What year?
ABC's of 80's Cooling Part III - Press Switch (1 Viewer)
- Thread starter SUMOTOY
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What year?
Odd that yours is working that way. We have similar temperatures here in Texas 100+°F days. My Aux fan is triggered by the medium switch as well. On a hot day my fan will come on within 10-15 seconds of start up...so that part of yours sounds right. But your 'run on' is certainly an issue. I've never had mine 'run on' for over a couple of minutes after shut down. Usually less than a minute.
As soon as you shut your AC off the high and low side pressures will begin to equalize (to static pressure). This can take several minutes to occur but at some point in that action....your system should reach a pressure of less than 156 psi (the point at which the switch should cut the fan off). In theory (with R134a) will have a static pressure of 156 psi at 114°F. So anything above this (depending upon how accurate your trinary switch is) would indeed cause extended run-on.
I'm wondering if your pressure switch is simply inaccurate?
The only other possibility would be a grossly overcharged system that is running at very high pressures to begin with and is taking a long time to equalize after shut down.
You could confirm that possibility (and record your static pressure) by using a set of manifold gauges.
My medium switch comes on immediately with the AC in the morning when the car has cooled off. As I write this, the medium pressure switch is still 'on' (though I switched the fan off). Agreed it sounds like I need to confirm correct system pressure. Thats what I'll plan on doing next.
The 91 is old enough to where it came with the older refrigerant gas type (can't recall the names right now), and the carfax made it look like it was switched over to the new gas by the dealer years ago. Perhaps the switch is tuned for a different gas? Or was not switched over properly? Other questions I'll be lookin into.
The 91 is old enough to where it came with the older refrigerant gas type (can't recall the names right now), and the carfax made it look like it was switched over to the new gas by the dealer years ago. Perhaps the switch is tuned for a different gas? Or was not switched over properly? Other questions I'll be lookin into.
I was going to ask you if you had R12 in there. No idea if that would change it enough for it to act the way it is though.
IF yours has been converted from R12 (which it had from the factory) to R134a, it will be readily apparent by the 'fittings'. The old R12 fitting were screw on fittings and R134a uses two different size Quick Connect fittings. There might also be a 'conversion' tag affixed over the factory tag on the radiator support (if the conversion was done properly).
Pressures between R12 and R134a are roughly the same for the low side (suction side and evaporator) but with R134a... is higher on the high side (condenser).
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FWIW I have a 97 and it turns off in 2-3 minutes after a 45 min drive in 100f ambient heat.
That agrees with what mine does. Run-on not more than 2 minutes (if that).
New OEM pressure switch is only $36. Any idea if you need to depressurize the system to change that?
EDIT: yeah looks like you do. I'll inquire about throwing a new one on when the mechanic re-does the refrigerant to the proper amount.
EDIT: yeah looks like you do. I'll inquire about throwing a new one on when the mechanic re-does the refrigerant to the proper amount.
Yes, you'll have to evacuate the system to replace. But since you will be doing that anyway (to recharge) then this would be the time to replace it. Make sure the tech knows to use the correct amount of R134a refrigerant and not to go by the amount specified on any old 'sticker' under the hood since it would be too much. Any decent A/C tech will know this.
Hopefully this will resolve your problem, but in the least...it will baseline your A/C (refrigerant charge anyway).
Wrote up and posted some pics of my build:
forum.ih8mud.com
Seeing better after run behavior on cooler days (only 104F), but still longer than what others are reporting (5-8 min after runs).
Confirming I have an R-12 system still, with unknown pressure readings that was mystery serviced by PO.
Builds - bcomnes' 1991 3FE FJ80 Build
All the original PNs for the various bolts and stuff are no longer made, and tracing down the bizarro JIS Toyota bolts elsewhere has proven quite difficult. Of course I could throw on regular metric bolts, but in case any one else wants to do this, here are the specs of replacement bolts that...
forum.ih8mud.com
Seeing better after run behavior on cooler days (only 104F), but still longer than what others are reporting (5-8 min after runs).
Confirming I have an R-12 system still, with unknown pressure readings that was mystery serviced by PO.
NorCalFJ100
SILVER Star
Bump to this fantastic thread! Thanks to Sumotoy (who appears to no longer be on mud) and all the other contributors! I am an electrical n00b. Just wondering if I can wire this as described many times BUT use my SwitchPros if I want to override the fan to turn it on at any given time.
Yes you can. Just share the pressure switch trigger wire to the relay.
dragging this back to the top b/c i've noticed something regarding the female pins for the a/c pressure switch
the consensus seems to be that 82998–12270 is the part number for the pins that need to be added to the pressure switch. the wire repair manual shows these to be 2.3 female pins with the weather sealing.
however, my read of the EWD shows the housing part to be 90980-10943, a female 4-pin waterproof type. this calls for 82998-12440, or 2.3II female pins. my understanding is the 2.3II pins are an improved design over the older 2.3, but i'm not sure if the pins are inter-changeable in the housings.
EWD connector drawing:
repair manual matching housing:
housing to repair wire table:
notice the 2.3II and -12440 part number
more details on 2.3 and 2.3II pins w/ associated part numbers:
one more thing i noticed is this chart has a note about 6mm pitch type low insertion force, but those pins have a different part number than all other references to the a/c pressure switch?
the consensus seems to be that 82998–12270 is the part number for the pins that need to be added to the pressure switch. the wire repair manual shows these to be 2.3 female pins with the weather sealing.
however, my read of the EWD shows the housing part to be 90980-10943, a female 4-pin waterproof type. this calls for 82998-12440, or 2.3II female pins. my understanding is the 2.3II pins are an improved design over the older 2.3, but i'm not sure if the pins are inter-changeable in the housings.
EWD connector drawing:
repair manual matching housing:
housing to repair wire table:
notice the 2.3II and -12440 part number
more details on 2.3 and 2.3II pins w/ associated part numbers:
one more thing i noticed is this chart has a note about 6mm pitch type low insertion force, but those pins have a different part number than all other references to the a/c pressure switch?
Malleus
Far west of Siegen
You're confusing the repair wires with the terminals; only the repair wires (as opposed to the terminals, with part numbers) are listed in the repair manual, as this was intended to be a shop resource. The repair wires are a terminal, sealing grommet and (approx) 4" long wire. The intention was the shop mechanics/technicians would cut a bad wire from the harness and, using a butt connector, splice in a replacement wire, to save time. Since your time is free (you don't charge yourself, right?), you should repair/modify the harness the way it was originally built, IMHO.
2.3 and 2.3II terminals are interchangeable in the housings; the 2.3II allow for larger diameter (gauge) wires to be used (the "D" dimension). Check with Ballenger for terminals, seals (grommets) and housings. They also have sets of complete parts that you can use to make up the connection(s) you need. Search for Sumitomo parts for sealed housings; Sumitomo and Yazaki are both used for the non-sealed housings and terminals.
2.3 and 2.3II terminals are interchangeable in the housings; the 2.3II allow for larger diameter (gauge) wires to be used (the "D" dimension). Check with Ballenger for terminals, seals (grommets) and housings. They also have sets of complete parts that you can use to make up the connection(s) you need. Search for Sumitomo parts for sealed housings; Sumitomo and Yazaki are both used for the non-sealed housings and terminals.
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thanks for the info, sounds like you've been down this road before
i do plan on sourcing uncrimped terminals vs using the repair wires (i'm also planning out a keyless/remote start T-harness to mimic the port installed TVSS, so i'll need many of the 2.3II unsealed terminals) but wanted to make sure i buy the right yazaki female terminals for pressure switch, and saw this discrepancy where the repair manual specs wires w/ the 2.3II terminals but the forum threads call for wires w/ the 2.3 end. 99.9% certain i've read the manual right. but if 2.3 and 2.3II terminals will both insert into the 90980-10943 housing, then that explains it....it doesn't really matter
can you double check my part numbers for terminals and seals? while balenger carries the terminal, they don't list the seal? they also only have the 16-18 ga terminal, not the -4027 terminal for thicker wire.
7116-4026 are the 2.3II sealed female terminals for 16-18 gauge wire
7158-3007-10 are the grey seals for 16-18 gauge wire
Malleus
Far west of Siegen
The end of the terminals which connect to each other are only areas the housings care about; the rest sticks out the rear end. AFAIK, 2.3 and 2.3II are functionally identical, with respect to the terminal interface. I believe they will both fit into the same housings. Ask Ballenger for a sample if you want to make certain. Call them, they are really good people and have always been very helpful when I asked questions or advice.
Ballenger has black, brown and green seals, for example:
Search for seals, if you don't find them, call. I can't help you with their part numbers, becasue I've only bought what I needed to fix the problems I had. Sorry.
Be very careful about wire gauges and outer diameters. The US/JIS automotive standards are not equivalent (and to make matters worse, you have to do math to equate them because we size wire by the die that makes it, they size wire by the cross-sectional area, which is how the EEs calculate the size required), and Toyota specified different insulation thicknesses by specifying different wire types. That's why there are different seal sizes for the same conductor sizes.
You need to measure the wire insulation OD, then pick the seal for that. The terminals are easier; 2.3II will accept a wider range of conductor sizes than the other terminal types, for the same housings.
Ballenger has black, brown and green seals, for example:
Search for seals, if you don't find them, call. I can't help you with their part numbers, becasue I've only bought what I needed to fix the problems I had. Sorry.
Be very careful about wire gauges and outer diameters. The US/JIS automotive standards are not equivalent (and to make matters worse, you have to do math to equate them because we size wire by the die that makes it, they size wire by the cross-sectional area, which is how the EEs calculate the size required), and Toyota specified different insulation thicknesses by specifying different wire types. That's why there are different seal sizes for the same conductor sizes.
You need to measure the wire insulation OD, then pick the seal for that. The terminals are easier; 2.3II will accept a wider range of conductor sizes than the other terminal types, for the same housings.
for real. this.
i had my micrometer out last night to measure all the spare wire i've acquired over the years. hardly any of it is marked at all so i don't know if its 18, 16, 10, etc other than by making an educated guess. i had the micrometer in MM so i could compare it to the yazaki specs, and now i'm more frustrated and confused than before i started. no wonder toyota sells butt connectors and 160mm repair wires.
so now i'm in the market for all new wire in various colors and sizes; 18-10 awg
and a good set of crimpers for yazaki and deutsch terminals, and 4 awg lugs
Malleus
Far west of Siegen
Ballenger sells the crimpers. I have a set and really like them:
The wire, at least in the engine bay and other exterior areas, AFAIK, is not Yazaki, but Sumitomo, most of it AEX type. The dash harness is also Sumitomo, but it has several types of wires in it, some shielded, some not, whereas the engine and transmission harnesses, again AFAIK, are all the same AEX (or equiv) type.
I have been searching for some time, but have been unable to find a domestic source for Sumitomo wire.
You can buy it from Japan, but not in the quantities that would make sense for even a complete harness rebuild on a whole truck. Several Chinese wire companies offer JIS/Automotive grades, equivalent to what was used, but I'm not inclined to do business with any of them. The domestic rebuilders I've spoken to don't seem to have the same regard for wiring they do for body work. They are all happy to harvest old wiring from old harnesses, for their "new" builds.
The wire, at least in the engine bay and other exterior areas, AFAIK, is not Yazaki, but Sumitomo, most of it AEX type. The dash harness is also Sumitomo, but it has several types of wires in it, some shielded, some not, whereas the engine and transmission harnesses, again AFAIK, are all the same AEX (or equiv) type.
I have been searching for some time, but have been unable to find a domestic source for Sumitomo wire.
You can buy it from Japan, but not in the quantities that would make sense for even a complete harness rebuild on a whole truck. Several Chinese wire companies offer JIS/Automotive grades, equivalent to what was used, but I'm not inclined to do business with any of them. The domestic rebuilders I've spoken to don't seem to have the same regard for wiring they do for body work. They are all happy to harvest old wiring from old harnesses, for their "new" builds.
