent system that might account for the stronger air flow when the function lever is in the MAX position because i cant see it...

 

Is the one in green the one you are talking about? IF so it is the vacuum motor for Door #6.. Also seen in the picture of the duct work earlier up in our posts. With vacuum applied it closes off the heat/defrost vents and forces the air out the AC vents

 

A thought on the right side vent before you remove the dash...
I think you said you have replaced the blower motor before?

What if you removed the blower motor, could you reach your hand up inside the opening and feel to see if the right vent duct work is connected?
I suspect the AC/Heat door may be in your way but you should be able to push the lever to the vacuum motor and move the door out of your way. Perhaps the vent is clogged up. You would be surprised what can get inside those things..
If it is disconnected, perhaps going through the blower fan area and the vent register itself, you could reconnect it? I don't know but it seems like it would be worth a shot before attempting to remove the dash!

 

It has 4 speeds now. I redrew the circuit so maybe it is a bit easier to see.
Remember the 12 volt power is supplied to the motor from the Function Selector Lever. The only time the blower motor does not have constant 12 volts is when the FSL is in the off position.

The fan speed switch is switching the ground side through the resistors and to the blower motor.

Notice #1 terminal on the blower speed switch makes no connection to the resistor. That is because the ground (blue) is always connected to R3. The fan speed switch does not have an OFF on it, it starts on LO. It does not need an off because the FSL has the off. So anytime you move the FSL from the off position the blower motor is on low position, providing the fans speed switch is in the down position.
The ground is feeding through R1, R2, R3, and then to the motor.
Medium low, yellow, #2 terminal is feeding through R2, R1, and then to the motor.
Medium high, Red, #3 terminal is feeding through R1, and then to the motor.
High, Green, #4 terminal has no resistor and feeds directly to the motor.
There is no way to get any more speed out of the motor..

I guess it could be rewired to only go into high speed only when the FSL is in the MAX position but then you would not have high on the other settings, so that would be useless.

Again according to the drawings for the 85 and 88, the reason more air comes out the vents when the ac is on max is due to something in the vents, not the electrical. I would like to find the answer to this too!

I went out and played around with my 88 and no matter what position I had the temperature selector in, air only blew out the front vents with the FSL on max or normal. No air came out the floor or defrost vents on max or normal.

As to why yours is not blowing out more air when you go from normal to max, perhaps one of the doors is getting stuck, the foam seal on it is bad, the vacuum motor is bad, one of the vacuum lines is bad or off, or something in the FSL.

 

The fan is under the passenger side dash. Easy to get to. Yes that is the vacuum seleniod I am referring to. It might be off the door latch just as the one to the outside air door was. I havent looked yet so I dont know how easy it is to get to to check. I notice on the vacuum selenoid that controls the outside air door- I see the vacuum lever pushing the door latch back and forth but I dont see the door acually opening and closing. It looks like it is in the closed position.
That is a good idea, I may have to take the blower motor out to get to the vent connection. It is probably that or the vacuum lever is off the door latch. I really dont want to take the entire dash off. The van had factory air when I bought it but some of the hoses were disconnected so I replaced the entire A/C system with all new parts including the compressor. Retrofitted it to accept R 134 but the air never really came out all that cold. The mechanic I go to said if I was able to use R-12 I would be freezing. I know the R 134 doesnt work as well in the system but It should get colder than it does. I put a thermomator against the center vent and it showed about 55 degrees. The sticker on the hood says 3.5 pounds of refrigerant to fill the system but I put 3.5 pounds in and the gauge showed it barely out of the low range.