98 mercury mountaineer 5.0 hvac problem | Ford Explorer Forums - Serious Explorations

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98 mercury mountaineer 5.0 hvac problem

porsche356

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Year, Model & Trim Level
96 ford explorer 4wdsport
does anyone have a full diagram for the hvac power circuit for this vehicle? the high and low pressure switches have been checked and bypassed but no power reaches the ac clutch. i need to know where the signal leaves from the switch all the way through so i can find the break or problem component.....checked fuse in cab and underhood and swapped ac relay out with horn relay so relay is also good. is there another relay somewhere? any and all help will be greatly appreciated need to get the hvac fixed for my wife and kid thanks again
 



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Do you have the manual HVAC controls (3 knobs) or the EATC (automatic) controls?

Have you tried running a 12V jumper wire directly to the A/C compressor clutch?

If you have the EATC controls, there is a small relay on the circuit board inside the EATC unit. This relay engages the A/C compressor clutch. The relay has been known come loose of the circuit board, but can be re-soldered.
 






if i pull the ac compressor relay under the hood and apply a ground to i think pin 4 or 5 then the ac clutch engages.....not getting the signal to turn the relay on...and manual knobs
 






if i pull the ac compressor relay under the hood and apply a ground to i think pin 4 or 5 then the ac clutch engages.....not getting the signal to turn the relay on...and manual knobs
so yes i know the clutch itself is ok its a control issue....even bypassed high and low pressure switches for testing
 






Have you checked your Wide Open Throttle relay? It's supposed to cut out the A/C Compressor at WOT to provide max engine power when passing.

I have a set of Explorer wiring diagrams I'd downloaded that includes the A/C system, but I don't know how to attach it to your thread (it's a ZIP file). Maybe someone else here can provide you with the diagram you need.

Below is what I have, maybe if you blow it up you can read it.

upload_2019-7-20_17-39-24.png
 






i am almost positive it could be another relay ...when i got it it had sat for about 2 years long story short the power windows wouldnt work ended up being the timer relay that controls the dome light and main power to the window switches.also i have no highbeams...where is the wot relay located and if i pm you my email would you mind sending me the zip file...Also tyvm for your help thus far.
 






first thing i want to do is check the signal leaving the manual controls.blower works so im really doubting there is going to be a problem there , i am betting on a relay somewhere thats hung or just bad
 






Okay, I can attach the ZIP file of all the Explorer wiring diagrams to an email and send it to you. I open it using File Explorer and the individual Adobe files are then shown. The diagram for the A/C system is the first file. PM me your email address.

Edit:
See if you can open the below attachment.
 

Attachments







i apologize for the late response i got sent to maryland for work and just got back.will be looking at this tonight and working on it tomorrow will let you know how i make out.....one question where are the relays including the wot located thanks again for the help
 






i apologize for the late response i got sent to maryland for work and just got back.will be looking at this tonight and working on it tomorrow will let you know how i make out.....one question where are the relays including the wot located thanks again for the help

Do you have an owner's manual? That should show you where the various relays are. Most (but not all) located in the power distribution box near the power brake booster. If you don't have a '96 owner's manual you can probably download one.
 






no no owners manual lol trying to figure out how to pm you
 












if i am looking at the diagram right the switches i called high and low pressure are actually ac clutch cycling and ac pressure..those are jumpered so those can be ruled out as the issue correct? if i remember rt the problem is going to be either pin 1 or 2 of the ac relay not getting gnd to make the relay operate ill have to try with a test light again tomorrow and see which lead it was that operated the clutch . it wouldoperate if i had the test light to gnd of the battery and touched one pole of the relay but i dont remember which pole ..once i know that it should lead me to either the pcm power relay pin 87 or the pcm itself pin 69 correct?
 






if i am looking at the diagram right the switches i called high and low pressure are actually ac clutch cycling and ac pressure..those are jumpered so those can be ruled out as the issue correct? if i remember rt the problem is going to be either pin 1 or 2 of the ac relay not getting gnd to make the relay operate ill have to try with a test light again tomorrow and see which lead it was that operated the clutch . it wouldoperate if i had the test light to gnd of the battery and touched one pole of the relay but i dont remember which pole ..once i know that it should lead me to either the pcm power relay pin 87 or the pcm itself pin 69 correct?

Yes, there can always be differences from year to year.
 












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