ABC's of 80's Cooling Part III - Press Switch (1 Viewer)
- Thread starter SUMOTOY
- Start date
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Thanks Mot,
Yes, I did know where the switch was located. I was just wondering if Scott had documented the procedure of adding the pigtails with pics.
I am kind of a visual person.
Thank you though for the schematic, I appreciate it.
Flint
Yes, I did know where the switch was located. I was just wondering if Scott had documented the procedure of adding the pigtails with pics.
I am kind of a visual person.
Thank you though for the schematic, I appreciate it.
Flint
Flint:
I too thought I would need pics. However, everything became extremely clear once I got into it. If you follow the instructions to the letter of post #1, you can't go wrong. Just take your time.
Steve
94' 190,000
I too thought I would need pics. However, everything became extremely clear once I got into it. If you follow the instructions to the letter of post #1, you can't go wrong. Just take your time.
Steve
94' 190,000
i think sumo got tired of everyone bashing and critiquing every word he typed, so he has not been on this site for a while FWIW
going to do this install on the pressure switch now with the proper connectors...will post pics.
One of the best mods I have done to my 80.
Ok, I'd love to say that I put it all together and wired it up and it worked, but I can't get the fan to come on. I know it's wired correctly and when I put 12v directly to the relay wire the fan fires right up, but with the Medium a/c pressure switch terminals it's not working. The ground is good because other items are grounded there and I tested it....
The new connectors I installed in the a/c pressure switch harness seem a bit looser than the factory ones for the High and Low side, but the prongs on the switch are definitely long enough to make contact.
Could it be the pressure just purely isn't getting high enough to turn it on? I'm in N.Va. and the temps are still in the 70's and the coolant temp is getting up in the 195 range (scanguage).... Out of ideas here and appreciate input.
The new connectors I installed in the a/c pressure switch harness seem a bit looser than the factory ones for the High and Low side, but the prongs on the switch are definitely long enough to make contact.
Could it be the pressure just purely isn't getting high enough to turn it on? I'm in N.Va. and the temps are still in the 70's and the coolant temp is getting up in the 195 range (scanguage).... Out of ideas here and appreciate input.
Cruiser804
SILVER Star
Dude I am in NoVa also. Yeah, you need to get the pressure up. Mine will start after running for few minutes with the AC on high. Just ran out and checked it. AC on high truck running about 4-5 minutes and it kicks on.
- Thread starter
- #49
Press switch not working? Diagnostics
Still around, just more lurking than posting. It's quite possible that the pressure switch is functioning correctly. If you don't get to 195psi, the switch won't turn on the relay. Just for clarification, you are using the pressure switch as <ground> for the relay correct?
If you followed this mod exactly as in post 1, once the AC high pressure line gets to 195, you will complete the relay circuit to ground. If you connect the relay directly to ground and you get fan, you have either:
Bad pressure switch
Low on Freon - (Most likely)
Bad compressor
Any of the above can be diagnosed with a set of A/C guages.
HTH
Scott J
Still around, just more lurking than posting. It's quite possible that the pressure switch is functioning correctly. If you don't get to 195psi, the switch won't turn on the relay. Just for clarification, you are using the pressure switch as <ground> for the relay correct?
If you followed this mod exactly as in post 1, once the AC high pressure line gets to 195, you will complete the relay circuit to ground. If you connect the relay directly to ground and you get fan, you have either:
Bad pressure switch
Low on Freon - (Most likely)
Bad compressor
Any of the above can be diagnosed with a set of A/C guages.
HTH
Scott J
SUMO, thanks for the reply! I think quite a few people have anticipated you chiming in on this at some point...
"Just for clarification, you are using the pressure switch as <ground> for the relay correct? "
well, I have the relay grounded to the chassis on the passenger side and then I have the pressure switch grounded on the driver's side, and the ignition wire from the relay to one side of the pressure switch. With this method I did not get any fan activation well after the coolant temp was up around 195, so I'm assuming a/c pressure would have kicked the fan at that point if the switch was good and my wiring was correct...
Are you saying I need to:
1) run the ground wire from the relay to the pressure switch ground point on the chassis, or;
2) run the ground side of the pressure switch to the relay ground wire exclusively, or;
3) do something totally different?
Man, i need a diagram, I'm confusing myself here!
Thanks again for clarifying...really, I appreciate it...
"Just for clarification, you are using the pressure switch as <ground> for the relay correct? "
well, I have the relay grounded to the chassis on the passenger side and then I have the pressure switch grounded on the driver's side, and the ignition wire from the relay to one side of the pressure switch. With this method I did not get any fan activation well after the coolant temp was up around 195, so I'm assuming a/c pressure would have kicked the fan at that point if the switch was good and my wiring was correct...
Are you saying I need to:
1) run the ground wire from the relay to the pressure switch ground point on the chassis, or;
2) run the ground side of the pressure switch to the relay ground wire exclusively, or;
3) do something totally different?
Man, i need a diagram, I'm confusing myself here!
Thanks again for clarifying...really, I appreciate it...
- Thread starter
- #51
Wiring Instructions
That pressure switch is a <ground> switch! Let's go thru this carefully, from what you describe you are grounding your ignition feed when the pressure switch is on! From what I read, you have chosen to make this an ignition only mod (no after-run), so your wiring should be exactly as follows
RELAY = 4pin 30 or 40amp
Pin 30 = FROM 12v+ battery
Pin 87 = TO Aux Fan 12v+ input
Pin 86 = FROM 12v+ ignition (no afterrun) OR 12V+ batt (afterrun)
Pin 85 = To Med Pressure switch pin
MED PRESS SWITCH = gate switch = no pin orientation required
1 Med Pressure switch pin = From Fan Relay Pin 85
1 Med Pressure switch pin = To Chassis Ground
FAN
Red lead = From Relay Pin 87
Black/Brown lead = To Chassis Ground
The Medium Pressure Switch should be a ground gate for the Relay Activation. The Medium Pressure Switch should not be, nor was it designed to be a 12v+ load switch.
BTW, I spoke at length with a Automotive HVAC engineer regarding the indefinite after-run concerns posted in this thread. He thought it theoretically impossible ambient temps could be high enough to cause the pressure switch to read 195 indefinitely. As he explained it, on shutdown the system will equalize pressure thru the expansion tube until the freon reaches equilibrium pressure on both sides of the compressor - at much lower than the 195 of the switch.
HTH
Scott J
That pressure switch is a <ground> switch! Let's go thru this carefully, from what you describe you are grounding your ignition feed when the pressure switch is on! From what I read, you have chosen to make this an ignition only mod (no after-run), so your wiring should be exactly as follows
RELAY = 4pin 30 or 40amp
Pin 30 = FROM 12v+ battery
Pin 87 = TO Aux Fan 12v+ input
Pin 86 = FROM 12v+ ignition (no afterrun) OR 12V+ batt (afterrun)
Pin 85 = To Med Pressure switch pin
MED PRESS SWITCH = gate switch = no pin orientation required
1 Med Pressure switch pin = From Fan Relay Pin 85
1 Med Pressure switch pin = To Chassis Ground
FAN
Red lead = From Relay Pin 87
Black/Brown lead = To Chassis Ground
The Medium Pressure Switch should be a ground gate for the Relay Activation. The Medium Pressure Switch should not be, nor was it designed to be a 12v+ load switch.
BTW, I spoke at length with a Automotive HVAC engineer regarding the indefinite after-run concerns posted in this thread. He thought it theoretically impossible ambient temps could be high enough to cause the pressure switch to read 195 indefinitely. As he explained it, on shutdown the system will equalize pressure thru the expansion tube until the freon reaches equilibrium pressure on both sides of the compressor - at much lower than the 195 of the switch.
HTH
Scott J
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This is your problem and what SUMOTOY is trying to explain. the ground from the relay should go through the pressure switch and then to the ground.
Ah, so it looks like I have to remove the additional ground I have from the relay on the passenger side from the relay and only use the ground from the pressure switch.... I think it's starting to make sense.
I'll give that a shot. And again, thanks SUMO for the in depth replies...
I'll give that a shot. And again, thanks SUMO for the in depth replies...
Ok, here is how my fan is wired up. It's the Painless 30101 relay kit. Please let me know if I need to change something...(at work, can't confirm which pin is wired to what)
The "Black Wire" is to ground right behind the relay and the "Gray/White Wire" runs to one side of the a/c pressure switch and the other side of the pressure switch is to ground.
Thanks again...
http://www.painlessperformance.com/Manuals/30101Instruction.pdf
The "Black Wire" is to ground right behind the relay and the "Gray/White Wire" runs to one side of the a/c pressure switch and the other side of the pressure switch is to ground.
Thanks again...
http://www.painlessperformance.com/Manuals/30101Instruction.pdf
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From what I have followed on this thread, it looks like the black wire should go through the A/C switch, then to ground. The gray/white wire should go to an ignition source (if you only want the fan to run when the key is on)
Well, finally got it to work!!!!.....
I'd like to thank all of those that helped me get to this point...the academy...my parents....oh wait...
Thanks again guys, works like a charm. Amazing how well things work when you do it right!
I'd like to thank all of those that helped me get to this point...the academy...my parents....oh wait...
Thanks again guys, works like a charm. Amazing how well things work when you do it right!
Bump for a sweet mod. Thanks SUMO!
Yup, mine works awesome!
This mod helps make a/c in Phoenix work a little better especially in slow traffic and on the trails.
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