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Discussion Starter · #1 ·
Completed a restoration on a 1990 Crx ED9, after being off the road for almost 2 years.
Started it up and bled the system with new coolant, bottom hose on radiator wasn’t hot due to the thermostat not opening for some reason. Decided to remove the thermostat and run without it. Bled the system using a bleeding funnel, to make sure all the trapped air was removed. Temperature went well over half way but the fan wasn’t coming on. Turned the car off, and decided to replace all the temp sensors, 2 on the head and the fan switch on the back of the block. Emptied out and Refilled the coolant a few times, using fresh coolant but the fan was still not coming on.
I then bridged the pins that connect to the fan sensor and the fan came on, which means that the relays aren’t the problem.
Then we tested the continuity of the fan switches, firstly on the old fan switch and it had continuity and then we tested the new fan switch on the car while it was running and for some reason, even when the temp needle was at max, there was no continuity. Swapped the old good switch back in but still no fan - we always bled the system till the temp starts getting near to max.
can anyone suggest something else to try or check out - we're all out of ideas now
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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First things first, check resistance on the wires, need to be close to 0 ohms. Second go get a new pigtail for the fan switch, be sure to use a good set of crimpers and weather proof heat shrink butt connectors, if wires are good and connector is new and still nothing go grab the tstat housing off a 92-95 with the fan switch hole in it and use that location for the fan switch.
As an after thought, are you sure the gauge is reading correctly? An infrared thermometer pointed at the back of the tstat housing will give you a reading to compare with, should be between 170F and 180F before the fan kicks on.
 

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Discussion Starter · #3 ·
First things first, check resistance on the wires, need to be close to 0 ohms. Second go get a new pigtail for the fan switch, be sure to use a good set of crimpers and weather proof heat shrink butt connectors, if wires are good and connector is new and still nothing go grab the tstat housing off a 92-95 with the fan switch hole in it and use that location for the fan switch.
As an after thought, are you sure the gauge is reading correctly? An infrared thermometer pointed at the back of the tstat housing will give you a reading to compare with, should be between 170F and 180F before the fan kicks on.
First things first, check resistance on the wires, need to be close to 0 ohms. Second go get a new pigtail for the fan switch, be sure to use a good set of crimpers and weather proof heat shrink butt connectors, if wires are good and connector is new and still nothing go grab the tstat housing off a 92-95 with the fan switch hole in it and use that location for the fan switch.
As an after thought, are you sure the gauge is reading correctly? An infrared thermometer pointed at the back of the tstat housing will give you a reading to compare with, should be between 170F and 180F before the fan kicks on.
Thanks for the reply.
I checked the resistance in the wires and it was 0 ohms, which is good. I then put the thermostat back in, and bled the system for well over 1hr. The thermostat did open as the bottom hose was nice and hot. There were bubbles of air coming through the funnel even after about an hour. However, the fan did come on eventually thank God- but well after the temperature needle had apparently hit max. We did replace the temp sensor on the head, so I’m thinking could it be a faulty sensor? It just feels that the fan is coming on too late and even then only stays on for about 1-2 minutes - any suggestions welcome 👍🏼
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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I would double check to be sure the gauge is reading accurate, 1-2 minute run times on the fan sounds about right to me, unless its just come back from a few hard pulls. And some of these engines can take 40 minutes or so to reach the fan on set point at an idle.
 

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Discussion Starter · #5 ·
I would double check to be sure the gauge is reading accurate, 1-2 minute run times on the fan sounds about right to me, unless its just come back from a few hard pulls. And some of these engines can take 40 minutes or so to reach the fan on set point at an idle.
So I put the original temperature sensor back, and started the car up. The temp needle didn’t rise past half way even after 30 mins, which I think is normal. The fan also came on, even though the needle was only just below the mid point, is this normal? It must have been a faulty temp sensor, as it would read max just after 15 mins of running at idle. I hope the issue has been solved now.
Many thanks for your input 👍🏼
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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1/3 to 2/5 is the operating range on most Honda temp gauges, so sounds like its just right. Glad it worked out for you 👍
 

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If bridging the fan switch connector made the fan turn on, your wiring and relays are all good.

Replace the fan switch. Even new ones come bad out of the box.

Double check grounds. THat switch has to have a way to travel!

EDIT-- I see your last post, it seems to have been solved. Just keep an eye on it. you can run a cheap LED wire on the fan wiring, and have a light that turns on when the fan is on, as an indicator light of sorts.
 
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