Hi Folks - I need some AC troubleshooting help. I have searched extensively in the forums, but can't find an answer (at least one that clicks for me), so am hoping that with the info below someone will recognize that I have an obvious problem, or if not, point me in the right direction for further troubleshooting. I am definitely learning the AC stuff as I go, so please feel free to call out any mistakes I made below.
Tools purchased/used, and threads referenced are listed at the end of this post.
So, here goes...
What I Started With
When purchased, the AC was not blowing cold (dash switch light would come on, and compressor was engaging). Local shop added R12. It blew cold for ~4 months until one day while highway driving I started smelling something burning, and noticed the air temperature at the vent decreasing rapidly. I switched off the AC with the dash switch, and pulled over. Upon inspection the compressor had blown oil out of it (all over the engine compartment). I continued my drive with the AC off, until I started hearing a noise from the engine. Upon further inspection the compressor was very difficult to turn (clutch not engaged), so I removed the AC belt in a gas station parking lot and continued my trip (LA to MT and back). It stayed this way until a few weeks ago when I decided to dive in to fix it.
What I Have Done So Far
-Replaced the compressor with a new unit from Coolstream (Denso 471-1433)
-Replaced the receiver/drier with a new unit from Coolstream (Denso 478-0101)
-Added 0.7 oz of mineral oil to the receiver drier, per FMS (also from Coolstreeam #MT3048)
-Removed and cleaned evaporator (should have tested the pressure switch and thermistor, but didn't)
-Pulled vacuum and charged with two 12oz cans of R12 that I bought out of the trunk of a sketchy guy from Craigslist (assuming I am now below spec of 28oz in system)
Current State
-AC Compressor does not engage
-When jumped, AC blows at 44℉ (blower: high, RPM at 2k) and can see bubbles in the sight glass
-Need some help with troubleshooting (below)
Charging
-After installing the compressor and receiver drier, I followed the instructions in post #14 of This Thread along with this youtube video to pull a vacuum, and charge (I'm sure the video content is obvious to some, but being an AC noob it was helpful to me).
-I did everything in the instructions, and couldn't get the compressor engage (pressure was building on the gauges, R12 can tapped, nothing happening)
-I jumped the compressor, and added the two cans of R12. Temp at vent steadily decreased until about 55℉
-Shut everything down, removed compressor jumper.
-Restarted engine, turned fan on, switched AC on. Compressor would not engage.
Troubleshooting: I then began working my way through the troubleshooting section of the FSM, beginning with the "Magnetic clutch does not engage" section on page AC-8
(a) FL (30A CDS) blown - Nothing else on the truck is non-operational. Am I missing something?
(b) Magnetic clutch relay faulty - Does this refer to the Heater Relay?
(c) Magnetic clutch faulty - Checked/Good
(d) A/C Fuse faulty - Checked/Good
(e) A/C Switch faulty - Checked/Good
(f) Thermistor faulty - Am I correct that I can't check without recovering refrigerant and pulling evaporator?
(g) A/C Amplifier faulty -
Testing conditions: IGN on, temp control lever Max Cool, Blower switch Hi
Continuity
6-Ground: FAIL
7-6: Good
8-9: Good
9-Ground: FAIL
Voltage
2-6: Good
3-6: Good
A-6: FAIL
Based on this my guesses are that I have a bad ground on the WB (white w/ black) ground wire OR the thermistor is bad. Thoughts?
Amplifier passes a visual check (no burned out pins)
(h) Pressure switch faulty -
I am not totally clear on how/where to test this, but here is what I tried.
-Based on the wiring diagram on page AC-4, I tested continuity between the Y (yellow) and YG (yellow w/ green) wires at the amplifier harness plug (pins 2 and 3 in the pic above). Here is a video of the results. Readings went from 0 to ~12.6 in a few seconds.
Also, here are the pressures at the gauges with the following testing conditions: Compressor jumped, Blower at high, Temp control at cool, AC switch on.
Low: 18psi (spec is 21-28psi)
High: 235psi (spec is 206-213)
Based on this I am not sure if my pressure switch is bad, or if I am low on refrigerant (causing the non-spec reading).
(i) Wiring or ground faulty - Possible. See above "amplifier faulty" section
(j) Refrigerant empty - Not empty, but not full either
Tools Used/Purchased
-Gauges (borrowed)
-Vacuum pump - Amazon $58.99
-Higher Quality Oil for Vacuum Pump (per Amazon comments) - Amazon $16
-R12 Can Tap - Amazon $8.49
-High side R12 Adaptor #MT0961 - Coolstream $14.19 (also available from Autozone for $9.79) *this is needed to connect gauges to the high side compressor port. Found in this thread (thanks @1972FJ55)
For others, these were threads that I found helpful:
-Yet another AC Thread by @georgebj60 - Great pictures
-Heater and AC System Re-Foam by @red66toy - Excellent writeup for removing, cleaning, and re-foaming evaporator case
-FJ62 New AC Compressor Part Number & R134 Fittings by @PNWFJ80 - If retrofitting to r134, this is the list
-Stay with R12 or convert to R134a - Great summary of pros/cons
-FJ62 A/C overhaul with Denso 10P15C compressor rebuild by @Spook50
Thanks everyone,
Dave
Tools purchased/used, and threads referenced are listed at the end of this post.
So, here goes...
What I Started With
When purchased, the AC was not blowing cold (dash switch light would come on, and compressor was engaging). Local shop added R12. It blew cold for ~4 months until one day while highway driving I started smelling something burning, and noticed the air temperature at the vent decreasing rapidly. I switched off the AC with the dash switch, and pulled over. Upon inspection the compressor had blown oil out of it (all over the engine compartment). I continued my drive with the AC off, until I started hearing a noise from the engine. Upon further inspection the compressor was very difficult to turn (clutch not engaged), so I removed the AC belt in a gas station parking lot and continued my trip (LA to MT and back). It stayed this way until a few weeks ago when I decided to dive in to fix it.
What I Have Done So Far
-Replaced the compressor with a new unit from Coolstream (Denso 471-1433)
-Replaced the receiver/drier with a new unit from Coolstream (Denso 478-0101)
-Added 0.7 oz of mineral oil to the receiver drier, per FMS (also from Coolstreeam #MT3048)
-Removed and cleaned evaporator (should have tested the pressure switch and thermistor, but didn't)
-Pulled vacuum and charged with two 12oz cans of R12 that I bought out of the trunk of a sketchy guy from Craigslist (assuming I am now below spec of 28oz in system)
Current State
-AC Compressor does not engage
-When jumped, AC blows at 44℉ (blower: high, RPM at 2k) and can see bubbles in the sight glass
-Need some help with troubleshooting (below)
Charging
-After installing the compressor and receiver drier, I followed the instructions in post #14 of This Thread along with this youtube video to pull a vacuum, and charge (I'm sure the video content is obvious to some, but being an AC noob it was helpful to me).
-I did everything in the instructions, and couldn't get the compressor engage (pressure was building on the gauges, R12 can tapped, nothing happening)
-I jumped the compressor, and added the two cans of R12. Temp at vent steadily decreased until about 55℉
-Shut everything down, removed compressor jumper.
-Restarted engine, turned fan on, switched AC on. Compressor would not engage.
Troubleshooting: I then began working my way through the troubleshooting section of the FSM, beginning with the "Magnetic clutch does not engage" section on page AC-8
(a) FL (30A CDS) blown - Nothing else on the truck is non-operational. Am I missing something?
(b) Magnetic clutch relay faulty - Does this refer to the Heater Relay?
(c) Magnetic clutch faulty - Checked/Good
(d) A/C Fuse faulty - Checked/Good
(e) A/C Switch faulty - Checked/Good
(f) Thermistor faulty - Am I correct that I can't check without recovering refrigerant and pulling evaporator?
(g) A/C Amplifier faulty -
Testing conditions: IGN on, temp control lever Max Cool, Blower switch Hi
Continuity
6-Ground: FAIL
7-6: Good
8-9: Good
9-Ground: FAIL
Voltage
2-6: Good
3-6: Good
A-6: FAIL
Based on this my guesses are that I have a bad ground on the WB (white w/ black) ground wire OR the thermistor is bad. Thoughts?
Amplifier passes a visual check (no burned out pins)
(h) Pressure switch faulty -
I am not totally clear on how/where to test this, but here is what I tried.
-Based on the wiring diagram on page AC-4, I tested continuity between the Y (yellow) and YG (yellow w/ green) wires at the amplifier harness plug (pins 2 and 3 in the pic above). Here is a video of the results. Readings went from 0 to ~12.6 in a few seconds.
Also, here are the pressures at the gauges with the following testing conditions: Compressor jumped, Blower at high, Temp control at cool, AC switch on.
Low: 18psi (spec is 21-28psi)
High: 235psi (spec is 206-213)
Based on this I am not sure if my pressure switch is bad, or if I am low on refrigerant (causing the non-spec reading).
(i) Wiring or ground faulty - Possible. See above "amplifier faulty" section
(j) Refrigerant empty - Not empty, but not full either
Tools Used/Purchased
-Gauges (borrowed)
-Vacuum pump - Amazon $58.99
-Higher Quality Oil for Vacuum Pump (per Amazon comments) - Amazon $16
-R12 Can Tap - Amazon $8.49
-High side R12 Adaptor #MT0961 - Coolstream $14.19 (also available from Autozone for $9.79) *this is needed to connect gauges to the high side compressor port. Found in this thread (thanks @1972FJ55)
For others, these were threads that I found helpful:
-Yet another AC Thread by @georgebj60 - Great pictures
-Heater and AC System Re-Foam by @red66toy - Excellent writeup for removing, cleaning, and re-foaming evaporator case
-FJ62 New AC Compressor Part Number & R134 Fittings by @PNWFJ80 - If retrofitting to r134, this is the list
-Stay with R12 or convert to R134a - Great summary of pros/cons
-FJ62 A/C overhaul with Denso 10P15C compressor rebuild by @Spook50
Thanks everyone,
Dave
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