Intermittent A/C Problem - Bad Relay? - Defender Source
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  #1  
Old August 20th, 2011, 08:55 AM
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Intermittent A/C Problem - Bad Relay?

I have an intermittent air conditioning issue on my 1997 NAS D90. 2 Things happen and they are probably related.

Sometimes (even when the AC is turned off) I can hear what sounds like a relay switching off/on RAPIDLY. It clicks in pairs very quickly. CLICK-CLICK <Pause 1/2 Second> CLICK-CLICK <Pause 1/2 Second> CLICK-CLICK - etc. Sometimes it goes on for a minute or two. The sound is coming from being the A/C unit in the cab from the right side of the passenger foot well.

The second thing is that it sometimes doesn't cool. (It's a bit of a problem here in South Florida with the full top on. My last truck didn't have A/C if that helps redeem myself!) I can't seem to make sense of it - sometimes it works sometimes it doesn't. It doesn't seem to have to do with whether or not the truck is hot/cold or has been running a while. It just decides it wants to crap out and blow warm air. Then I'll hear the compressor (?) kick in and cold air starts flowing once again - sometimes after being "dead" for 5-10 minutes. The outages don't seem to last long. It works more than it doesn't but obviously this isn't "by design." Ideas?

Note that when the AC dies I don't hear the relay freaking out. I just stops cooling. I would assume these issues suggest an issue with the AC but are they directly related?

Could this be as simple as a bad relay or something more complicated?
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  #2  
Old August 20th, 2011, 10:17 AM
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Verner Berry
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I had the same issue minus the clicking. A/C shop said the system had a block in the lines somewhere, they drained the system and refilled it with the correct amount. No issues since (about a month ago) blows ice cold with ambient temps of about 80 degrees.
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  #3  
Old August 21st, 2011, 08:27 PM
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Quote:
Originally Posted by Verner Berry View Post
I had the same issue minus the clicking. A/C shop said the system had a block in the lines somewhere, they drained the system and refilled it with the correct amount. No issues since (about a month ago) blows ice cold with ambient temps of about 80 degrees.
I appreciate it. I'll take it to an AC shop and see what they can make of it. Today it was working great but when I started the truck up after lunch it didn't work but then after about 5 minutes of driving it started cranking cold air. Strange!
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  #4  
Old August 21st, 2011, 09:07 PM
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mark kellgren
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I think you may have a bad connection in the A/C main harness, and it is having intermittent connection issues. look for the big brown connector.

your systems "cools" when the compressor is on and active. The thermal probe by the evap coil in the A/C compartment in the passenger footwell tells the A/C ECU what the blowing A/C air temp is, and once it gets too cold, then the ECU deactivates the clutch on the compressor to prevent frosting. that is why a compressor cycles on and off constantly, which is normal. interruptions in the electrical harness will disrupt that normal cycle. you should however have the A/C system checked for refrigerant. if they confirm the correct amount is in there, then you can focus on electrical faults.
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  #5  
Old August 21st, 2011, 09:39 PM
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Julien Dalbin
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Tri-valve pressure imo.
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  #6  
Old August 22nd, 2011, 06:27 PM
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Your drier might have imploded and sent the drier material through the system, plugging the expansion valve, thus causing buildup and eventual blockage of fluid after a few minutes of flow.

My D blew ice cold for 5 minutes on startup, then would blow warm. I had the system checked, and was told that there was a blockage in the system. They recommended replacement of the Drier and Expansion Valve......at a cost of "somewhere between $750 and $850 dollars." After some probing, they admitted that they had no idea how much the parts would cost or how long they would take to complete the job. All they saw was multiple Rovers and probably decided I was a fool that would pay whatever they wanted. I've never run into so many corrupt auto shops except here in Columbus, Georgia. Heck, I get better service at the local Stealerships. I miss Seattle and Boise... I digress, anyway,

I took off the Drier and the Expansion Valve (pain in the butt), and flushed the condenser, evaporator, and lines individually. The line coming from the drier into the expansion valve (had a small screen in it) was completely covered in crud and looked like it was probably the culprit area. When I went to fit the aftermarket drier, I found that it had male and female ends, not the two male ends the factory drier had. Also found that the expansion valve looked drilled incorrectly in one of the orfices.

I ordered a factory drier from Atlantic British today, and a different aftermarket expansion valve from Metrix. Hope this works.

And to reiterate, taking the plastic cowl off the condensor surround in the cab was excrutiating. Especially the screws holding the blower in the back.....or I am a complete retard which wouldn't be the first time.
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  #7  
Old August 22nd, 2011, 09:59 PM
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errr..... meant evaporator, not condensor in cab.....
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  #8  
Old August 23rd, 2011, 09:24 PM
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Probably talking to myself, but BLUF, the factory drier, for 1997s, will not work. From what I can gather, there is an issue with thread type on this "updated" drier and the line from the trinary switch. I'm going to drive the 200 miles round trip to Hotlanta to have a reputable AC shop look at it. Guessing they will replace the line and/or fitting that goes to the drier to make it compatible. Hopefully, they can use the new drier I got from AB. At this point, I'll pretty much do or pay anything.

I'll post results if anyone is interested. I'm guessing I'm not the only one with drier/expansion valve issues, unless I'm that lucky one, again.
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  #9  
Old August 24th, 2011, 06:54 PM
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Thanks everyone for the input. When I get a nano-second free I'm going to take the truck to an AC place and see what they say. I'm clueless when it comes to A/C so having a bit of info in my pea-head is helpful.

Will post the results here.

Thanks!

Hutch
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  #10  
Old August 24th, 2011, 10:38 PM
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Mike Doligalski
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Hutch,

I think taking the truck to an AC shop for analysis is a great idea. I've dabbled a little with AC repairs in the past- had some lines rebuilt this spring, bought a new drier, re-oiled the system, evacuated the system, and recharged- but am by no means an expert. You're problem sounds a little more involved than mine was but my gut says that you've got some kind of blockage and/or problem with the expansion valve. Would love to hear what the shop comes up with.

BTW, I'm new to the Tampa area, and I've got a vacuum pump that you're welcome to come over and use if you decide to tackle the fix yourself. Whereabouts in the bay area are you?

-Mike
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  #11  
Old August 25th, 2011, 04:36 PM
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Severin Blenkush
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A/C repair

I went through A/C replacement part issues just recently. On the '97, the "original" drier is no longer available (or, I think, made - Moog was the manufacturer and they no longer list the part #). The "replacement" drier has a different thread pattern than the trinary pressure switch. The new pressure switch is hard to locate (found 1 source on-line) and is about $400. I looked for adapters to try to get the old pressure switch to a new drier - no luck. The female thread pitch on the switch is 10mm x 1.5. No one makes anything that can convert it (that I could find). I ended up going to Autozone with my old drier and had them match one with the same layout ($24 I think) and had a machine shop make a female to male adapter ($15) so I could use my original pressure switch. I got that together, took it to a shop and charged the system to find out I needed a new compressor (rebuilt on eBay for about $200). Will report back when that is installed.

For reference:

old trinary switch STC3976 fits drier STC3973

new trinary switch 8510066 fits drier STC4851

compressor Nippondenso 10PA17C #77392

Cheers,
Severin
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  #12  
Old September 6th, 2015, 08:27 PM
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NAS 110 AC relay location??

So can someone tell me where the AC relay is located on a NAS 110? I have had the flickering sound for about a year and it appears to be coming from behind the middle dash around where the round gauges are. Can someone please confirm that? How easy is it to access it to change it out? Yellow or brown relay? I just don't want to blow the compressor out like I just did on my DI?
Thanks,
Ed
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  #13  
Old September 6th, 2015, 08:52 PM
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I can't help you on your question but my intermittent A/C issue in my 110 was the switch button was not always making contact when depressed.
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