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Have a 79 L82 coupe, which I had in the shop having the A/C system brought up to modern standards. Prior to taking it in.......due to a "leak" the compressor would not engage...however the "on switch" DID send a signal to the carburetor that made the RPMS increase.
Now that I have the car back from the shop, I find that the A/C works fine, albeit a bit weak on the blower output...but that is for a different time .......the PROBLEM is when I am stopped at a traffic light, just for example, with the A/C on,,,the idle gradually drifts down until it eventually stalls the motor.....or course making it a real PITA to get restarted.
Apparently the "switch" or whatever it is, that causes the idle speed to INCREASE when the A/C is on, is not functioning.
Sorry for the lengthy introduction.....but I would like to know it is something simple that I can do to remedy this problem....as I have contacted the shop that DID the work, but no one has called me back. I guess that's typical nowadays.
Should be a wire on the end that connects check and see if either end was knocked off. Check vacuum hoses to see if any of those are disconnected for some reason.
Should be a wire on the end that connects check and see if either end was knocked off. Check vacuum hoses to see if any of those are disconnected for some reason.
Jeez but I hate to sound dumber than I actually am...but I hafta ask, "wire on the end of WHAT"........"that connects TO what"? I went and checked on the vacuum hoses.......all seem ok. I did notice that on the drivers side of the carb is what I might call a "dashpot"....at least that's what it LOOKS like from my really old skool knowledge of such things. Is THIS the thing this is supposed to keep the engine from stalling like it is doing, or is it something else I need to check?
Jeez but I hate to sound dumber than I actually am...but I hafta ask, "wire on the end of WHAT"........"that connects TO what"? I went and checked on the vacuum hoses.......all seem ok. I did notice that on the drivers side of the carb is what I might call a "dashpot"....at least that's what it LOOKS like from my really old skool knowledge of such things. Is THIS the thing this is supposed to keep the engine from stalling like it is doing, or is it something else I need to check?
sounds like it...obviously you have an automatic because i have 79 l82 and the manual has no kick up..and idle is 900 rpm..
send a pic of what you are looking at
Last edited by interpon; Sep 17, 2020 at 06:14 PM.
Jeez but I hate to sound dumber than I actually am...but I hafta ask, "wire on the end of WHAT"........"that connects TO what"? I went and checked on the vacuum hoses.......all seem ok. I did notice that on the drivers side of the carb is what I might call a "dashpot"....at least that's what it LOOKS like from my really old skool knowledge of such things. Is THIS the thing this is supposed to keep the engine from stalling like it is doing, or is it something else I need to check?
What you are looking at is the fast idle solenoid. It should be energized when the A/C is on, or rather when the compressor clutch is engaged. Watch what it does when the A/C is on. You should see the plunger extend out of the body of the solenoid, raising the idle speed. If it doesn't do that, check the wiring to make sure everything is connected, no broken wires, etc. If it does, but not enough, you need to take a wrench and turn the plunger out to extend it and raise the idle speed. Hope that's reasonably clear.
Here is a picture of what mine looks like (1979 and this all functions)... so, the wire that goes to the compressor at the top engages the clutch. At the same time, the solenoid at the bottom energizes, and plunger goes against the throttle linkage to increase the idle.
I also converted to 134A last summer, new dryer, rubber lines, orifice tube, and replaced all the o rings. Still has the r12 compressor, and still blows cold.
What you are looking at is the fast idle solenoid. It should be energized when the A/C is on, or rather when the compressor clutch is engaged. Watch what it does when the A/C is on. You should see the plunger extend out of the body of the solenoid, raising the idle speed. If it doesn't do that, check the wiring to make sure everything is connected, no broken wires, etc. If it does, but not enough, you need to take a wrench and turn the plunger out to extend it and raise the idle speed. Hope that's reasonably clear.
Absolutely clear...thank you so much. I will, in the morning, go out and check on whether this fast idle solenoid does indeed have attached wiring. I am more familiar with AFB carbs than I am with QuadraJets.,,,and THAT was some 50 yrs ago. I have now since learned that the shop also put a "kit" in the quad carb, supposedly to cure a bad accelerator pump. It was noted on the bill...I just overlooked it. One would THINK that the mechanic would have had the sense to check this out before turning the car loose to the customer. Oh well.
I checked on the Vette this morning and what I thought looked like a dashpot, was indeed a "fast idle solenoid". It was wired correctly, but not EVEN close to being adjusted properly.
NOW the engine continues to run while the A/C is on and car is stopped and in gear. Goes from around 900 rpm in neutral, to about 600 rpm in gear and drops to 500 rpm when A/C is turned on and compressor clutch engages. Does that sound about right?
Thanks much for all the helpful hints suggestions and ideas as to how to resolve this problem.....couldn't have done it without ya.
On another "side note", I have noticed that there is a rather pronounced "lope" in the idle.....not extreme, but not necessarily smooth either. Does an L82 have such a long duration cam, or am I now looking at adjusting the air/fuel mixture as well? It could it be the previous owner had a bigger cam installed and simply didn't mention it when I bought the car? Cannot reach him any longer, so cannot ask. Just curious. The Vette does run good however....not a tire-burner, but does manage to keep up with traffic.
Last edited by TuffShift; Sep 18, 2020 at 12:19 PM.
I checked on the Vette this morning and what I thought looked like a dashpot, was indeed a "fast idle solenoid". It was wired correctly, but not EVEN close to being adjusted properly.
NOW the engine continues to run while the A/C is on and car is stopped and in gear. Goes from around 900 rpm in neutral, to about 600 rpm in gear and drops to 500 rpm when A/C is turned on and compressor clutch engages. Does that sound about right?
Thanks much for all the helpful hints suggestions and ideas as to how to resolve this problem.....couldn't have done it without ya.
On another "side note", I have noticed that there is a rather pronounced "lope" in the idle.....not extreme, but not necessarily smooth either. Does an L82 have such a long duration cam, or am I now looking at adjusting the air/fuel mixture as well? It could it be the previous owner had a bigger cam installed and simply didn't mention it when I bought the car? Cannot reach him any longer, so cannot ask. Just curious. The Vette does run good however....not a tire-burner, but does manage to keep up with traffic.
I adjust mine to bring the idle up to the same as without the A/C on. Seems to work for me. Bottom line is feel free to play with it until you come up with something that feels right to you.
And yes the L82 cam will have a bit of a lope to it. Its P/N 3896962 - funny how some things like that just stay in your head for years, and yet I can't remember my own phone number. I had one in a 350 Monza. Duration is about 222/222 @ .050" and lift around .450 which is a lot more than the base camshaft. The problem was the engine didn't have enough compression to use that much camshaft so the engine just didn't live up to the potential of the camshaft. If you can raise the compression to around 10:1 it really wakes it up.
I adjust mine to bring the idle up to the same as without the A/C on. Seems to work for me. Bottom line is feel free to play with it until you come up with something that feels right to you.
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Well guess what?.......was supposed to up in the upper 80's low 90's today and tomorrow.....figured it would be a good time to take the NOW Air-Conditioned Vette out for a drive. Only one small problem. No cold air coming from the vents. Pulled over, lifted the hood and 'voila', the compressor clutch is not engaging. Monday morning the C3 is going BACK to the shop, with the caveat to NOT tell me it is "finished" until it is THOROUGHLY road tested...AND that there are no "leaks" in the AC lines (which is what I assume is the problem).
This C3 came with a short piece of "rope" beneath the drivers seat......I think I know what it was there for.....obviously, it WAS the previous owners' rope, and he REACHED the end of the rope and got rid of the Vette.. I can feel his frustration, as I am getting close to the end of MY rope, too.
Last edited by TuffShift; Sep 25, 2020 at 11:43 PM.
Already a problem with rebuilt A/C
.......the PROBLEM is when I am stopped at a traffic light, just for example, with the A/C on,,,the idle gradually drifts down until it eventually stalls the motor.....or course making it a real PITA to get restarted.
