OT dodge dakota a/c

[fordman]

i have a 88 dodge dakota. daily driver when i have to workor go on long trips. the truck did not have a/cinit wheni got it. i took the entire heat box and all the a/c stuff outof a 90 dakota. it all worked when i put it in. the compressor clutch would lock up when i pushed the button in. this was last fall. i just sucked down the a/c and refilled it. but the a/c clutch woudl not kick in. i had to run a hot wire straight to it to make it lock in and spin. now it works like that if i was to reroute around the interior switch and turn everything on. but i do not want to do that. it could mess something up later. so my question is this why wont it work right now? the fuses are good. i have ran hot wires to everyplace that i could find the wire to the compressor and cut off switch. i also jumped across the cut off switch on the expansion valve. i also changed out the dash controls. and the compressor still will not kick in when the button is pushed. does anyone know what and or where i am suppose to check the next part of this? the only thing i can figure out is that there is no power going to the circut from anywhere. even atthe controls. i checked the controls both sets and they all seem to be ok. but i cant test the switch for the a/c because of the way its made. this is kind of hard to explain. before i make the second half of a book about this can anyone give me any help with this?

[knightfire83]

From what I understand, you removed a complete A/C system from a parts truck and installed it into yours.

I imagine that your also installed the heater-A/C controls from the parts truck.

If your controls are digital or even some manual ones incorporate a relay to run the A/C compressor (high amp draw.)

I think your problem may be that your wiring harness may be just a bit different than the parts truck. You may want to compare the wiring diagrams.

-Or-

Since the newer vehicles have more than one fuse box 1 inside/1outside and your vehicle wasn't equipped originally,
are there good fuses / relays in all the spots required to run the a/c?

I know on my '94 Probe for example, I added factory driving lights all the interior wiring was there but the fuse holder and relay socket under the hood was missing the contacts in the sockets to connect these items...... So I had to modify.

It's just going to be a process of following power to the climate controls and then from that to your A/C system.

[fordman]

the wiring harness is pretty much the same. and the compressor did work right after i put this all in. i didn't have to do any fancy rigging of the wiring. iused everything fromthe parts truck just like you would if you were to swap in a factory a/c for our trucks. what is happeningis that the compressor will no longer come on when you turn it on. you can direct wire the compressor and it will work. it just wont work the regular way by pushing the button . even with the new controls i put in it last night. i did pick up a third control today to give that a try. but i dont think that is the problem. i think i may have a wire shorted out some place. and i need to trace it down. i did some tracing last night and i found some of it. and i power it up where i could. but still nothing. the bad spot is between the expansion valve computer box and the compressor. i did find a wiring diagram at the library today i had a slight chance to look it over. and something said that the wires go to the blower motor resistor. so that is where i am at right now.

[knightfire83]

It use to work now it doesn't. Sounds like a proper function of a fuse or a broken / shorted wire.

I'm curious, did your truck already have the wiring for the compressor under the hood or did you have to install a separate wiring harness for the a/c from the parts truck?

I'm trying to locate a wiring diagram online to see how Dodge wires their A/C.

[knightfire83]

You may want to read this : http://autorepair.about.com/library/faqs/bl802g.htm

I found your posting on dodgedakotas.com, does all of the functions besides A/C clutch on your climate control- heater / fan / vents movement work correctly?

The attached diagrams are for a 1999 model. If yours is similar, there are 2 fuses 1-10 amp 1-20 amp, two pressure switches 1-high 1-low, a relay, and the computer all in the mix.

After reading the above link, I'd start checking at the relay by grounding pin #85 and see what happens. Either way it will eliminate 1/2 the possibilities.

[fordman]

the harness was all there. with the exception of a deicer protection thing? but it did work when i installed it. i didnt have to ad any wiring to my harness. i couldn't find my post on that site when i went back if you find it again could you post it. i am not even sure of my sign up name over there now. and i didn't get a sign up email. or it got deleted by accident.

[knightfire83]

http://www.dodgedakotas.com/boards/gen/27418.html

[fordman]

huh no replies on that site. how nice of them. they didnt even tell me to get lost. we got to checking it out with the diagrams i found at the library. but all that really could be figured out is that the computer isnt turing on the ground circut for the compressor to kick on. i do have a back up plan to make this thing work if it is a computer problem. but i want to get a second opinion before i go riggin in some by pass wires and a manual switch. i'll scan what i have o fthe diagrams and hot link them over here.

[knightfire83]

Well then if the computer wont ground the relay, the problem has to be with the low pressure switch..., wiring, or the climate control panel (not likely since you changed that out several times.)

If it was the high pressure switch, the compressor would likely run for a bit then trip that switch and shutdown.

The low pressure switch will just disable the compressor from ever running at all.

The system is charged with enough freon to run right?

Even if you do bypass the computer, you should wire in the low pressure switch to save your compressor should the refrigerant leak out. (expensive) But I think if you keep troubleshooting long enough you'll fix it.

[m-mman]

I am not a Dodge expert but here are some ideas.

You said that you jumped the low pressure switch and still no activity. This is the main "fuse" for the A/C system that prevents compressor operation without oil.

My best guess would then be the "computer" for the A/C system.

I actually have 4 Geo Metros as daily drivers (dont laugh ) and have added A/C to 3 of them.

Ok go ahead and laugh, I do have 4 Geo Metros

Anyway only one A/C was factory installed. Much like you describe A/C is a bolt in - plug & play proposition. Everything remains the same (pop out the 'deletion tube' and bolt in the evaporator - pop out the dash plug, pop in the A/C button ) All the plugs and holes are already there. INCLUDING the place in the wire harness to pulg in the separate computer for the A/C. (the A/C computer plugs into the (only) wiring harness in series with the main engine computer)

The necesisity for this thing suprised me. The A/C installation does not alter the existing heater system, so what does the computer do? I have never learend exactly but without it nothing works, including the fan.

BUT I have noticed that somehow it changes how the engine runs!

On a 3 cyl/5 speed Metro it is very easy to detect any loss in power. (such as carrying additional passengers ) Well, when the A/C button is pushed the car will barely pull away from a stop! It is lke it is pulling a trailer. It bogs down and nearly stalls.

Hit the button to turn off the A/C and it is an entirely different car. It suddenly has power and pulls away like it should.
I suspect that the A/C computer is somehow changing the ingition timing or fuel injection . . . ?
I dont know why you would need to do that but it happens.

This is most noticeable on the 3 cyl stick cars on the 4 cyl auto cars you can hardly notice.

Anyway, after reading this thread I would suspect that the problem is in the A/C computer not the controls. Those darn things do a lot more than you would ever suspect.

[fordman]

we tried bypassing the low pressure switch. that wasnt the problem. it is now full of freon r134A of course.so it isnt the level of freon keeping it from coming on. here is the diagram. you wil see several diagrams for this. the heat only diagram is wht i had before. the a/c diagram is what i am suppose to have. the third one is for the 2.2l engine. ihaev the 3.9l in mine it should be the top right diagram on the page. the heat only is on the almost bottom to the left. i am going to get a 1990 diagram tomorrow and match them to see what might be different. i am also going down to the dodge dealer and see abotu getting a wot relay. if that is whats missing maybe it will make it work. but i am kind of doubtful.

[knightfire83]

Good to have the correct diagram. I attached a copy of it that I simplified to show whats going on there.

If that diagram is correct your truck has an electric radiator fan. I looked on e-bay for your application and I found it should be a dual fan. The diagram indicates that whenever the a/c compressor is on, the secondary fan motor should be constantly running. It also allows the computer to run both fans regardless of A/C operation. If you only have a single fan then all this still applies to the single motor.

If the secondary fan is not working at all, the compressor relay will not have power, thus no compressor. There is a fuse for the Radiator fan relay, and a fuseable link that runs both of the relays. The place to start would be to find the radiator fan relay and check for power (12v) at the White wire and the Grey wire.

If there is power to both of those at the radiator fan relay, ground the Dark blue w/yellow stripe wire and the fan should come on. If not, then you have a bad relay.

If you ground that wire and the fan does come on then the problem is that the ground signal is not reaching the relay from the computer, which means bad wiring or bad computer.

If notice that your radiator fan(s) has been working correctly, You can check the WOT cutout relay:

Check for power at the relay. To do this you will need to leave the radiator fan relay on so that the fan is running while you test. At the WOT cutout relay, check for power at the Gray wire and the Violet wire. If there is power at both of those, ground the Dark blue w/ orange stripe and the compressor clutch should engage. If not, then you have a bad relay.

If it does engage then that means the ground signal from the computer is not reaching the relay, which means bad wiring or bad computer.

If both relays are working as they should then you need to test the climate control panel. Ground both of the connectors at the low pressure switch. The radiator fan should come on and the compressor clutch should engage. If it does then you have a bad climate control or wiring. If it does not then you have a bad ECM or wiring.

This should pretty much take care of your problem, Let me know what you find out. This has been very interesting.

[fordman]

here's a 1990 diagram. it shows a complete different switch in place of the wot relay.

[knightfire83]

Yes it is quite different. But since you are using the 88' wiring harness, lets disregard the '90 wiring diagram. Make sure you have the correct WOT cutout relay for the '88 and all should be good.

[fordman]

its discontinued from the dealer. i dont think i have one on the truck anyplace. it is suppose to be on the fender withhte fuel and starter relay but its not there. there are three different plug there but i need a relay to put in htere to test if its goign to work. i did find a relay in the junkyard from a full size truck but it is a park throttle relay. i plugged it in anyway. and nothing happened.