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eaglefan63
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Apr 28, 2010, 9:24 PM
Post #1 of 8
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'91 Chevy S-10 AC issue
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1991
Chevy
S-10
V6 4.3
When I tried to turn the ac on it pulled the motor down (as in the voltage meter looked like it had taken up bungee jumping), so much so that it was necessary to give it gas at stoplights or it would stall.
I turned it off, got home and unplugged the wires leading to the ac. Now the vent still works and blows air at the outside temperature, but I would like to have ac this coming summer instead of yet another year of rolled down windows ... So am I looking at needing a replacement ac clutch or what do you guys think?
Thanks a lot!
(This post was edited by eaglefan63 on Apr 30, 2010, 3:27 PM)
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nickwarner
Veteran
/ Moderator
Apr 28, 2010, 10:16 PM
Post #2 of 8
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Re: '91 Chevy S-10 AC issue
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first things first in an electrical problem is to test the electrical system. The connections must be clean and tight, battery testing out good along with alternator. Start there and this might be a real easy fix. Post back and we can take it to the next step if needed
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eaglefan63
New User
Apr 29, 2010, 4:40 PM
Post #3 of 8
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Re: '91 Chevy S-10 AC issue
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And the plot thickens...
Cleaned the connections and plugged the unit back up with no effect. The clutch didn't even try to engage, unlike last time when it pulled the engine down. Checked the wires leading to the unit and couldn't get a light, so we traced it back to the fuse box but the fuse checked out fine and the heater (which shares a fuse with the ac) still worked.
Suggestions?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 29, 2010, 6:34 PM
Post #4 of 8
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Re: '91 Chevy S-10 AC issue
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I think what may have happened is compressor was in process of seizing up dragging down idle which in turn the super low idle couldn't keep up the alternator and voltage. Now the system is out of refrigerant and won't even try to engage. Guessing of course.
If you took a pressure on the system you'll probably find a static pressure (just take pressure like you would a tire) lower than 40 or less PSI and you'll see an oily mess on front of compressor.
Take that pressure if you can, try to spin outer hub of compressor by hand (bet you can't) and let us know what happens and how far you want to go on your own with this depending on what you find,
T
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eaglefan63
New User
Apr 30, 2010, 3:03 PM
Post #5 of 8
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Re: '91 Chevy S-10 AC issue
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couldn't fit a tire pressure gauge one it, so I used the back of the pressure checker to let out some pressure to see if there would be any. didn't seem to be much of any pressure coming out of the unit. tried to turn the outside hub with my fingers and it actually turned fairly easily.
http://www.facebook.com/photo.php?pid=12228163&l=8beb876ebd&id=643785453
(checked the pressure at upper left corner, turned hub at bottom)
if we can figure out what it is that's wrong with it, my dad grew up fixing cars and my uncle next door is a retired mechanic so my first thought is if we can identify the problem, i can get it fixed.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 30, 2010, 7:49 PM
Post #6 of 8
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Re: '91 Chevy S-10 AC issue
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Sorry for confusion - I meant just take a static pressure for the system not use a tire gauge but one for A/C ACME fittings. It was just for info. Just sitting there, there should be a static pressure close to the ambient temp - the low side pressure port was in your picture with the blue cap on it. You need gauges for A/C fittings. Not sure what the other thing is - a vent for something.
The fact that out hub with three knobs turns by hand is indicative that A/C compressor isn't seized for now. Where I was going is drag of a burned out compressor was the issue and may not be at all. Pressure being too low if it was and I mean just static pressure not operating pressure would be information that if lower in PSI than ambient temp then when engaged the compressor would starve for oil already inside the system and could be dragging it down. DON'T ADD ANY REFRIGERANT - nothing is conclusive yet - just want to know if there's any pressure not if it's working properly yet.
So far I'm not even worried about whether A/C works or not just wanted to rule out it being the cause of your observations. Unplugging the two wire item on the silver canister in your picture is the low pressure cut out switch. While unplugged just there compressor won't work if it does drag down or stall engine when engaged leave it unplugged there or at the clutch to compressor itself.
Get some voltage readings also and at what RPM,
T
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eaglefan63
New User
Apr 30, 2010, 8:30 PM
Post #7 of 8
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Re: '91 Chevy S-10 AC issue
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so what do you make of the inoperative power supply? when we unplugged it, we did nothing other than pull it off the unit and wrap it in electrical tape to prevent it from grounding on the block. any clue as to why it's not supplying any power now (it connected on the prongs just above the outer hub cirlced at the bottom of the pic), since there were no obvious flaws in the wire leading from the fuse box and the fuse had a good reading?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 1, 2010, 1:57 AM
Post #8 of 8
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Re: '91 Chevy S-10 AC issue
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Is this to say now when you plug in compressor there's no power (voltage) present at that plug? That plug is to the clutch's coil, an electromagnet to pull in and engage compressor which will not get power unless LPCO (low pressure cut out) switch says pressure is within it's parameters. Generally it would allow (it's just an on/off switch by pressure) current while A/C is requested to pass thru, on to a relay and on to clutch.
If the coil was shorted at the compressor it should have blown a fuse I would think. Don't quote me but coil there should show about 2.5 to 4 ohms as measured from prongs from the coil at clutch.
Just key on engine off there should be power at one wire of the LPCO and if not chase that back to relay or fuse.
This all started with erratic idle and a bouncing amp/volt gauge triggered by requesting A/C. I'm not concentrating on whether the A/C works or not but it's role in causing the drag and jumping voltage. Nick suggested checking connections, GMs have issues with the side post battery connections but I would think the starter would be the first thing you would notice not working but they have to be known good.
Right now with clutch unplugged the whole A/C is just a pulley. Ducts and fan will work and if there's pressure, as said to LPCO there should be power as already said. I'm surprised if drain of current to clutch coil is enough to drag down the vehicle's voltage that much. Just a guess but it that voltage draw impeded power to fuel pump, ignition, injectors it would surprise me as plain headlights draw more I think and would have done it then.
For now, check and clean battery connections, check for blown fuses and take some plain voltage readings, engine off, engine at idle, raised idle and with headlights on at idle.
If you lack tools or testing equipment will it repeat what happened first if you plug it back in for just a second?
I can't tell yet if compressor itself is a problem or what but wouldn't leave one in question plugged in,
T
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