I recently bought a 1991 Honda Acty. Got it home and all seemed well but after driving it around I noticed that the temperature gage wasn't going up. I looked under the truck at the sensor to find that the sensor was cut and the wire grounded! Looking around it seemed that the correct sensor was $100+ from Japan with no one this side of the world selling it. I decided to try a generic one before shelling out the big bucks. I found this one https://www.amazon.com/gp/product/B009HW44F4/ref=oh_aui_detailpage_o05_s01?ie=UTF8&psc=1 for about $17 with prime shipping. The threads for the new ones didn't thread into the exhaust so I put the old nut back in and put the sensor through and pinned it against the brake line. It's not the best and leaks out a bit but it works and it's a heck of a lot cheaper than buying the actual sensor. I've looked through the service manual but I can't figure out if the sensor is just for the temp gauge or if it controls anything. Does anyone know?
Temperature gauge for the coolant is different from the temperature sensor for the cat. For the coolant gauge on my Acty it takes also a long time till it moves, usually some miles that it starts to move and then it goes up to just before 12 o-clock where it stays always, no matter how hot the climate is, as we have the aux fan which will kick in, even when the engine is stopped, sometimes in hot summer the aux fan switches on to cool down to avoid fuel vaporizing in the carb and fuel lines inside engine bay. The temp sensor on the cat is a different story, actually you could have left is disconnected. I know that from my BMW E32 750iL from 1988 Japan spec.,in those years it was mandatory to have a catalysator temperature sensor. On my BMW the sensors (has 2 cats for the V12 engine) are connected to a relay, and this relay gives a warning signal in case the cat has reached a temperature of 870 degrees Celsius = glowing hot, then a warning signal shows up in the check control of the cluster. This was mandatory in those days, should prevent from fires from glowing cats on cars parked on grass or areas which can burn easily. Even when I switch on the ignition this warning sign comes up every time, it is a test/check if the warning works, will go out after 2 seconds. This cat/exhaust temperature feeler is not connected to the engine control, just a warning. Here pics of the relay on my BMW, located under the rear seat and the sensors in the exhaust pipes
Good to know! Yours has an actual coolant temp gauge? Mine just has the exhaust temperature one. It would be nice to have a coolant temp gauge.
I think there is a mixup of some sort. If you have a temp gauge in the instrument panel, it is coolant temperature. The Cat temp would be just a warning light somewhere on the instrument panel face. Fred
Yes, I also assume he mixes up, the gauge is coolant, the exhaust temp sensor has only a red warning light, my HA3 truck is from 1997 and the instrument cluster has a coolant temperature gauge on the left side. Just tested today, we have here today in Japan 7 degree C = 44 degree F, started cold engine, after about 2 km the indicator started to move slowly, after about 4-5 km it was at running temperature = some mm before the 12 o' clock = left of the middle. samples of clusters from the Japanese auction house HA4 https://page.auctions.yahoo.co.jp/jp/auction/f260019766 HM1 / HM2 https://page.auctions.yahoo.co.jp/jp/auction/h305095615 HA6 / HA 7 https://page.auctions.yahoo.co.jp/jp/auction/r235650462 https://page.auctions.yahoo.co.jp/jp/auction/l336266767 HH5 https://page.auctions.yahoo.co.jp/jp/auction/d274464311 Here I have set up the search for all Honda Acty parts in Yahoo Japan auctions, that is the biggest auction house for such stuff, more than 27000 items for the Acty at the moment https://auctions.yahoo.co.jp/search...tab_ex=commerce&fixed=0&ei=UTF-8&xargs=35&b=1 Here in English from a company which can bid for you and arranges shipping to overseas http://yahoo.aleado.com/ auction agent and order service , Japan deputy services for Bidding on Japan auction & import from Japanese online shop. Yahoo how to buy http://yahoo.aleado.com/buy_en.htm fees are reasonable: FOR OVERSEAS CUSTOMER , Fees and charges in case of international mail delivery from Japan http://yahoo.aleado.com/aleado_price_en.htm If you want a coolant temperature gauge, buy aftermarket, cheaper, maybe you can connect it to the coolant temperature sensor for the engine control, but on the other hand the temp sensors for the engine control and for the cluster gauge are quite different. Usually there is a sensor for the engine control and an additional for the cluster gauge. The engine control module needs a superfast and exact signal, while the one for the cluster is just the opposite, superslow and like a guess-o-meter. On my 1988 BMW it works like this Temperature indication on the BMW is not linear, they call it 'tableau', basically the indicatior at 12 o'clock = in the middle between cold and hot can mean everything between roughly 75-110 degree Celsius. Everything in between 75-110 is just 12 o'clock. Plus/ minus 1-2 mm to the right or left (deviation cased by the parts installed). The analog signal ist processed in the instrument cluster and compared with data in the coding plug. A corresponding signal is sent to the instrument. Five temperature support values are stored in the coding plug. Exceeding the temperature limit stored in the coding plug will additionally send corresponding warning information to the check control and display it there. That is written and shown here on page 4 of the instrument cluster check control training reference book http://www.e38.org/e32/BMW_pdfs/INST_info.pdf
Thank you for the reply. Good to know. I thought that the exhaust sensor was the temp that drove the gauge. I've taken it on a few 5-10 mile drives here in Michigan where it's about 30f and it has only gone up to operating temp once and shortly after went back down. My reserve tank is full of coolant. Maybe my thermostat is stuck open.
Then you have to find out what the problem is, thermostat, the temp sensor. Running at too low temperature is not good for the engine, optimal condition is operating temperature, otherwise more engine wear and higher fuel consumption. Is the heater system heating up or not? But I would start with the thermostat, maybe you can get locally one from the aftermarket. That is a wear part and has to be changed anyway every few years. Original is Honda Acty Thermostat 19300-P36-003 , Replacement Thermostat for all Honda Acty Series E05A Engines. HA1, HA2, HH1, HH2, HA3, HA4, HA5, HH3, HH4 E07A Engines. Alt PN 19300-PN3-003. Note: Gasket Not included, Order Separately Looks like this, also click on the pic of the o-ring, there the original Honda # is shown https://minkara.carview.co.jp/userid/469504/car/391515/7708098/parts.aspx aftermarket from China http://www.miparts.com/oem/19300-P36-003 here shown where it all fits on the ERA site https://ecom.eraspares.com/EC/TabelloneCategoria.asp?IdCategoria=600&Pagina=76 ERA 350536, diameter 48 and 28mm, opening temperature 78 degree Celsius., comparable numbers: HONDA 19300-P36-003, ( 19300P36003 ), 19300-PN3-003, ( 19300PN3003 ), 19300-PN3-004, ( 19300PN3004 ), 19300-PN4-003, ( 19300PN4003 ), 19300-PN4-004, ( 19300PN4004 ) MAZDA 1N03-15-171, ( 1N0315171 ), 1N04-15-171, ( 1N0415171 ), 1N05-15-171, ( 1N0515171 ) TOYOTA 90916-03082, ( 9091603082 ), 90916-03112, ( 9091603112 ) VALEO 820515, ( 820515 ) also used in TOYOTA PASEO at Yokohama Motors Yen 2480 = approx $ 25, that is a good price, just checked other shops in Japan http://yokohamamotors.net/page61.html In case you have a contactless infrared thermometer that would help you to check without removing any parts, just point at the radiator, the coolant hoses etc, I use that often, something like this from HF https://www.harborfreight.com/infrared-thermometer-93984.html there are smaller and cheaper ones available. As for the temp sensor for the gauge I do not have the test data, for my BMW it is a NTC which has 2.5 kohm at 20 degree Celsius. Maybe someohere here has the actual test data for the Acty sensor. Also check the wiring and the contacts on the sensor
I have a infrared thermometer. I'll have to check it on the truck tomorrow. It has been blowing heat but pointing the thermometer at things seems like a good place to start. I'll get at it tomorrow and post what I find.
Didn't get the thermometer out but sitting idling it will warm up and reach operating temperature. Once you start moving thought it almost goes all the way back down to cold.
Then it is definitely the thermostat, which is stuck in open position. Had the same last year on my 1998 BMW E36 M3, when idling or in traffic jam it went to operating temperature and when I starting driving temp went down due to the air coming thru the radiator. Thermostat should be in same position after engine came to operating temperature, even in hot summer here in Japan with temperatures up to 35-40 degree Celsius the gauge needle is steady on my Acty. If necessary, the electric aux fan chimes in and assists cooling, but not very often. Get a new thermostat and replace the old one.
Agree with shogun. Classic symptom of stuck open thermostat or now & then some people have the thought that removing the thermostat is a better idea when in fact they are ruining their engine from running at improper temperature range. You may find that sometime in the past, it has been removed. Fred
Next paycheck I'll get a new thermostat on the way. Why would you want to run the truck without a thermostat? Even driving the truck like I stole it petal to the metal it won't warm up while it's moving. lol
People pull thermostats because they live in hot climates and think it will help to pull it out. Frequently that is a new problem. Because, the flow is so fast through the radiator, that there isn’t enough time for the heat to exchange. The other reason is the one they have, and they pull it out other than buy another. Race vehicles, typically have restrictor plates instead of thermostats. The plate has no moving parts, and can’t fail at inopportune moments.
Just a quick update. Thanks for all your help. Got the thermostat replaced and all seems to be well. Warms up and runs a lot better. Bleading the air out wasn't fun but it wasn't too bad. Thank you all for helping me learn.
For future reference: Honda Acty thermostats can be purchased at O'reilly Auto Parts. The part number is 3758 and costs about $6. I replaced one on a 1990 Acty.
good find, here some more details for future reference: Murray Plus Thermostat Part # 3758 Line: MCS Unit of Measure: Each UPC: # 799304837589 Temperature (Deg F): 180 Degree Flange Diameter (In): 1-7/8 Inch Height (In): 2-1/8 Inch Bypass Flange Diameter (In): 1-1/16 Inch Flange Thickness (In): 0.05 Inch Gasket Or Seal Included: No Jiggle Pin Included: No Material: Stainless Steel, Copper Height Between Flanges (In): 1-3/8 Inch
