Engage A/C compressor clutch

Hello,
I replaced an A/C suction hose on a 2002 Tundra. Following instructions on the can of R-134, I put in the refrigerant until I had 25 pounds, but I noticed that the compressor clutch had not engaged. I removed the heater relay next to the battery, thinking I could put a jumper to engage the compressor clutch, but there is not a wiring schematic on the relay, and the 5 relay pins are not numbered.
I then thought I could put 12V right at the compressor clutch. I can pull the electrical connection apart at the compressor, but the side I would need to run a jumper to is secured to a bracket that I cannot separate from the plastic retaining piece. I can imagine breaking the brittle plastic, so abandoned this plan.
At this point I am back to running a jumper at the heater relay. Would someone know how to do this, or have another plan?

Ken

 

FYI you need to vacuum the system before adding the refrigerant. Did you do so?

And did you have the engine running and A/C on max when you started adding? Sometimes they don't initially trigger until 35+ psi.

 

Assassin 10000, The suction hose had been chewed on by a rodent. They refrigerant had totally leaked out, but to answer your question I did not vacuum the system. I did have the engine running and the A/C on max, following the instructions for the refrigerant.
Thanks,
Ken

 

Gotcha.


I'd add a full can first to see if it'll start working.

You could try bypassing the pressure sensor to see if it'll cycle. I'd also check the wiring, perhaps one of the AC wires got chewed on too.

 

Air/non condensables will create high head pressure and not good for the overall system

 

If you still need to jumper HTR relay contacts, pin 1 and 2 would be the contacts of the relay.

 

I do not own a vacuum pump, and have never needed one when re-filling an opened AC.

What I do is simply purge the system with coolant, by hooking up a bottle on the low pressure side, and holding down the valve on the high pressure side for 10 seconds or until I visibly see coolant coming out. Its always worked for me.

On some vehicles you can just re-charge the system, on some you have to jump the compressor to get it to start working.

 

Hello again,
All of these ideas are great. I appreciate the input. This gives me a lot to work with.
Thank you,
Ken

 

Hello again,
I purchased a vacuum pump and manifold gauge set. After injecting 1 12 ounce can of R134a, the a/c blew cold. The compressor clutch is cycling about every 15 secs. at 1500RPM's The high pressure is ranging from about 75-125# and the low pressure is ranging about 20-40. Should I add more refrigerant? Should the compressor cycle this often? My concern is adding too much refrigerant.
Thanks,
Ken

 

The truck has a sticker with how much to put in, it sounds like you need to add more

 

^ This. 16-20 oz or something like that.

Iirc the rule of thumb is ambient temp multiplied by about 2-2.5x = high side pressure.

 

I did not have a scale to weigh what amount of refrigerant I used. I will buy a scale for next time.
Today I tried the 2-2.5 high side pressure. It was 60 degrees in N. Calif. The high pressure read 150,# dropping to 130# and the compressor would cycle every 15-20 secs. as it had been doing. Today I added refrigerant to raise the high side pressure to 160# but the readings continued to fluctuate, and the compressor would cycle. The A/C does blow cold, it is the cycling that is the problem. I do not remember the cycling before I replaced the suction hose.
Last week when I had the vacuum pump on the system after replacing the hose, the vacuum dropped to 30 in a few seconds. I ran the pump for about only 5 minutes, shut it off and the vacuum reading held.
Thank you for any ideas.
Ken

 

Well, cycling is normal, thats how its supposed to work. 12-20 seconds sounds faster than normal, but it completely depends on the how well the AC is working, and how much it has to work, faster cycling when its cool, longer cycling or even no cycling when its hot (if it can't ever drop the pressure because its not keeping up, it never cycles off)

I'd run mine to compare, but its 22º here so probably not a good comparison.

 

What was the low side?

 

assassin 10000, The low pressure ranged about 20-40# at 60 degrees outside temperature.
Ken

 

@Westmoor63
For folks to know you are responding to them, add an @ to their name.... @assassin10000 ....they'll then get an alert !

 

Might be a hair low, but splitting hairs at this point. Assuming turning off at 150/20psi and back on at 40psi.

I'd wait until ambient temps rise a bit (75-90) and check again.

 

@assassin10000,
I will check again when weather warms up.
I appreciate your help.
Ken

 

Have you found the sticker on the front support with the oz weight for the freon?
You don’t necessarily need a scale……. Maybe a coffee scale if your feeling fancy, just get two cans and use all of the first and most of the second as close as you think you are to proper weight.
Also, I always run my vacuum pump for a minimum of 30 minutes, the longer the better. (I also triple evacuate, but that’s for a different day) also make sure you purge your charge hose with freon slightly, before you open the valve to let gas in.

 

@FrenchToasty,
If the cycling does not settle down when the weather warms up, I will have the refrigerant evacuated, run my vacuum pump for at least 30 minutes and be more accurate with the amount of freon I put in the system.
At least I did purge the charge hose at the gauges before adding gas.
Thank you for the advice,
Ken

 

@FrenchToasty,
The A/C sticker reads 1.43# Max., 1.21# Min.

 

So you basically need two full cans in the system, maybe a long purge on your hose and suck in both cans. (12oz cans)

 

The high pressure hose will probably have the extra .12oz lol.

 

Hahah I never hook up the high side.