93 Toyota Pickup ac
The ac on my truck works perfectly fine until you stop and sit still for a couple of minutes the compressor starts cycling on and off rapidly but when you start moving it works fine. It also cycles on and off when you crank it after it has warmed up. Any help or advice is appreciated
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Will it stop cycling if you ever-so-slightly raise the rpm? There may be a control labeled "rpm" on the A/C "amplifier" located on top of the Cooling Unit. I'm not 100% clear on its use (it is not well documented). But I think it adjusts a minimum engine rpm, below which the A/C won't run. You could try that.
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Originally Posted by scope103
(Post 52425634)
Will it stop cycling if you ever-so-slightly raise the rpm? There may be a control labeled "rpm" on the A/C "amplifier" located on top of the Cooling Unit. I'm not 100% clear on its use (it is not well documented). But I think it adjusts a minimum engine rpm, below which the A/C won't run. You could try that.
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Originally Posted by Jooosshua
(Post 52425627)
The ac on my truck works perfectly fine until you stop and sit still for a couple of minutes the compressor starts cycling on and off rapidly but when you start moving it works fine. It also cycles on and off when you crank it after it has warmed up. Any help or advice is appreciated
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Originally Posted by yota tay
(Post 52425637)
I'm pretty sure thats normal operation. How do you expect the condenser to dissipate heat without airflow? Far as I can tell there's only the clutch fan for pulling air across the coils at a stop, and that isn't big or strong enough in stock form for cooling duties at a stop. Add a condenser fan motor and you will be happy.
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Does anybody have a link on how to correctly adjust this amplifier? I turned mine accidentally without making note of where it was set at.
Edit: played with the amplifier, basically it changes the idle when AC is on. Adjuster can increase/decrease about 250rpms. I put mine at lowest setting, idle now sits at 1000rpm when AC is on. Fully counter clockwise puts idle at about 1250rpm. Have to recycle AC switch to see result of adjustment, just turning knob while AC is on does nothing until main switch is recycled. |
Tried adjusting the amplifier and it’s at its lowest setting but when the vehicle stops and idles the compressor cycles on and off rapidly still. I have no other ideas
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Low pressure switch shuts off compressor. Your pressure is good?
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What type of refrigerant is in the system?
Has the refrigerant ever been changed to a different type than what was originally in the Truck? Is the A/C system properly charged? :safari: |
The system has been converted to 134a was r12 originally, but it is charged correctly and the pressures are reading right. I vacuumed the whole system and it held vacuum.
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Here is a video of the idling
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I can’t seem to get the video to upload, I can email or send the video however if anyone wants to see how it idles
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Here is the FSM for 89-95s. Since it sounds like the compressor is losing it's voltage signal I would check the operation of the thermisitor, pressure switch, amplifier & relay. All you need is a multimeter. FSM requires a manifold gauge set to test the pressure switch, but it can be easily bypassed to see if that is the issue. Bridge the 2 contacts in the plug for continuity. If compressor runs fine with pressure switch out of the equation, you have low pressure or a bad switch. I have a few pics from the '87 FSM I can post to test these components:
https://ether3al.com/93fsm-mobile/airconditioning.html |
Originally Posted by Paul22RE
(Post 52425878)
Here is the FSM for 89-95s. Since it sounds like the compressor is losing it's voltage signal I would check the operation of the thermisitor, pressure switch, amplifier & relay. All you need is a multimeter. FSM requires a manifold gauge set to test the pressure switch, but it can be easily bypassed to see if that is the issue. Bridge the 2 contacts in the plug for continuity. If compressor runs fine with pressure switch out of the equation, you have low pressure or a bad switch. I have a few pics from the '87 FSM I can post to test these components:
https://ether3al.com/93fsm-mobile/airconditioning.html |
Originally Posted by Jooosshua
(Post 52425887)
Do I need to unplug the switch or just probe into the connector? Those seem like some high pressures.
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Originally Posted by Paul22RE
(Post 52425896)
Unplug the electrical connector to the switch, bridge the two contacts in the plug (on the wire side, not the switch side). Turn AC on and see if compressor stays on. What year is your truck? 22RE I assume? Pre-89 it is called a low pressure switch, 89-on it is called a dual pressure switch. Or better yet if you can probe it while connected, you could see if it's cycling on and off with the AC running. Any chance your pressure might be too high?
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High pressure could be a few things:
Overcharged (too much refrigerant) Too much oil in the system Wrong oil in the system Debris in the system Clogged dryer Crimped line Bad expansion valve Air contamination in system Water contamination in system Poor airflow over condenser Dirty condenser coils |
Originally Posted by Paul22RE
(Post 52425910)
High pressure could be a few things:
Overcharged (too much refrigerant) Too much oil in the system Wrong oil in the system Debris in the system Clogged dryer Crimped line Bad expansion valve Air contamination in system Water contamination in system Poor airflow over condenser Dirty condenser coils |
FSM is here, click on "Cooling Unit" in this link: https://ether3al.com/93fsm-mobile/airconditioning.html
When I changed the heater core in my 92 I also wanted to clean up the evaporator without disconnecting the lines. The box seemed tricky to get off so just cleaned each side of the evaporator by removing the blower motor assembly on one side and had heater core out on other side. I did not see an easy way to get that box off of a connected evaporator. Why do you want to take the box apart? Maybe someone else here can chime in on how/if they got the box apart without disconnecting the lines? |
I have seen here in the past when these R12 systems get charged with R134A, you can get similar symptoms as you are getting.
It may be possible that there just isn't enough air flow going through the condenser at an idle to make the A/C system happy with R134A, but that is just a guess. I don't have A/C in my truck, so I am just passing along what I have seen on this forum. :safari: |
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