basic a/c troubleshooting for 1992 toyota corolla

i use chilton's to do a fair amount of work on my 1992 toyota corolla(140k,1.6L). but i'm not about to gamble with any a/c stuff.

still, i do have a question about the a/c system as a whole that might help me diagnose a problem.

from one day to the next the a/c went from frigidly cold to non-existant. the belt is not slipping (that i can tell) and the compresor engages when i hit the "a/c" button (i hear the engine idle slightly differently as though a load has been placed on it). fuses are ok, though i couldn't get the circuit breaker out to check it.

years ago this happened when i replaced the alternator. i had inadvertantly disconnected the electrical connector that goes to the compressor. plugging it back in fixed the situation instantly.

yesterday i was wiping off some oil (have a minor oil leak that seeps over time) from the under carriage around the area where the a/c compressor and timing belt cover are. now the a/c isn't cold anymore again.

are there other electrical connections in the area that i might have missed? the line for the alternator regulator (and ground?) is coupled a wire that goes down into the compressor where the belt/pulley is, and from the same spot (pulley) a wire comes up and attaches to the compressor itself (ground?). a second wire that branches off of the alternator wires slides onto a round metal knob (no idea what this connection is for).

if there was a coincidental refrigerant leak (and my activities were unrelated), could it go from frigid air to normal blower air in one day? or would the coldness of the air slowly go bad over time as the leak progressed?

my gut feeling is that the compressor and refrigerant are fine, just that something got disconnected)

are there any other basic, quick check tests for why the a/c coldness suddenly failed from one day to the next? (something that i can check with a voltmeter/ohmeter)

thanks so much for your time,

rxb

Reply to
rxb
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Have you checked the system for sufficient coolant?

Charles of Schaumburg

Reply to
n5hsr

The first thing to check is to see if the AC compressor clutch engages. The compressor has an electro-magnetic clutch, and when it is disengaged, the pulley free-wheels. When the clutch is engaged, the pulley turns the compressor. You can see the clutch engage and disengage if the engine is idling and someone turns the AC on and off while you watch the compressor. If you have trouble seeing this, there is another way to see if the compressor is engaged.

With the AC on, look at the sight glass on top of the receiver-drier, which is mounted in front of the AC condenser, which is mounted in front of the radiator. The receiver-drier is a cylinder with refrigerant lines going in and out of the top, with a clear glass window about the size of a dime on top. If the system is properly charged with refrigerant, it should look like water is flowing from left to right past the glass. If you see anything moving past the glass, the compressor is engaged and electrically OK. My guess is that you will see white foam moving past the glass, which means that some refrigerant has leaked out and needs to be evacuated, checked for leaks, and re-charged.

There are some other possible causes, but for simplicity's sake, I recommend that you start by checking the sight glass.

Reply to
Ray O

OK, I replied to this earlier, but it doesn't seem to be posting. So I'm trying to again. Sorry in advance if this is a repeat post, as I am new to these boards.

First of all, Wow, thanks alot for the info. That's the exact primer I was looking for.

It turns out the compressor clutch is not engaging afterall. So the clear window doesn't show any flow, as I would expect it not to.

Someone said something about a failsafe for the clutch to engage if the charge is low. So it still could be a leak somewhere, I suppose. But it seems that the air going from frigidly cold to plain blower air within one day would only happen with a major leak (car accident?), so I'm guessing that's not the case.

Is there just the one wire (coupled with the alternator bundle) that has the clutch engage? (the return wire seems to be grounded to the compressor body itself).

My feeling is some kind of dirt/grime may have gotten in the clutch when I was wiping stuff off in that area. Is there a voltage drop test to see that the wire is ok? (voltmeter in parallel from wire (before clutch) to ground?)

It seems that the clutch assembly and the internal compressor function have to be reasonably isolated from one another (to keep refrigerant in, and dirt out), so I wonder if I could spray an electrical degreaser in there (with belt off) to clean out the clutch, if indeed I contaminated it with something.

Finally, a few more quick questions about costs. Just shooting for a ballpark idea, so I know what I'm getting myself into.

Leak check ? Refrigerant recharge ? To replace the clutch alone? (assuming it can replaced without replacing the entire compressor?) - or is the clutch itslef a job that I could do myself ?

I can't thank you enough for your information.

-richard (rxb)

Reply to
rxb

Already replied to the OP's e-mail.

Reply to
Ray O

A leak big enough to find with soap bubbles would not take very long before the a/c stopped cooling.

When the compressor is running if the suction and discharge line are even close to the same temperature it is not pumping anything. One should be ice cold and the other should burn your finger so be careful.

GL Dan

Reply to
Danny G.

How the heck can I filter out all the OT posts that do not have the "OT" subject line?

Thanks Dan

Reply to
Danny G.

At present, I see only 2 threads where people forgot to mark them as "OT". Well, technically one - the other was intitally marked as such, but a colon was used instead of a hyphen, so the "OT" designation got lost.

Cathy

Reply to
Cathy F.

"Danny G." ...

Dan - what I do is light up the ones that I want to follow in red, so I can just skip over the chaff. I leave them in as sometimes I peek at them to get a good laugh. It is like a soap opera [grin]. By marking in red I mean that I, when clicked on a message in that thread, do Message>Watch Conversation in Outlook Express. Tomes

Reply to
Tomes

Well, technically one - the other was intitally marked

hmmm, I see about 300 (filtered) new messages from yesterday. 10% are Toyota related and 10% have a OT# that I just added to the filter list.

It's not really a big deal usually. But half the time there are 1,000 or more new messages and I just don't have the time and end up just marking everything read.

Thanks

Reply to
Danny G.

Set your preferences to not expand the threads automatically - so all you see are the headers. Then manually expand the threads you're interested in?

And if a thread veers away from its original topic & becomes OT, right-click one of its posts & hit "mark conversation as read", then hit the "F5" key to refresh & see only the unread messages. At least you'll see less "noise" that way.

Cathy

Reply to
Cathy F.

Well, technically one - the other was intitally

designation got lost.

new messages

are the headers. Then manually expand the threads

one of its posts & hit "mark conversation as read",

you'll see less "noise" that way.

Thanks for the help.

Reply to
Danny G.

You're welcome.

Cathy

Reply to
Cathy F.

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