Testing Thermoswitch on 93 1.6
11-07-2009, 06:39 PM
#1
Testing Thermoswitch on 93 1.6
Fortunately there were enough cooling fan threads to make me think that something is wrong with my thermo-switch(s). I want to post because of the plural.
I can ground out the thermo-switch connector and my fans come on. My coolant temp was up to 240F based on Tunerstudio value.
The problem is that I tried two different thermo-switches and both didn't turn on the fans.
What is a good method for testing the thermo-switches? Could I make a simple circuit with a 9v battery, lower the switch into boiling water, and see if I notice voltage drop as the temp climbs?
Based on my searching it appears that it can only be the switches. I couldn't imagine a temp difference of 40F between the front and rear temp sensors unless my thermostat wasn't opening. However it did appear that the coolant was moving when I ran it with the rad cap off.
I can ground out the thermo-switch connector and my fans come on. My coolant temp was up to 240F based on Tunerstudio value.
The problem is that I tried two different thermo-switches and both didn't turn on the fans.
What is a good method for testing the thermo-switches? Could I make a simple circuit with a 9v battery, lower the switch into boiling water, and see if I notice voltage drop as the temp climbs?
Based on my searching it appears that it can only be the switches. I couldn't imagine a temp difference of 40F between the front and rear temp sensors unless my thermostat wasn't opening. However it did appear that the coolant was moving when I ran it with the rad cap off.
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11-07-2009, 07:03 PM
#2
Cpt. Slow
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Not that this helps you, but I believe this is why my fan turns on with a switch. I had my doubts about the thermo switch, so I route 12v to the fan with a relay in the middle, switch turns the relay on/off.
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11-07-2009, 08:20 PM
#3
Fortunately there were enough cooling fan threads to make me think that something is wrong with my thermo-switch(s). I want to post because of the plural.
I can ground out the thermo-switch connector and my fans come on. My coolant temp was up to 240F based on Tunerstudio value.
The problem is that I tried two different thermo-switches and both didn't turn on the fans.
What is a good method for testing the thermo-switches? Could I make a simple circuit with a 9v battery, lower the switch into boiling water, and see if I notice voltage drop as the temp climbs?
Based on my searching it appears that it can only be the switches. I couldn't imagine a temp difference of 40F between the front and rear temp sensors unless my thermostat wasn't opening. However it did appear that the coolant was moving when I ran it with the rad cap off.
I can ground out the thermo-switch connector and my fans come on. My coolant temp was up to 240F based on Tunerstudio value.
The problem is that I tried two different thermo-switches and both didn't turn on the fans.
What is a good method for testing the thermo-switches? Could I make a simple circuit with a 9v battery, lower the switch into boiling water, and see if I notice voltage drop as the temp climbs?
Based on my searching it appears that it can only be the switches. I couldn't imagine a temp difference of 40F between the front and rear temp sensors unless my thermostat wasn't opening. However it did appear that the coolant was moving when I ran it with the rad cap off.
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11-08-2009, 06:34 PM
#4
I bought a new thermo switch and no luck. I then bought another thermostat since mine wasn't opening to my liking. This also didn't work.
It turns out that my fan relay worked when I was diagnosing the problem and that was it. That's right. The one time I used it to troubleshoot the system it worked.
Out of desperation I grounded the thermoswitch again. Nothing but a faint click coming from the box where the fan relay resides. I'll buy a new relay tomorrow. Autozone seems to carry a generic that is $16. Advance has one for $25
It turns out that my fan relay worked when I was diagnosing the problem and that was it. That's right. The one time I used it to troubleshoot the system it worked.
Out of desperation I grounded the thermoswitch again. Nothing but a faint click coming from the box where the fan relay resides. I'll buy a new relay tomorrow. Autozone seems to carry a generic that is $16. Advance has one for $25
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11-09-2009, 08:57 AM
#9
Does anyone know off hand the current draw from the ac and cooling fan? The previous owner wired them in parallel. I am going to replace the 10A relay, but if the current draw exceeds the relay limit then I need to fix that before I start replacing expensive relays.
Last edited by miatauser884; 11-09-2009 at 01:37 PM.
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11-09-2009, 01:37 PM
#11
They are wired parallel. I don't know why I put series. I will edit the post. What amperage are both fans drawing?
5.3 to 6.5 amps from cooling fan: http://www.miata.net/garage/CoolingSystemProblems.html
5.3 to 6.5 amps from cooling fan: http://www.miata.net/garage/CoolingSystemProblems.html
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11-11-2009, 09:54 AM
#12
I ordered a new relay, installed it, then grounded the thermoswitch connector. It works. The relay is listed under the horn relay at advanced auto parts. I'm still concerned that the amperage draw of both fans exceeds the 10A rating for this relay.
Any part numbers for a similar relay except 15A instead of 10A?
Any part numbers for a similar relay except 15A instead of 10A?
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