AC doesn’t start when AC button pressed (engine revs too low) (1 Viewer)

[t00manyuserz]

Having a curious issue with my idle speed.

- regular idle is around 650 rpm, as per FSM
- pressing the AC button moves idle to about 750-800 rpm, which is about right
- but … AC does not start. It wants around 1,000 rpm. So if i press the gas, a relay in the passenger footwell clicks and the AC starts (and works fine), or if I use the throttle choke cable. If I hold the revs it works fine. If I release the gas, it’ll run for a little bit then switch off (and it gets hot). AC thermostat is set to 20C.

This is on a 1994 1FZ-F (carburated) if that makes any difference.

Is there anything I can adjust?

 

[Malleus]

The A/C doesn't rely on the engine rpm, it adjusts it. Something else is going on.

 

[t00manyuserz]

The A/C doesn't rely on the engine rpm, it adjusts it. Something else is going on.

What I mean is, the AC comes on at a certain engine rpm, not below, and turning on the AC boosts the engine throttle to reach that rpm that the AC considers "safe" to run at (so as not to stall the engine, I guess). Except in my case it doesn't boost it to the point where it turns on, hence my issue. I don't feel like anything is broken, though - I think I need to adjust something.

I am wondering if I need to adjust the thing that sits on the front side of the carburetor. In the 1FZ-F Engine PDF off the resources section, page EG-30, it mentions a "fast idle speed" which should be 800-1,000 for GCC - mine is 800, so I think I should raise it, but I am not sure if that is what I should be adjusting or not. Except I don't really understand that section at all (what's a fast idle cam setting at 4th step? lol).

 

[Malleus]

The A/C is responsible for setting the idle, independent of the fast idle setting, which is for warmup.
For some reason, my copy of the 1994 FSM doesn't include a section for A/C; this is from the 1995 FSM:

So, number 1 on the list is check the drive belt tension. Numbers 2 & 3 are refrigerant level check. Numbers 5 & 6 a re compressor checks.

There is an engine control check: voltage between A/C and E1 terminals on the ECU should be between 7.5-14 VDC when the A/C switch is ON.

 

[Malleus]

In case it isn't clear, the diagram identifies the ECU terminals as you look at them, from the point of view of the cables going into the ECU connectors. You need to insert the probe into the rear of the ECU connector of the harness. The ECU has to be plugged into the harness to make these tests.

HTH; that's all I got

 

[t00manyuserz]

Thanks. I'll check the voltage. I had the refrigerant flushed not long ago and even before I did, it was correctly pressurised, so it's probably not that... and what's confusing me is that it's absolutely 100% consistent with the required rpms - exactly 1,000, which is what was making me think there's an adjustment valve somewhere (after all, when I hit the AC button, it pulls the throttle somewhere, right? I was thinking I can adjust by how much it pulls that).

 

[Malleus]

So, if you're sure the drive belt tension is correct, it looks like you're down to a faulty compressor.

The Kriket does the same thing for waaay less than either of the two in the FSM

 

[BILT4ME]

So, if you're sure the drive belt tension is correct, it looks like you're down to a faulty compressor.
View attachment 3350576

The Kriket does the same thing for waaay less than either of the two in the FSM
View attachment 3350577


View attachment 3350579

View attachment 3350580

Remember, though, he is carbureted, not fuel injected.

So, there must be a dashpot or solenoid that bumps the linkage on the carb to boost the RPM.

I am NOT familiar with these in a carb'ed version, but that's from my other carb experience.

OP: Look for a vacuum hose that is disconnected or leaking around or near the carb. It may not be able to generate enough vacuum until you increase the RPM on the engine.

 

[Malleus]

Well, I missed that totally

 

[t00manyuserz]

Well, I missed that totally

Hehe no worries, I felt like those may still apply, but in the end yeah, I feel like it's going to boil down to a cable that some vacuum hose pulls that just needs to be adjusted by a millimetre or so, just can't figure out which. And of course nobody has a carbureted car anywhere, so I've nobody to ask

 

[TomH]

This is what @BILT4ME is talking about. Not sure this if this is the AC control. The picture is of your motor.

 

[t00manyuserz]

This is what @BILT4ME is talking about. Not sure this if this is the AC control. The picture is of your motor.

View attachment 3351215

Yep I think that must be it, but I can’t find any explanation what to do with it anywhere

 

[TomH]

So again, I'm not sure that is the AC adjustment but it is some type of vacuum controlled carburetor adjustment. First thing you should do is check the vacuum hoses and see if they are tight. If the lines are good then you might just want to throw parts at it.

Looking at the parts diagram the red circled thing is part of the carb and probably not available separately. The blue thing is called a vacuum transmitting valve and could be your problem. It looks like it then goes into the yellow circled part which is a gas filter.

 

[t00manyuserz]

Ok, I see what you're saying. The red thing does seem to be part of the carb, but that's OK because I actually replaced the whole carb a couple of months ago, and anything around there is brand new. But this filter thing - indeed, that is old, and I wonder if that may be it, rather than an adjustment?

I am seeing two of these "Qalve" things, one in front, and one in the back. They seem to be around $10-15 each so I think I should replace both and that filter thing, and see whether that helps.

Front one:

Rear one:

 

[BILT4ME]

Ok, I see what you're saying. The red thing does seem to be part of the carb, but that's OK because I actually replaced the whole carb a couple of months ago, and anything around there is brand new. But this filter thing - indeed, that is old, and I wonder if that may be it, rather than an adjustment?

I am seeing two of these "Qalve" things, one in front, and one in the back. They seem to be around $10-15 each so I think I should replace both and that filter thing, and see whether that helps.

Front one:
View attachment 3351627

Rear one:
View attachment 3351628

Are they installed the correct direction?

 

[t00manyuserz]

Are they installed the correct direction?

I'm not sure there's more than one way to install them? Seems OK to me though, at least, they are both installed with the same face facing up.

And I feel like if they weren't, something more vile would be afoot, such as the AC not turning on and so on, wouldn't it? As opposed to being about 200rpm short. Or maybe I don't really understand how they work.

 

[Bardiya]

On 1FZ Carb models there is an A/C Amplifier with RPM adjustment screw under the dash.

The amplifier looks like this:

80 Series 1FZ-F Dual A/C Amplifier Assembly

Amplifier Assembly for Carbureted 1FZ-F FZJ80’s 88650-60170 077100-4900 12V 1FZ-D

jumeirahparts.com

 

[t00manyuserz]

On 1FZ Carb models there is an A/C Amplifier with RPM adjustment screw under the dash.

The amplifier looks like this:

80 Series 1FZ-F Dual A/C Amplifier Assembly

Amplifier Assembly for Carbureted 1FZ-F FZJ80’s 88650-60170 077100-4900 12V 1FZ-D

jumeirahparts.com

Eh really? Any idea where it might be? Searching the part #, it does seem like my car might have it.

 

[Bardiya]

Eh really? Any idea where it might be? Searching the part #, it does seem like my car might have it.

It's bolted onto the Evaporator box

 

[BILT4ME]

I'm not sure there's more than one way to install them? Seems OK to me though, at least, they are both installed with the same face facing up.

And I feel like if they weren't, something more vile would be afoot, such as the AC not turning on and so on, wouldn't it? As opposed to being about 200rpm short. Or maybe I don't really understand how they work.

They're more along the line of a check valve. If installed backwards, they may not flow in the direction needed.

Just speculation.