A/C Problems

[BigT]

The A/C compressor won’t kick on. There is pressure in the system. I also used a jumper wire to bypass the low pressure switch in case it was bad, but that’s not it. I think it’s a connection or short somewhere. I’ve tried a test light in every A/C place I could probe under the hood, but got nothing.

Last winter I did do some work behind the climate control. Maybe I did something there. I did a search for some A/C wiring diagrams, but couldn’t find any.

Ideas where I should start?

[gadget73]

Its fairly basic. Power comes in to the climate control switch, out to the WOT cutout relay on the driver's side fender, through that to the low pressure switch, from there to the compressor coil. If you don't have voltage at the low pressure switch, check at the WOT relay. If nothing there, its somewhere back at the head unit. If you have power through to theh coil on the compressor, the clutch coil is bad.

[BigT]

Thanks for the info!

I see the relays,



But which one is it? BTW, I see more bare wires (this car is falling apart!)


I have power going to the climate control switch, but haven't checked if power is coming out. Its a bit tight I don't want to cause an arch back probing it.

[sly]

Here's the replays in that corner...

[BigT]

Here's the replays in that corner...

Thanks! That’s what I needed. HOWEVER... I’m currently (electric pun not intended!) stuck.

I was testing out the climate control switch. One of the connectors had an erratic reading. Not a constant flow reading. I made it worse by pushing the connector up and down. So like I’ve done with other switches, I took it apart to see if there was corrosion causing it not to flow that I could clean.

Well it came apart easy and I have all the parts to it, but there’s a little ball bearing rolling around inside. I don’t know where to place it when I put it back together again. So I’m stuck until I get another switch or figure out how to put this one back together.

Doh!

[sly]

I think the ball goes on the switch arm between it and the detent track (for lack of a better term) to help give it feedback. I'm going off of old memories of replacing the vacuum controller in the climate control in my 88, so I may not be remembering correctly.

[BigT]

I think the ball goes on the switch arm between it and the detent track (for lack of a better term) to help give it feedback. I'm going off of old memories of replacing the vacuum controller in the climate control in my 88, so I may not be remembering correctly.

You mean for the Clicky feeling as you move the handle?

[sly]

I think so. Been about 6 years since I messed with that.

[VicCrownVic]

Edit: Yes, the clicky feeling.

If it is the part I'm thinking of, here's a picture of the one that was sitting on the shelf behind me:

The part number changed in 1990, F0VH-190961-AA, but I don't think that switch changed much.


For this one from a '91 Grand Marquis, here is a picture of where the ball bearing goes:

When I remove the ball bearing from the spot in that picture there is actually a spring inside the hole that it under the bearing in that picture.

On the other side it rides in the detents of the selecter plate:

To the right of the detents and ball bearing is the angled/stepped groove where the peg sticking out of the stainless plate rides. That peg is part of the vacuum port selector plate (looks like a little rubber stamp with a maze on it).

[BigT]

Edit: Yes, the clicky feeling.

If it is the part I'm thinking of, here's a picture of the one that was sitting on the shelf behind me:

The part number changed in 1990, F0VH-190961-AA, but I don't think that switch changed much.


For this one from a '91 Grand Marquis, here is a picture of where the ball bearing goes:

When I remove the ball bearing from the spot in that picture there is actually a spring inside the hole that it under the bearing in that picture.

On the other side it rides in the detents of the selecter plate:

To the right of the detents and ball bearing is the angled/stepped groove where the peg sticking out of the stainless plate rides. That peg is part of the vacuum port selector plate (looks like a little rubber stamp with a maze on it).

Yes that's the part and how it looks on the inside. Except mine is cooper and has mounts of grease build up on some parts. Wonder if that was causing my poor readings. Thanks again guys!

[sly]

It might be. You can use some contact cleaner to clean the contacts and wipes after removing the majority of goop with a rag or paper towel and then tab with dielectric grease and reassemble. If that doesn't sort it... replace it. I actually may have a spare one of those (could be the old one from the 88 because I swapped it when I was having issues trying to chase down what was wrong). Let me know if you need it and I'll double check the part number I have.

[BigT]

It might be. You can use some contact cleaner to clean the contacts and wipes after removing the majority of goop with a rag or paper towel and then tab with dielectric grease and reassemble. If that doesn't sort it... replace it. I actually may have a spare one of those (could be the old one from the 88 because I swapped it when I was having issues trying to chase down what was wrong). Let me know if you need it and I'll double check the part number I have.

Will do!

[BigT]

I put my climate switch back together, after I cleaned off all the old caked on grease, used a l000 grit sand paper, and put on a light coating of Dielectric. The contacts have a solid flow now, but it did not fix the problem. When I put the ignition switch to AUX, I get the compressor clutch to engage. When I put the ignition switch to RUN, it does not engage. So I took a look at the relays. I get power to each of the relays, one relay in the AUX position and the other relay in RUN position. I think the relay getting the RUN power is not working (the 1st relay is also gets power to it in the RUN position).

The relays are unique with a slot in different positions to match the connectors. I found two parts online. Looking at the parts, they look square without the slots. I take I will need to modify my connectors or the relays to get them to fit? Should I replace them both?

http://www.autozone.com/electrical-and-lighting/relay-a-c-clutch/duralast-relay-a-c-clutch/155070_0_0/?checkfit=true

http://www.rockauto.com/en/catalog/mercury,1986,grand+marquis,5.0l+302cid+v8,1197064,electrical-switch+&+relay,a/c+compressor+relay,3180?a=Referer+www.bing.com+URL+%2F

[sly]

The AC WOT relay is a cutout relay. It will only trigger to cut off the AC clutch. You can jump pin 3 and 5 to bypass it if desired. The replacement relays are made to clear the keyed tabs on the original harnesses so that relay will work in all of those wonky harnesses in that corner. If the car runs, the ECA relay is fine and so is the fuel pump relay. The A/C WOT relay sometimes get's worn out and will cause heat issues on the leads. Sometimes they just crap out. The A/C WOT relay should only be getting power when the AC is on. The coil should only be getting power in run (when the ECA relay that powers all the other relays is on). It is low side (ground) triggered by the ECM so it should always have power in run. It will also only get power when the low pressure switch is letting the compressor run. Also, I'm not sure about this, but in RUN, the car may actually need to be running to get the compressor to engage as the ECM is active and may disengage the AC clutch by triggering the WOT relay unless the engine is actively running.

Here's a crappy ATC diagram (the clutch circuit should be the same no matter ATC or manual controls) that I found on-line:


Attached is which relay is which.

[BigT]

Sorry, I didn't mean to make it sound like I did all of this without the engine running. I did it with the engine running too It runs fine, fuel pump and all. Just no power to the A/C compressor when running. I thought it weird that the compressor clutch would engage in the AUX position though. Tested with the light too, and power to the compressor in AUX, but not RUN (or engine running).

Thanks for the info! I might not be able to jump the pins tomorrow, but will try the next chance I get. If the relay is just for the WOT, then I can bypass it permanently?