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Hello all, new here and new to Toyota's having just purchased my first one, a 1995 4Runner. When I bought it I knew the A/C was intermittent but thought it just needed to be serviced but this did not fix it. A/C will blow cold at night or in the mornings when the ambient temps are around 80f, but once it gets around 85f or higher the clutch is not getting the signal to engage. The oddity here is that when the compressor does kick on the engine temperature gauge slams over to cold and sticks there, disengage the A/C clutch and it returns to normal. Something elseI noticed is frequently when the clutch is engaged I can hear a light ratcheting noise from behind the glove-box, I assume it is a switch making the racket. Any ideas? Thanks in advance
slight ratcheting noise sounds like the flap to switch from heater core to ac evaporator is sticking as far as the ac not working when temps above 85 my first thought assuming Freon is full, is clogged condenser(no airflow) which will cause pressure to over build and system will shut off compressor also could be a bad ambient temp sensor or evap sensor but I'm not sure your truck has an A.T.S but the evap sensor will shut off compressure
also i can not think of any connection between compressor and engine temp sending unit sounds like more then one issue
Thanks for the reply Hippystyle. Not sure what "A.T.S" is? For the odd engine temp gauge issue I'm wondering if someone has monkeyed around with the wiring, just seems a really odd connection. I'm probably dropping this thing off at a local shop, between working OT and the gym I don't have the time to troubleshoot like I need to but thanks for the tips, maybe I can point the shop in the right direction and save some time.
On my 89 V6 4Runner there is a separate sensor for the temp gauge apart from the one that sends it's input to the ECM. If yours is like that then I can't think of a connection between the two. If your gauge reads off the same sensor as the ECM then factor the engine fan into the equation some how. Both the coolant temp sensor and the ac system will likely stroke up the fan. See if you see all three things at the same time. (Not confirmed information here.) Just giving you something to possibly think about.
As far as the clutch kicking out at higher temps, I absolutely agree with hippystyle on a condenser issue. Confirm with ac gauges.
slight ratcheting noise sounds like the flap to switch from heater core to ac evaporator is sticking as far as the ac not working when temps above 85 my first thought assuming Freon is full, is clogged condenser(no airflow) which will cause pressure to over build and system will shut off compressor also could be a bad ambient temp sensor or evap sensor but I'm not sure your truck has an A.T.S but the evap sensor will shut off compressure
also i can not think of any connection between compressor and engine temp sending unit sounds like more then one issue
If your A/C system is the original, a worn compressor will cause this as well. On mine, if the car is idle the AC will stop blowing cold air, when I start moving it will get cold again. low freon as well will cause this to struggle as well.
Thanks for all the answers guys. Stopped in to check on it and the mechanic says that inside the shop, anytime you start it cold the AC works fine for 10 to 15 minutes, then the clutch starts cycling and then quits. Once it cools off, regardless of outside temp, it will blow cold again but repeats the cycle. When I had it outdoors and it was hot it wouldn't blow cold ever. He was able to kick the clutch on at will by applying 6v to a pink colored wire in the bundle he thinks is to the relay but the relay itself is fine. He really needs a color coded wiring schematic to troubleshoot this thing so if anyone has one or knows where I might find one I'd appreciate it.
I read through several posts here on A/C problems before submitting this one, and they mention the components behind the glove box (pressure switch, relay, expansion valve, etc.) but neither of us see an easy way to access them behind that grey plastic shroud. How do you access these?
Generally the ambient air temp sensor shuts down the ac compressor when it senses low outside temperatures due to the fact that extremely low temperatures can cause poor oil circulation and starve the compressor. Inspect that sensor just for fun. I would remove it and try and jump power around it. It won't hurt a thing providing you are not in Antarctica at this time of year. It sure wouldn't hurt to go ahead and rule that one component out. I'm not sure where yours is but they are normally on the very front of vehicles near the grille where it can read more accurately the outside air temp.
Generally the ambient air temp sensor shuts down the ac compressor when it senses low outside temperatures due to the fact that extremely low temperatures can cause poor oil circulation and starve the compressor. Inspect that sensor just for fun. I would remove it and try and jump power around it. It won't hurt a thing providing you are not in Antarctica at this time of year. It sure wouldn't hurt to go ahead and rule that one component out. I'm not sure where yours is but they are normally on the very front of vehicles near the grille where it can read more accurately the outside air temp.
Thank you for responding but I'm not sure that really fits my 4Runner's symptoms; It blows cold without shutting down at night when temps are around 80f but won't kick on at all when it gets warmer. The mechanic suspects a component is warming up and failing because it will start when cold (as in the 4Runner has cooled off) but after 10 or 15 minutes the clutch disengages like clockwork.
I don't know much about the '95, but I'm certain the '93 and '94 don't have an ambient air sensor. http://web.archive.org/web/201102052.../2aircondi.pdf Those are R12 systems, so it is possible the wiring was changed post-R134a, but I doubt it.
The pressure switch and expansion valve are inside the cooling unit (which contains the evaporator). It's not a "gray plastic shroud," but a black plastic BOX.
The AC Amplifier is on top of the cooling unit, and as the schematic in the link above shows, that controls everything. The only relay you are likely to have (on the outside, lower part, of the cooling unit) is the AC cut-off relay. You don't mention if you have an automatic transmission, but 3VZE/4wd/Auto have an additional temp sensor in the water bypass (the chunk at the back of the block with all the sensors). That sensor activates the cut-off relay when the coolant is "too hot," cutting off (duh!) the AC. This sounds a little like your circumstance; you could try disconnecting the sensor to see if it changes things. (Or monitor the cutoff relay.)
[QUOTE=scope103;52330236]I don't know much about the '95, but I'm certain the '93 and '94 don't have an ambient air sensor. http://web.archive.org/web/201102052.../2aircondi.pdf Those are R12 systems, so it is possible the wiring was changed post-R134a, but I doubt it.
The pressure switch and expansion valve are inside the cooling unit (which contains the evaporator). It's not a "gray plastic shroud," but a black plastic BOX.
The AC Amplifier is on top of the cooling unit, and as the schematic in the link above shows, that controls everything. The only relay you are likely to have (on the outside, lower part, of the cooling unit) is the AC cut-off relay. You don't mention if you have an automatic transmission, but 3VZE/4wd/Auto have an additional temp sensor in the water bypass (the chunk at the back of the block with all the sensors). That sensor activates the cut-off relay when the coolant is "too hot," cutting off (duh!) the AC. This sounds a little like your circumstance; you could try disconnecting the sensor to see if it changes things. (Or monitor the cutoff relay.)
QUOTE]
Thanks Scope, it is an automatic tranny. I'll take this to the mechanic and give it a shot on Monday.
Thank you for responding but I'm not sure that really fits my 4Runner's symptoms; It blows cold without shutting down at night when temps are around 80f but won't kick on at all when it gets warmer. The mechanic suspects a component is warming up and failing because it will start when cold (as in the 4Runner has cooled off) but after 10 or 15 minutes the clutch disengages like clockwork.
What your mechanic is saying is what I'm thinking as well. It's probably one of your switches. There are several of them that will cut out your compressor including the high side pressure switch, the low side pressure switch, the ATS (If Equipped) and apparently the coolant temp sensor. It could be wiring as well but I'd test the circuit at each switch while it's giving you the trouble. The reason I suggested the ATS as something to test is because it (if equipped) uses temperature readings to close or open the circuit and there wouldn't be any real consequence to removing it from the circuit. You could jump around any of the switches so long as you had an eye on a set of gauges to verify that your pressures aren't getting out of range. I guess you could disconnect the wire from the compressor and hook it to a test light while you did your wire wiggling and sensor testing. That way you would just see a light when the signal is being sent to run the compressor. I'm actually working on an ac right now and that is the first time I've thought of that. I'm going to rig up a light right now.
I think Scope is on the right track. The temp gauge falling out when the compressor is on can't be a coincidence and those two sensors are awful close together.
bottom line is you need gages man, all of us are just guessing seams every response I read makes me think "if only we knew the pressures"
also make sure its over 85 degrees when you take it in
bottom line is you need gages man, all of us are just guessing seams every response I read makes me think "if only we knew the pressures"
also make sure its over 85 degrees when you take it in
I dropped the Runner off last week, still not fixed, has him scratching his head.. The Freon is properly serviced, he has checked that with gauges, and I live in Oklahoma so 85f would be cool at this point lol. I provided the ideas all you guys suggested but I think I'm just annoying him at this point. What he really needs is a wiring schematic of the AC system in color but neither of us can locate one, all we can locate are black and white. If he gets it figured out or gives up I will be sure to update this post though, thanks fellas.
UPDATE: Looks like we have a bead on the A/C problems, three to be exact.....so far. The coolant temp sensor plug/wire was corroded and loose, the wire pulled right out so there was an intermittent cut off signal there and I suspect this is when the engine temp gauge would peg to the left, the temp sensor itself is bad, and the relay on the evaporator coil is also bad - that is the part that is failing when it gets hot. The mechanic grounded the temp sensor and the A/C will run until the relay gets hot and cuts off, he put a source of cool air on it and it ran fine for an hour before cutting out again. Now my problem is locating a replacement relay, the temp sensor I have located but neither the me, the mechanic, or local Toyota dealership can find this relay
anywhere. I know I have read on this forum of people replacing it so if someone could turn me on to a source I'd sure appreciate it.
I know you'd rather match the existing connector (I would), but electrically it's just a garden-variety 12v SPST relay. You could replace both the relay and it's socket for not much money at all. https://www.amazon.com/Auto-Truck-Re...QH6/ref=sr_1_8
But before you get tooo excited, remember that there are (at least) THREE temp sensors in the water bypass: ECT, Temp Gauge, and A/C Cutoff. They don't help each other out, so a broken connector on ONE sensor will not both mess up the gauge AND the air conditioning. (Of course, they are CLOSE to each other, so if one connector is corroded out I'd suspect them all.)
I know you'd rather match the existing connector (I would), but electrically it's just a garden-variety 12v SPST relay. You could replace both the relay and it's socket for not much money at all. https://www.amazon.com/Auto-Truck-Re...QH6/ref=sr_1_8
But before you get tooo excited, remember that there are (at least) THREE temp sensors in the water bypass: ECT, Temp Gauge, and A/C Cutoff. They don't help each other out, so a broken connector on ONE sensor will not both mess up the gauge AND the air conditioning. (Of course, they are CLOSE to each other, so if one connector is corroded out I'd suspect them all.)
Thanks Scope, if I can't find a direct replacement I'll ask him to do what you suggest and just replace with a compatible relay/plug.
UPDATE: AC is fixed! Did not replace the temp sensor, just grounded the wire to the intake. The clutch relay I couldn't find anywhere on-line or at Toyota Surplus Parts was found on the shelf at a local O'Rielly's. A/C now blows cold without cutting out and the temp gauge functions as it should at all times. The best part is that even with all the time he spend on it D&D Automotive only charged me $267 including parts and Freon, I really thought the damage would be worse. Thanks for all the help guys.
Join Date: Dec 2013
Posts: 9In mi case after rebuilding the motor the A/C did not work at first an than out off the blue it stored to work, it did so for a wile about 2 moths or so, than it wood com on and off intermittently tell now the cloche on the compressor will not engage, works fine when i apply direct power to it and blows cold !! check the cut off relay it dos not check good when i did the test that the Toyota manual calls for so i bout another one, how ever its doing the same thing the cloche will not engage and the relay dos not pass the test, how ever when i punched the wire #3 of the relay to test for + the relay kicked in an so did the compressor it also works good when i jump the plug 1 to 3 and 2 to 4 off the cutoff relay.Any ideas???
08-02-2016, 04:04 PM
