A/c "sweet Spot"

[nswst8]

Just wanted to hear from those who have done their own a/c work and have found that "sweet spot" to where your pressures are at their peak performance.

I just switched compressors, I had a Keihin (original compressor, converted to R134a in 1997 and just couldn't hold correct pressure any longer. Leak at the compressor suction port o-ring).

Bought a Denso kit off ebay last year and am glad that I did. Also bought a reman'ed keihin and that was worthless ( just a note to those that buy reman'ed off ebay, check it out immediately)

The Denso is operating wonderfully and would like to find the peak performance pressures. I know basics of tearing down, reassembling, vaccuming down and charging but since I can only use 12oz cans getting 20-22oz can be difficult.

[Dr_Snooz]

Ditto. If anyone knows what the head pressures should be, I'd appreciate it as well. Mine sprang a leak and I need to recharge, but don't trust the two cans method.

[Oldblueaccord]

I'm thinking 40 225 maybe is where you want to be with R-134a.

wish i had guages i would tell you mines running sweet this year.

[nswst8]

I'm at 35 low / 270 high and its cooling down to 42-45 degrees at the center vent 95 outside temp.

[nswst8]

Another question for you A/C experts, "PLEASE HELP" car idles fine w/o a/c running. when I have the A/C running the car idles low after coming to a stop. book says 1) IAC 2) A/C signal

How do I clean, check IAC?

What is the experience on the board with this issue?

Thanks all,

[nswst8]

Bump

[ecogabriel]

Hello,

I have just fixed the same problem in my '86LXi a couple of days ago.

Look at the Accord manual(it can be downloaded from this site somewhere).There is a "vacuum and electrical connections diagram" in page 12-7. Take a look at the diagram; it will help you navigate the maze of hoses and direct you to where you should go.
I found out that the low idle when A/C running (in my case) was due to an inoperative "A/C idle boost solenoid valve" (#18 in the diagram). That solenoid is energized when the compressor is ON and opens the "A/C idle boost valve" (#19 in the diagram) by directing engine vacuum to open the valve. The solenoid is operated by the ECU itself (I think)

The A/C idle boost valve is located in the intake manifold towards the right end of it (looking the engine bay from the front of the car. To test it unplug the hose #19 and connect a vacuum pump; with the engine running apply vacuum to it -idle speed should increase and hold vacuum. Mine was OK so I tracked back the hose to the control box where the solenoid is located.

The A/C idle boost solenoid may be tested for continuity but you need to open the control box in order to test/replace it. Assuming the box is already opened, set a tester in the ohms scale and check for continuity between the electrical contacts of the solenoid. If it is good you should see some value close to 0. Mine was fried, but nevertheless I checked whether it received voltage. Set the tester in DC volts and measure the wires with the A/C on and key in the contact position -you should read about 12V in those wires.

In order to get a working valve I went to the junkyard and hunt for one. The solenoid may be found in either a carbureted or a fuel injected control box -there is another solenoid valve that is similar that is used for some distributor advance function. You must have a tester with you to see whether the solenoid works; several solenoids I checked for continuity were dead The ones that tested good worked when I tried in the car back home (I bought two at about $6 a piece). Alternatively, you may check with a 12v battery; applying voltage to the contacts will make the solenoid "click".

Similarly, if your problem is in the boost valve you may need a vacuum pump to see whether it holds vacuum in the port where the #19 hose connects to; that is the port that the solenoid allows vacuum when needed

Finally, you may need to recalibrate the idle boost valve for optimal idle speed; there is a screw in the lower part of it that plays that role.

Hope it helps.

[ecogabriel]

One correction: my car's problem was that every time I turned on the A/C the idle speed was lower than when it was off (the engine vibrated quite a bit with A/C on as a result of the lower idle speed + load applied to the engine.

Overall, my previous posting applies. I would first check that the idle boost valve works before doing anything else.

Good luck

[Oldblueaccord]

good write up there ^^^^ could just boost the overall idle up just a little as well. If your getting 270 head pressure that maybe dragging the motor down a little more the Honda engineered into there system.

[rapnap1]

Hello,

I have just fixed the same problem in my '86LXi a couple of days ago.

Look at the Accord manual(it can be downloaded from this site somewhere).There is a "vacuum and electrical connections diagram" in page 12-7. Take a look at the diagram; it will help you navigate the maze of hoses and direct you to where you should go.
I found out that the low idle when A/C running (in my case) was due to an inoperative "A/C idle boost solenoid valve" (#18 in the diagram). That solenoid is energized when the compressor is ON and opens the "A/C idle boost valve" (#19 in the diagram) by directing engine vacuum to open the valve. The solenoid is operated by the ECU itself (I think)

The A/C idle boost valve is located in the intake manifold towards the right end of it (looking the engine bay from the front of the car. To test it unplug the hose #19 and connect a vacuum pump; with the engine running apply vacuum to it -idle speed should increase and hold vacuum. Mine was OK so I tracked back the hose to the control box where the solenoid is located.

The A/C idle boost solenoid may be tested for continuity but you need to open the control box in order to test/replace it. Assuming the box is already opened, set a tester in the ohms scale and check for continuity between the electrical contacts of the solenoid. If it is good you should see some value close to 0. Mine was fried, but nevertheless I checked whether it received voltage. Set the tester in DC volts and measure the wires with the A/C on and key in the contact position -you should read about 12V in those wires.

In order to get a working valve I went to the junkyard and hunt for one. The solenoid may be found in either a carbureted or a fuel injected control box -there is another solenoid valve that is similar that is used for some distributor advance function. You must have a tester with you to see whether the solenoid works; several solenoids I checked for continuity were dead The ones that tested good worked when I tried in the car back home (I bought two at about $6 a piece). Alternatively, you may check with a 12v battery; applying voltage to the contacts will make the solenoid "click".

Similarly, if your problem is in the boost valve you may need a vacuum pump to see whether it holds vacuum in the port where the #19 hose connects to; that is the port that the solenoid allows vacuum when needed

Finally, you may need to recalibrate the idle boost valve for optimal idle speed; there is a screw in the lower part of it that plays that role.

Hope it helps.

I verified that indeed, it is NOT my AC Idle Boost Valve, but the A/C Idle Boost Solenoid Valve would not hold vacuum as per the instructions in the original manual for the test. Question is where does one get this part besides the junkyard, and is it a fact that you can use the Solenoid Valve from a Carburetor engine as well? I have Fuel Injection 1986 LXi. Dealerships know nothing about this, but know they can't get the part, so they tell you they will have to charge you over $100 for diagnostics, and then the bad news, they can't get the part.

Your post was extremely helpful to me, in a problem I've lived with for years, and no mechanic could find the problem. If you still have working ones, how much to ship to Arizona for one? Again thanks for your great post.

[gp02a0083]

good call on the compressor change, the keihin compressors really don't take well to the R-134A conversion. Some here have had some success, however after researching on the forum its really a "ticking time bomb" as the frint seal typically gives out.

High and low side pressures will vary depending on the ambient temperature and %RH, but going by ambient temperature alone will work fine. Here are two charts to help:



I forget what the correct percentage adjustment is needed to compensate for the R-134A conversion and required ounces of oil. I'll have to see what I have in my notes when I get home.
The issue regarding the size of the cans using the complete amount is a little tricky and as you and have implied, there is some excess freon left over anytime i have done a complete discharge / charge up. Some cans come in 14-16oz's as well, but they typically have stop leak additives and other garbage in them.

[Vanilla Sky]

I'm going to stick this post in the FAQs.