A/C problem

I may not be following protocol by posting this, but I could use some help and this forum seems to have some good feedback. I am a Windstar owner (repairer) but I also have a '90 Nissan Pickup with an A/C problem. The on/off switch on the console lights up when pushed, but I get no A/C. I checked the fuse--checks o.k. I checked the compressor and the clutch does not engage. I am looking for a starting point to test. How do I test for power at the compressor? Should I check the relay or thermostat switch and if so how?
Again, sorry for the improper posting, but I posted this on the Nissan forum and got no reply.

There is information that may help you in this thread....
http://www.automotiveforums.com/vbulletin/showthread.php?t=565417

The title (in case the link does not work) is " windstar battery "
The person had a problem with their A/C compressor not engaging....and there are tips on what to look for.
Your Nissan is likely different.....but may be close.
The Windstar has 2 pressure switches that have to be in the correct state in order for the compressor to engage.
1 is the high pressure switch that prevents damage caused by a over pressure condition......which is located down near the compressor.
The other is a low pressure switch that prevents the compressor from engaging with too low of a system pressure at that point......which could be too cold of weather or the evaporator coils (cold coils) being too cold....to prevent them from icing over....this switch is located on the accumulator.
The PCM has control over the A/C compressor also, such as full throttle "A/C cut off" to give your engine full power when you push the accelerator down all the way.....such as to pass.
Of course, if you have lost the A/C system "charge", your compressor may not come on either (I am guessing, but the low pressure switch may serve that function as well).

Thanks Wiswind. What do think of testing the compressor right from the battery to eliminate it as the cause? I saw mentioned in your link that the pressure switches could still prevent the compressor from running? ALso, is there a way to tell if the system has lost its charge which may also prevent the compressor from running? I am trying to eliminate the easy stuff first before I really dig into this.
I'm not sure, but I think the Nissan system is not as high-tech (over-engineered?) as the winny. From what I can tell as far as the schematic, the I/O switch is controlled by a thermo switch and a relay. I don't see anything that shows it controlled by PCM.

Thanks Wiswind. What do think of testing the compressor right from the battery to eliminate it as the cause? I saw mentioned in your link that the pressure switches could still prevent the compressor from running? ALso, is there a way to tell if the system has lost its charge which may also prevent the compressor from running? I am trying to eliminate the easy stuff first before I really dig into this.
I'm not sure, but I think the Nissan system is not as high-tech (over-engineered?) as the winny. From what I can tell as far as the schematic, the I/O switch is controlled by a thermo switch and a relay. I don't see anything that shows it controlled by PCM.

Hi
the easiest way to tell if there is no freon is with a guage. Being a '90, I believe you have an R12 system (old freon). I am not sure if finding an R12 guage is very easy anymore, but if you can lay your hands on one it is the surest way. You should be able to "hotwire" the compressor clutch from the battery. If you can get at the connector on the compressor easily, see if you can backprobe into the connector on the positive side with a pin or nail, and then touch that to the hot wire to engage the clutch. If you cannot do so at the compressor, I have done it on an '87 Ford at a connector further upstream and more accessible. If you give it power it should engage immediately (it is simply and electromagnet). If you are sure where the clutch cycling switch is , you can unplug it and "short" it's connector to the same effect. That will tell you the clutch is operational but not that the compressor is necessarily good. If you can successfully power the clutch while the engine is running, you can surmise if the system/compressor is operational, and that there is freon, as it will make cool air and/or the suction line will get cold to the touch. As Wiswind said, I would guess that if you get the compressor successfully running you will find that it will not make cold air/will not have a cold suction line as the freon is likely low or gone. In that case you really have no choice with R12 but to go to a mech for R12 service or do/have someone do an R134A conversion. I don't know how well the conversions work, but I do know R12 is really, really pricey.

Perhaps before you start: look carefully over all the A/C components and hoses. Look very carefully at the condenser and all connections. If you see a lot of oily residue anywhere it probably indicates a freon leak. If you don't already know so, there is quite a bit of oil in the freon lines and components. I visually located a large leak on a previous vehicle I owned (in the condenser) and was able to replace that and restore the system.

Best of luck

One question: did you lose A/C rather suddenly, or has it slowly lost effectiveness? Slow deterioration would of course point to freon loss.

Thanks busboy for the info. I've only had the truck about 1 month, so I don't know how the A/C was lost. I knew it was not working when I bought the truck. The truck spent all of its life in Florida so it is likely that the system is out of juice due to extended use. My question is will the lack of freon cause the clutch/compressor not to engage? I would think that if it didn't, then I'm definitely looking at a electrical malfunction?
Its not a big deal if I get this fixed or not seeing as how the truck now resides in sunny Buffalo, NY. But it would be nice to have if it is easy and reasonable enough to fix--otherwise the truck is in great shape.

You mentioned the clutch cycle switch, would that be what I am seeing on the schematic as the thermo-switch behind the dash?

Thanks busboy for the info. I've only had the truck about 1 month, so I don't know how the A/C was lost. I knew it was not working when I bought the truck. The truck spent all of its life in Florida so it is likely that the system is out of juice due to extended use. My question is will the lack of freon cause the clutch/compressor not to engage? I would think that if it didn't, then I'm definitely looking at a electrical malfunction?
Its not a big deal if I get this fixed or not seeing as how the truck now resides in sunny Buffalo, NY. But it would be nice to have if it is easy and reasonable enough to fix--otherwise the truck is in great shape.

You mentioned the clutch cycle switch, would that be what I am seeing on the schematic as the thermo-switch behind the dash?

Hi

to the first question I would say yes. The system should not run if the freon level/pressure is not above a minimum. That pressure has to be measured by a sensor/switch of some kind. I did a bit of looking online at a parts house for '90 Nissan pickup and saw a Thermal switch, and a pressure cutoff switch. I would be surprised if the switch which cycles the a/c compressor clutch on your truck is located outside of the engine compartment, but I have zero experience with Nissan, or any other Japanese manufacturer. Ford switches sense actual freon system pressure on the low and high side. The low side switch cycles the compressor clutch on and off. If I had to guess at the Nissan part equivalent I would guess the thermal switch, as the pressure cutoff switch to me implies that it is a limiter, or a high pressure cutoff switch - but I am only guessing.
I would start at the compressor and go each direction - high and low pressure. The high side line should head from the compressor toward the condenser (small "radiator" usually mounted ahead of the actual radiator). The low or suction side should run from the compressor up to the firewall - of course the freon on that side is actually running the other direction being suctioned from the evaporator core inside the truck. As Wiswind suggested, I should think you will find a sensor/switch along each "side". One should limit the high side pressure, the other should sense the low. The one on the low side likely controls the comressor clutch - unless Nissan contols their systems completely differently. You may also be able to tell by which switch's wires are the same color as those at the a/c clutch - assuming Nissan matches them up.

Good luck to you. I have had the a/c blasting many times in BUF. It can be pretty warm and sticky over there.

Thanks busboy for the info. I've only had the truck about 1 month, so I don't know how the A/C was lost. I knew it was not working when I bought the truck. The truck spent all of its life in Florida so it is likely that the system is out of juice due to extended use. My question is will the lack of freon cause the clutch/compressor not to engage? I would think that if it didn't, then I'm definitely looking at a electrical malfunction?
Its not a big deal if I get this fixed or not seeing as how the truck now resides in sunny Buffalo, NY. But it would be nice to have if it is easy and reasonable enough to fix--otherwise the truck is in great shape.

You mentioned the clutch cycle switch, would that be what I am seeing on the schematic as the thermo-switch behind the dash?

The refrigerant in an AC sytem is a closed system and does not run out of juice due to usage but may leak due to a system integrety fault. If you cannot get hold of a gauge you can probably get it tested for about $30.

My daughter has a '92 Nissan pickup and about every 2 years I have to replace the two add-on relays under the hood that control the fan and ac clutch. I'm sure only one relay fails at a time, but I just replace them both as opposed to doing the extra trouble shooting. If your layout is the same, you will find the relays attached inside the passenger fender well ... close to the hood hinge.

Other than the relays, the ac works perfectly ... and there has never been any refrigerant added ... I check it every cooling season.

Hope your fix is as easy as just the relays.

BTW, if you price the relays, complete with little metal bracket, at Nissan, you will be quoted $80 (each) or so. If you pull off the brackets for reuse and price only the relay, you will be looking at less than $15 each.

Thanks to all for the feedback. Just noticed that the system has already been converted to R134.

Here are the test results. Before I did anything, I depressed the needle valve on the high pressure line and nothing came out. Is this signifigant? I hot wired the compressor and it kicked on. I let the compressor run for about 5 minutes and checked the lines. Nothing was cold. I tried the needle valve again and got a very short burst of air. Tried this twice with same results.
Do I assume that there was a leak and I'm out of freon, or could the compressor possibly be junk? I see no visible traces of leaks, but is hard to tell due rust inhibitor sprayed into the engine compartment.
What should I expect to pay for a leak test and/or a recharge. Do the recharge kits from Autozone work or not worth it?

[QUOTE=pitteach]Here are the test results. Before I did anything, I depressed the needle valve on the high pressure line and nothing came out. Is this signifigant? I hot wired the compressor and it kicked on. I let the compressor run for about 5 minutes and checked the lines. Nothing was cold. I tried the needle valve again and got a very short burst of air. Tried this twice with same results.
Do I assume that there was a leak and I'm out of freon, or could the compressor possibly be junk? I see no visible traces of leaks, but is hard to tell due rust inhibitor sprayed into the engine compartment.
What should I expect to pay for a leak test and/or a recharge. Do the recharge kits from Autozone work or not worth it?[/QUOTE
If you opened the high pressure port before anything else, your freon is gone. You should have something on the order of 40-60 psi on a static system. If you take it in, I think the first thing they will do is use a vacuum pump to pull a vacuum on the system. The last time I had to have a system serviced, it had to hold a certain vacuum level for a certain time before they could "legally" add freon (R12) to the system. If it cannot hold a vacuum, it has a leak and they must deal with that before they can re-charge it.

You might try an independent shop and work something out: ie, how much to put your vacuum pump on it and tell me if it has a significant leak? Then, go from there. If you live in the Amherst area, my father in-law has had good luck at Hubert's on Harlem Rd. I would guess most "known" places would quote you their basic A/C service rate at a minimum. And, if the system will hold a vacuum, and you add R12 freon, they sell it by the ounce. I will venture a guess that your system holds 1-1.5 lbs. I could not tell you the per ounce price now for R12, but I am guessing $6-$8.

Again as to the conversion kits, I don't know. You mech could guide you on that.

Good luck

Thanks busboy,
The system on the truck has been retrofitted already for R134A. I mis-spoke before when I used the term freon, I have learned that R12 is commonly called freon. I have a local shop that I"m sure will run a vac test. I would rather check for leak before adding costly oil.

Thanks busboy,
The system on the truck has been retrofitted already for R134A. I mis-spoke before when I used the term freon, I have learned that R12 is commonly called freon. I have a local shop that I"m sure will run a vac test. I would rather check for leak before adding costly oil.

No problem. Glad to know you already have 134a. Much more cost effective. You can buy it in the store for around $6-9 for a 12 ounce can for "topping off" this time next year.

I am trying to figure out where the low pressure side of the ac system fill valve is so I can add 134a on my 2001 Windstar. Any pictures showing the system and the components?
ThanksNo problem. Glad to know you already have 134a. Much more cost effective. You can buy it in the store for around $6-9 for a 12 ounce can for "topping off" this time next year.

pitteach you can actually add freon with a dye in it then look for the leak yourself, but don't add the whole can since your system has a leak. most leaks are due to a faulty o-ring or a leaking line(where hard line turns into soft line). after you find the leak and repair it then you take it to the shop to get the system evacuated and rechaged.

I am trying to figure out where the low pressure side of the ac system fill valve is so I can add 134a on my 2001 Windstar. Any pictures showing the system and the components?
Thanks

Hi

I looked at an engine compartment photo on Ebay for an '01. From what I could see, the low pressure port was visible on the inverted U shaped A/C suction line located to the rear on the passenger side of the engine compartment. It has a small black screw-on cap. There is another similar black capped valve on the end of an aluminum tube that comes up and ends just beside the coolant recovery tank, and is forward of the low pressure valve. That should be the high pressure valve. It is a different size and you should not be able to mistakenly attach the fill line to it. Here is the link for the photo if it helps.

http://cgi.ebay.com/ebaymotors/2001-Ford-Windstar-SE-Quad-Seating-Low-Miles-Loaded_W0QQitemZ4645372273QQihZ002QQcategoryZ6225Q QrdZ1QQcmdZViewItem