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Car Forum / Honda Cars / February 2005Need to replace thermo switch and thermostat in 95 Civic
I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic LX. The radiator fan does not come on when the AC is switched on (though the compressor fan works okay). I checked the fan relay by putting 12VDC across the coil and I hear a click, plus I get continuity across the contacts. I've bent the pins in case the socket connection is bad. Shorting out the contacts in the fan relay socket causes the fan to come on, so the fan itself is okay. That's the disgnostic work I've done so far. Thanks to Tegger's FAQ, I've been able to locate the thermo switch, but I cannot figure out how to remove the connector for testing purposes. It's rotated in such a way that I can't see do undo the connector, and help here? Aside from the connector, are there any pitfalls I should know about when replace the thermo switch? It's fairly easy to get to, so I should be able to do it myself. Also would like to change the thermostat, but never having done that I need some assistance. First, in locating it. Then in determine what type it is (med temp/high temp) and removal procedure. I've read that on later model Honda's it's on the lower radiator hose but I can't see it. > I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic > LX. The radiator fan does not come on when the AC is switched on [quoted text clipped - 4 lines] > causes the fan to come on, so the fan itself is okay. That's the > disgnostic work I've done so far. Does the rad fan come on when the engine has been in heavy traffic for 5 minutes? Warm it up all the way, take it to a quiet side street somewhere, and then simulate heavy stop-and-go "inch forward" traffic for 5 minutes. If your fan is not coming on, the temp gauge will begin to rise. > Thanks to Tegger's FAQ, I've been able to locate the thermo switch, > but I cannot figure out how to remove the connector for testing [quoted text clipped - 10 lines] > on later model Honda's it's on the lower radiator hose but I can't see > it. The thermostat is at the TOP of the engine, where the heat goes. The lower hose is a long, snaky thing that goes from the bottom of the rad to the thermostat housing. Follow the hose from the rad to the other end and there it is. WORD OF WARNING: DO NOT INSTALL AN AFTERMARKET THERMOSTAT. Those things are much too likely to cause you no end of grief. An OEM (and gasket) is less than $20. There is only one rating of OEM: 90C/194F. DO NOT install a cooler one!  SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > The thermostat is at the TOP of the engine, where the heat goes. The lower > hose is a long, snaky thing that goes from the bottom of the rad to the [quoted text clipped - 6 lines] > > There is only one rating of OEM: 90C/194F. DO NOT install a cooler one! I'm confused. I was thinking that was the thermo switch/sensor, since it labeled such on the FAQ: http://www.tegger.com/hondafaq/overheating/overheating-index/index.htm (photo next to "Thermo Sensor Check") Are the thermo sensor/thermostat one and the same? Also, tnx for the tip on using an OEM part, I'll be sure to do that. > I'm confused. I was thinking that was the thermo switch/sensor, since > it labeled such on the FAQ: > http://www.tegger.com/hondafaq/overheating/overheating-index/index.htm > (photo next to "Thermo Sensor Check") > > Are the thermo sensor/thermostat one and the same? No. The thermostat is a big round mechanical thing about 2" in diameter. It's inserted into the coolant stream and is supposed to block coolant flow until a proper temperature is reached. The only way to change it is to drain the coolant and remove the thermostat housing. http://tegger.com/hondafaq/misc/thermostat.jpg All the other things are electronic and serve to turn fans on and such. They might tap into the coolant stream so they can sense the temperature, but you can usually change them without draining the coolant. SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > > The thermostat is at the TOP of the engine, where the heat goes. The lower > > hose is a long, snaky thing that goes from the bottom of the rad to the [quoted text clipped - 10 lines] > I'm confused. I was thinking that was the thermo switch/sensor, since it > labeled such on the FAQ: http://www.tegger.com/hondafaq/overheating/overheating-index/index.htm > (photo next to "Thermo Sensor Check") > > Are the thermo sensor/thermostat one and the same? > > Also, tnx for the tip on using an OEM part, I'll be sure to do that. DG, in your post refering to the photo in "Thermo Sensor Check" The brass colored Sensor is the Thermo Switch. The wires under the bolt to the right are ground wires. The bolt there holds the cover to the thermostat, the hose on the right side of the picture is the lower radiator hose. Remove this hose and another bolt(or two) and the cover for the thermostat comes off. > Does the rad fan come on when the engine has been in heavy traffic for 5 > minutes? > > Warm it up all the way, take it to a quiet side street somewhere, and then > simulate heavy stop-and-go "inch forward" traffic for 5 minutes. If your > fan is not coming on, the temp gauge will begin to rise. I forgot to answer this part -- no the rad fan does not come on, whether driving at speed for a while or stop-and-go. The temp guage doesn't rise to much, no more than 1/3 of the way up. >> Does the rad fan come on when the engine has been in heavy traffic >> for 5 minutes? [quoted text clipped - 6 lines] > whether driving at speed for a while or stop-and-go. The temp guage > doesn't rise to much, no more than 1/3 of the way up. Sounds like your thermostat may be going bad. You should be up to just below the half-way mark on the gauge in less than ten minutes of driving. How's your heater output? The rad fan will NOT come on until the coolant temperature is high enough to close the contacts in the fan switch. You may never be getting there. SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ Incorrect, my Acura Vigor price for the thermostat was 86$ sale price, 110$ regular price. Plus 11$ for gasket! 15$ at Canadian Tire... I still bought the OEM. Adrian >> I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic >> LX. The radiator fan does not come on when the AC is switched on [quoted text clipped - 38 lines] > > There is only one rating of OEM: 90C/194F. DO NOT install a cooler one! > Incorrect, > > my Acura Vigor price for the thermostat was 86$ sale price, 110$ > regular price. Plus 11$ for gasket! Whooooa! Mine was $12 at the dealer. I've NEVER bought an OEM thermostat for any make that was more than $20. Maybe I'm buying the wrong cars. > 15$ at Canadian Tire... I still bought the OEM. You won't regret it. SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > Incorrect, > > my Acura Vigor price for the thermostat was 86$ sale price, 110$ regular > price. Plus 11$ for gasket! damn. ida taken it out, got a part number off it then cross-referenced online. its almost gotta be shared with something else. then again, thats the wacky 5 cyl, huh? > I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic LX. The > radiator fan does not come on when the AC is switched on (though the [quoted text clipped - 16 lines] > (med temp/high temp) and removal procedure. I've read that on later model > Honda's it's on the lower radiator hose but I can't see it. The connector to the thermo switch has "lock" that must be raised about 1/16 of an inch before it can be unpluged. You may have to back the thermo switch a quarter turn or so to get to this "lock". The thermostat is a couple of inches to the right of the thermo switch an a bit higher. Be aware that there is still antifreeze in this part of the engine even after you drain the radiator. See Tegger's FAQ under radiator does not come on by REMCO for a lot of good data. Ernie > The connector to the thermo switch has "lock" that must be raised about > 1/16 of an inch before it can be unpluged. You may have to back the [quoted text clipped - 9 lines] > for a lot of good data. > Ernie Thanks, Ernie. I lifted the tab with a screwdriver and it popped right off. I ended up running a wire from the thermo switch connector to ground, so the radiator fan stays on when the car is running. I've already purchased the replacement thermo switch, but need to go back and get a wrench big enough to put it on. One other thing I noticed was that the radiator was under pressure even after 2-3 hours of sitting. Attempting to remove the rad cap cause coolant to squirt out. I would have though any pressure would have dissipated during that time. > > The connector to the thermo switch has "lock" that must be raised about > > 1/16 of an inch before it can be unpluged. You may have to back the [quoted text clipped - 21 lines] > to squirt out. I would have though any pressure would have dissipated during > that time. Yeah, 2 or 3 hours does seem to be a long time for the radiator to cool. When I was having trouble with mine It would cool in an hour or less. There could be a problem with the radiator cap or the line to the over flow tank. When the coolant gets hot it should expand and flow into the overflow tank and then be drawn back into the radiator as the engine cools. I see a lot of talk about having air in the hoses or the engine on this news group, but I don't know if that could be your problem. I think the rad cap should allow coolant to flow to the overflow tank at about 16 lbs pressure. Ernie > > The connector to the thermo switch has "lock" that must be raised about > > 1/16 of an inch before it can be unpluged. You may have to back the [quoted text clipped - 21 lines] > to squirt out. I would have though any pressure would have dissipated during > that time. Yeah, 2 or 3 hours does seem to be a long time for the radiator to cool. When I was having trouble with mine It would cool in an hour or less. There could be a problem with the radiator cap or the line to the over flow tank. When the coolant gets hot it should expand and flow into the overflow tank and then be drawn back into the radiator as the engine cools. I see a lot of talk about having air in the hoses or the engine on this news group, but I don't know if that could be your problem. I think the rad cap should allow coolant to flow to the overflow tank at about 16 lbs pressure. Ernie I just replaced the thermo switch, and the radiator fan *still* doesn't come on, even with the AC switched on (the AC compressor fan on driver's side does come on). I measured the new thermo switch by putting an ohmmeter across the terminals and lowering it into a pan of boiling water. After the switch closed I got 1 ohm of resistance. The old thermo switch read 8 ohms. So I guess it was bad? I'm not sure what else it could be.... shorted one side of the thermo switch connector to ground does make the fan come on while the engine is running. There's nothing else in the circuit as far as I know. The temp guage never rises above 1/3 level (so far). Tegger, you had asked about the heat output in the passanger compartment. At times, it seems to be normal. Other times, it seems to be cool, even when the temp setting is over at max. Could this be due to a bad thermostat or something else? > The temp guage never rises above 1/3 level (so far). Tegger, you had > asked about the heat output in the passanger compartment. At times, it > seems to be normal. Other times, it seems to be cool, even when the > temp setting is over at max. Could this be due to a bad thermostat or > something else? Personally, I think you're barking up the wrong tree here. 1 ohm or 8 ohms means nothing. If the temp gauge never gets past 1/3, the rad fan WILL NOT START NO MATTER WHAT. If you simulated the heavy stop-and-go traffic like I said for AT LEAST 5 MINUTES, and the temp gauge DID NOT RISE, then your engine IS NOT HEATING UP ENOUGH to make the fan come on. I do believe you have a bad thermostat. Replace with new **OEM** for $20, then report back, BEFORE you spend bigger bucks on the thermoswitch. SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > I just replaced the thermo switch, and the radiator fan *still* doesn't come > on, even with the AC switched on (the AC compressor fan on driver's side > does come on). I don't believe the rad fan is supposed to come on when you turn on the A/C. I have seen cars where the rad fan DOES come on with the A/C (e.g. some model years of the Accord), but I don't think the '95 Civic is one of them. The '94 wiring diagram does not show a direct connection between the A/C system and the radiator fan. The only conceivable link would be that the ECU could turn on the rad fan when using the A/C (calls for A/C to turn on go through the ECU and the rad fan relay coil is connected to the ECU in addition to being connected to the thermo switch). I just checked the behavior of my '94 Civic, turning on the A/C causes the condenser fan to turn on, but not the radiator fan. > I measured the new thermo switch by putting an ohmmeter across the terminals > and lowering it into a pan of boiling water. After the switch closed I got 1 [quoted text clipped - 8 lines] > normal. Other times, it seems to be cool, even when the temp setting is over > at max. Could this be due to a bad thermostat or something else? It could be that you don't have a problem at all. This time of year, the radiator fan on my '94 hardly ever comes on (Northern California, so not very cold at all). Caroline (who now uses a different name in this NG) once mentioned that when she did a coolant system bleed, it took a very long time idling before the rad fan came on on her Honda. Signature======================================================= A modest collection of Honda tech info can be found at: http://www.geocities.com/ng_randolph > I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic LX. The > radiator fan does not come on when the AC is switched on (though the > compressor fan works okay). If you've come to the conclusion of a faulty radiator fan circuit based on activating the A/C, listen up. The radiator and condenser fan circuits are isolated from each other. Not all Hondas run both fans simultaneously when using the A/C system. Your year Civic does *not*. They occasionally overlap in operation when normal engine fan cooling is needed with the A/C running. So unless you're having other real issues with the cooling system, save your money... -- Mike 95 Civic "Mike" <mike-r@earthlink.net> wrote in message news:mike-r-1602050310480001@dialup-4.249.168.112.dial1.washington2.level3.n et... > > I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic LX. The > > radiator fan does not come on when the AC is switched on (though the [quoted text clipped - 7 lines] > running. So unless you're having other real issues with the cooling > system, save your money... Actually, I didn't know that. I read otherwise at http://tegger.com/hondafaq/overheating/overheating-index/index.htm : "Start the car and turn on the AC (if so equipped). Both fans (AC radiator and regular radiator) should turn on. If the radiator fan is not turning on, the relay, wiring or fan motor is bad or power is not getting to the fan relay." Anyway, I did have to replace the radiator since it cracked. The only money I (possibly) wasted was installing a new thermo switch ($22) and I learned a little in the process. Good to know that another '95 Civic owner's fan doesn't come on with the AC either. I'll just sit tight and monitor the situation before havnig any more work done. Thanks everyone for your help! > Actually, I didn't know that. I read otherwise at > http://tegger.com/hondafaq/overheating/overheating-index/index.htm : > "Start the car and turn on the AC (if so equipped). Both fans (AC > radiator and regular radiator) should turn on. > If the radiator fan is not turning on, the relay, wiring or fan motor > is bad or power is not getting to the fan relay." Hey Remco, is a revision necessary there? SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ TeGGer® wrote: > > Actually, I didn't know that. I read otherwise at > > http://tegger.com/hondafaq/overheating/overheating-index/index.htm [quoted text clipped - 11 lines] > The Unofficial Honda/Acura FAQ > www.tegger.com/hondafaq/ Tegger, Remco I just checked my 94 Civic(95 engine) and with cold start with a/c on the a/c fan runs but the rad fan does not run. It takes more than 15 min for the engine to warm up enough for the rad fan to come on. (temperature about 60F) My rad fan starts at about half scale on temp gage. Ernie > Tegger, Remco I just checked my 94 Civic(95 engine) > and with cold start with a/c on the a/c fan runs but > the rad fan does not run. It takes more than 15 min > for the engine to warm up enough for the rad fan to > come on. (temperature about 60F) My rad fan starts > at about half scale on temp gage. Like I said... The rad fan will come on only AFTER the coolant temperature has reached about 190F. SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ mike-r@earthlink.net (Mike) wrote in news:mike-r-1602050310480001@dialup-4.249.168.112.dial1.washington2.level 3.net: >> I believe I've got a bad thermo switch/sensor in my 1995 Honda Civic >> LX. The radiator fan does not come on when the AC is switched on [quoted text clipped - 7 lines] > is needed with the A/C running. So unless you're having other real > issues with the cooling system, save your money... Just in case it got missed by the OP the first time, I'm reposting what I said the other day: "Personally, I think you're barking up the wrong tree here. 1 ohm or 8 ohms means nothing. If the temp gauge never gets past 1/3, the rad fan WILL NOT START NO MATTER WHAT. "If you simulated the heavy stop-and-go traffic like I said for AT LEAST 5 MINUTES, and the temp gauge DID NOT RISE, then your engine IS NOT HEATING UP ENOUGH to make the fan come on. "I do believe you have a bad thermostat. Replace with new **OEM** for $20, then report back, BEFORE you spend bigger bucks on the thermoswitch." SignatureTeGGeR? The Unofficial Honda/Acura FAQ www.tegger.com/hondafaq/ > Just in case it got missed by the OP the first time, I'm reposting what I > said the other day: [quoted text clipped - 9 lines] > "I do believe you have a bad thermostat. Replace with new **OEM** for $20, > then report back, BEFORE you spend bigger bucks on the thermoswitch." Yep, got it - thanks Tegger. The thermoswitch was only around $20, I did go ahead and replace it. Based on what you've said, it was probably good and didn't need replacing. If I replace the thermostat I'll be sure and get an OEM unit. But I suspect that the engine is just not getting hot enough. The temp guage goes up to 1/3 shortly after starting up and stays there, never going higher. |
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