do you have the EWD?
next step is to figure out witch one of the relays is cycling the compressor off.
next step is to figure out witch one of the relays is cycling the compressor off.
2/93 A/C Mystery - Need Ideas and Help
- Thread starter Gieser
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- Thread starter
- #42
Electrical Wiring Diagram
I take that as a no?
I take that as a no?
Does the evaporator have a freeze switch? It might be defective and turning off the compressor too soon.
yes there is a thermistor
also if the coolant gets too hot (as measured at the head) the compressor will be cut out by a realy,
there is a good old thread about this last one what just got bumped and is active right now.
also if the coolant gets too hot (as measured at the head) the compressor will be cut out by a realy,
there is a good old thread about this last one what just got bumped and is active right now.
I remember some discussions of how often the compressor is cycling.
I also have the cooling / compressor cycle on and off at a frequency of about 1 minute or so. And there is a clear correlation between the clicking and the stoppage / resumption of cooling.
I had assumed the cycling is normal but maybe it's not, then...
Do most of you have the compressor stay on all the time?
I also have the cooling / compressor cycle on and off at a frequency of about 1 minute or so. And there is a clear correlation between the clicking and the stoppage / resumption of cooling.
I had assumed the cycling is normal but maybe it's not, then...
Do most of you have the compressor stay on all the time?
mine cycles in the winter when defrost is used, stays on in the summer.
- Thread starter
- #48
I do have this.
I saw the post on this and thought it could relate to my problem. I spent about an hour on it and then checked my cruiser. Even though my compressor is switching on and off, when it does stay on continuously, which it does when it wants to, it still will not cool below about 60 degrees.
I thought about this as well, but I did not see that it would be the solution for the cooling problem, but possiby for the compressor on/off issue.
- Thread starter
- #49
Okay, we have the issue of the air not getting cold enough (even though all parts replaced and flushed, etc. etc) which is really now a mystery except for the possibilites of it being the AMP, sensors or switches. 
We also have the problem of the A/C kicking on/then off, etc. This is not happening all the time, but sometimes. Still, when the compressor decides to run consistantly, it still cools at 65 degrees or 70 degrees, etc. When I start the car in really hot weather (like today), the compressor will not even kick on for a bit.
Through diagnostics, we have excluded any blockage, any bad parts in the A/C line (Compressor, Clutch, receiver, expansion valve, evaporator, condenser), amount of freon, amount of air flow through condenser (fan clutch), heat valve, temp adjustment setting. The guages read fine and the temp of coolant is perfect.
To me, tis leaves a relay, a switch, a sensor, or something like that. What do you think?
We also have the problem of the A/C kicking on/then off, etc. This is not happening all the time, but sometimes. Still, when the compressor decides to run consistantly, it still cools at 65 degrees or 70 degrees, etc. When I start the car in really hot weather (like today), the compressor will not even kick on for a bit.
Through diagnostics, we have excluded any blockage, any bad parts in the A/C line (Compressor, Clutch, receiver, expansion valve, evaporator, condenser), amount of freon, amount of air flow through condenser (fan clutch), heat valve, temp adjustment setting. The guages read fine and the temp of coolant is perfect.
To me, tis leaves a relay, a switch, a sensor, or something like that. What do you think?
just looked at mine for the cycling issue.
Observations: only cycled off when the temp dropped below 49F at the outlet. (The 49F is likely not an absolute number and would likely vary depending on conditions). Practically, this meant it cycled a lot (every 15secs or so) between 49F and 51F or so when the fan was on low. It never cycled when the fan was on high. At intermediate fan speeds it cycled or not "depending" on the outlet air temp. This is at idle in the garage with air outside about 70F.
I removed the A/C coolant temp sensor connector. Did not affect the cycling.
So, it is either:
- pressures off in system
- pressure switch bad (when I disconnected it, A/C didn't work, as expected)
- evaporator thermistor bad.
- amplifier, relays etc
- normal
Observations: only cycled off when the temp dropped below 49F at the outlet. (The 49F is likely not an absolute number and would likely vary depending on conditions). Practically, this meant it cycled a lot (every 15secs or so) between 49F and 51F or so when the fan was on low. It never cycled when the fan was on high. At intermediate fan speeds it cycled or not "depending" on the outlet air temp. This is at idle in the garage with air outside about 70F.
I removed the A/C coolant temp sensor connector. Did not affect the cycling.
So, it is either:
- pressures off in system
- pressure switch bad (when I disconnected it, A/C didn't work, as expected)
- evaporator thermistor bad.
- amplifier, relays etc
- normal
FJ809496TLC
80 series addict
Gieser said:
- Thread starter
- #52
We changed the generic fan clutch to a Toyota fan clutch and it made a world of difference. Actually we tried 3 generic fan clutches and none of them were worth anything.
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Gieser said:Okay, we have the issue of the air not getting cold enough (even though all parts replaced and flushed, etc. etc) which is really now a mystery except for the possibilites of it being the AMP, sensors or switches.
We also have the problem of the A/C kicking on/then off, etc. This is not happening all the time, but sometimes. Still, when the compressor decides to run consistantly, it still cools at 65 degrees or 70 degrees, etc. When I start the car in really hot weather (like today), the compressor will not even kick on for a bit.
Through diagnostics, we have excluded any blockage, any bad parts in the A/C line (Compressor, Clutch, receiver, expansion valve, evaporator, condenser), amount of freon, amount of air flow through condenser (fan clutch), heat valve, temp adjustment setting. The guages read fine and the temp of coolant is perfect.
To me, tis leaves a relay, a switch, a sensor, or something like that. What do you think?
Try unplugging the compressor clutch and jumpering it to hot (12v +) so it stays on all of the time, then run a max A/C test. Be careful, you will have no safeties like hi pressure switch, best done with gauges hooked up and monitored. This will tell if the A/C system is capable of putting out cold air, if it passes move on to the electric controls.
With your symptoms the first thing I would check is the thermistor and it's wiring. Some of them are just in the evaporator box, some clip to a line close to the evaporator and some shove in to the fins of the evaporator. When you changed the evaporator was it reinstalled with good contact to the line or fins? If it cant get a good reading, is bad or has a bad wiring connection, the compressor won't be properly controlled.
To dive into this type of problem you need a FSM and EWD for your year truck. Here is the thermistor test chart for a '96, don't know if it's the same?
- Thread starter
- #54
Run a wire fron the connector to the pos side of 12v. I was just curious that if this indeed did not work, then that would rule out the sensor theory
. I am going to go test this now and will be back in a few. I do not believe we have tried this.
- Thread starter
- #55
I unplugged the compressor clutch and tried this, but could not get power to the clutch (i feel silly because i ran a wire from the connector to the battery and nothing, with a/c at max). So I plugged it back up and started it. I decided to see if it would run, and it is running right now and has not quit thus far (7 minutes). The coldest it has been is 71 degrees. However, the lo side is now reading 24 and the high side is reading less than 200????? Where did that come from?
- Thread starter
- #56
THIS IS REAL TIME:
The temp at the vent has dropped to 62 degrees and the clutch still engaged. Now the Lo side is reading 21-24 witha very slow veriation and the Hi side is steady at 185 .
The temp at the vent has dropped to 62 degrees and the clutch still engaged. Now the Lo side is reading 21-24 witha very slow veriation and the Hi side is steady at 185 .
- Thread starter
- #57
REAL TIME:
Here is exactly what is happening:
Temperature hits about 58 degrees.
Lo is 22
Hi is 185
The compressor stops at about 58 degrees (Lo shoots up on pressure, Hi stays the same)
When temp hits about 62 degrees, compressor starts and Lo goes to 22 and Hi to 185.
After about 1 minute, the air works its way back to 58 and the compressor stops and starts again when 61-62 degrees is reached.
I am going to try and jump the clutch directly to the battery again and see if it will get cooler.
Here is exactly what is happening:
Temperature hits about 58 degrees.
Lo is 22
Hi is 185
The compressor stops at about 58 degrees (Lo shoots up on pressure, Hi stays the same)
When temp hits about 62 degrees, compressor starts and Lo goes to 22 and Hi to 185.
After about 1 minute, the air works its way back to 58 and the compressor stops and starts again when 61-62 degrees is reached.
I am going to try and jump the clutch directly to the battery again and see if it will get cooler.
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You couldn't get power to the clutch? As soon as 12v is plugged in to the clutch lead it will snap closed and stay that way until unplugged?
Those pressures sound low and vent temps high, low on R134A? How much did you charge it with?
Those pressures sound low and vent temps high, low on R134A? How much did you charge it with?
- Thread starter
- #59
I disconnected the switch and ran a wire from the clutch side directly to the positive side of the battery and nothing happened (maye the connection was bad?).
They said they charged it with 28.somthing-or-another +-1.76oz. The guages were reading Lo 30 and Hi 225 early yesterday. I thought maybe they didn't charge it enough, but by what my guages say it could use a little more. The cycle between 58 and 61 is weird though.
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Gieser said:
At the clutch, where you unplug it to remove the compressor, then put power to the wire going to the clutch.
Gieser said:
28 oz sounds about right, it's cooler out in the evening causing lower pressure readings.
