Radiator fans

[Trstno1]

Does anyone know how to test the rad fans just to see if they actually work? I'm not sure that I have ever had it running long enough to get up to temp. Do I just need to jumper the two pins on the otterstat with the ignition on? If so, and the fans don't come on how do I know if the otterstat is operating correctly?

[krs09]

Does anyone know how to test the rad fans just to see if they actually work? I'm not sure that I have ever had it running long enough to get up to temp. Do I just need to jumper the two pins on the otterstat with the ignition on? If so, and the fans don't come on how do I know if the otterstat is operating correctly?

When I got my car the fans were disconnected from the otterstat and jumped together (otterstat was gone and the pipe was welded shut), the fans came on and stayed on when turning the key. After replacing the fans (toby's DMCNW) and the otterstat all was good. If you jump the wires with stock fans and get nothing I'll bet you need new fans just to start. Otterstat is only a couple of bucks I would just get a new one and be done with it.

[Trstno1]

Ok, I jumpered the wires from the otterstat and the fans came on. Is there a way to test the otterstat with a meter for function? Obviously if the two pins have continuity when the otterstat is cold it would need replaced. But is there any other test that one could run to see if it works other than running the vehicle up to temp? At rest should the otterstat pins be tested as an open load or a certain resistance?

[Trstno1]

Right now the otterstat measures at 4.8 M ohms when cold between the two pins. Do the otterstat readings control the temp gauge in the car or just the operation of the rad fans? Sorry.....newbie here.

[sdg3205]

Ok, I jumpered the wires from the otterstat and the fans came on. Is there a way to test the otterstat with a meter for function? Obviously if the two pins have continuity when the otterstat is cold it would need replaced. But is there any other test that one could run to see if it works other than running the vehicle up to temp? At rest should the otterstat pins be tested as an open load or a certain resistance?

I think thats backwards - continuity when hot (switch closed).

It's a make or break connections, like a light switch.

[DMCMW Dave]

I think thats backwards - continuity when hot (switch closed).

It's a make or break connections, like a light switch.

You can take it out of the car, put an ohm meter on it (will read wide open), warm it up to 200 degrees and see of it closes (zero ohms). Kind of a lot of work.

[dustybarn]

Right now the otterstat measures at 4.8 M ohms when cold between the two pins. Do the otterstat readings control the temp gauge in the car or just the operation of the rad fans? Sorry.....newbie here.

The otterstat controls only the fans. Since jumpering the wires caused the fans to run, there's a pretty good chance the otterstat is bad (they are notoriously failure-prone).

Make sure that the otterstat pipe is oriented so that the otterstat is on the bottom. This ensures that the otterstat is immersed in liquid coolant, and is not insulated in a vapor pocket.

[Trstno1]

The otterstat controls only the fans. Since jumpering the wires caused the fans to run, there's a pretty good chance the otterstat is bad (they are notoriously failure-prone).

Make sure that the otterstat pipe is oriented so that the otterstat is on the bottom. This ensures that the otterstat is immersed in liquid coolant, and is not insulated in a vapor pocket.

Yes, The otterstat is mounted so that the terminals are pointed down. I guess the other sensor that may be causing the issue is the coolant temperature switch. Since I dont have any means of actually testing the temp of the coolant, I suppose I should just get a replacement of each......

[Rich]

Not quite straight on the names of the components that are - and are not - in this circuit. See boldface comments:


Yes, The otterstat is mounted so that the terminals are pointed down. Good, so the Otterstat is seeing coolant, which doesn't mean it works it just means that the tee it sits in is oriented correctly. I guess the other sensor that may be causing the issue is the coolant temperature switch. It is a bit confusing but what we call the Otterstat IS the coolant temp switch for the rad fan circuit. Since I dont have any means of actually testing the temp of the coolant, I suppose I should just get a replacement of each......

Assuming the coolant in the pipe is getting hot enough to kick on a good Otterstat the only part you need is a new/good Otterstat. The book says the Otterstat switch-closed temp is ~207F/97C in case you feel like testing yours off the car as Dave described.

[Trstno1]

Not quite straight on the names of the components that are - and are not - in this circuit. See boldface comments:



Assuming the coolant in the pipe is getting hot enough to kick on a good Otterstat the only part you need is a new/good Otterstat. The book says the Otterstat switch-closed temp is ~207F/97C in case you feel like testing yours off the car as Dave described.

Sounds good, I'll test things tomorrow. Thanks!!

[DMCMW Dave]

Yes, The otterstat is mounted so that the terminals are pointed down. I guess the other sensor that may be causing the issue is the coolant temperature switch. Since I dont have any means of actually testing the temp of the coolant, I suppose I should just get a replacement of each......

The coolant temp switch in the engine has nothing to do with the fans. It enriches the fuel mixture below about 30F. Actually it is electrically parallel with the full throttle microswitch.

Besides, that one is a huge PITA to replace.

[hmcelraft]

http://www.harborfreight.com/Non-Contact-Infrared-Thermometer-With-Laser-Targeting-69465-8905.html?ccdenc=eyJjb2RlIjoiNzc0NjAxNjIiLCJza3UiO iI2OTQ2NSIsImlzIjoiMjUuOTkiLCJwcm9kdWN0X2lk%0D%0AI joiODkwNSJ9%0D%0A&utm_medium=email&utm_campaign=0615a&utm_source=1011&cid=mEmail_s1011_c0615a

This is a great tool to have

[Timebender]

Dumb question- where is the otterstat located, as I know my fans aren't coming on.

[Trstno1]

The coolant temp switch in the engine has nothing to do with the fans. It enriches the fuel mixture below about 30F. Actually it is electrically parallel with the full throttle microswitch.

Besides, that one is a huge PITA to replace.

Does the coolant temp switch also run the temp gauge in the car?

[sdg3205]

Dumb question- where is the otterstat located, as I know my fans aren't coming on.

Left/driver side of the engine, next to the frame you'll see an aluminum pipe - look on the underside. Should have 2 spade terminals connected to it

[sdg3205]

Does the coolant temp switch also run the temp gauge in the car?

No, the temperature sender is on the right, forward side of the INSIDE of the block - uses a ring terminal.

[Lou and "Boo"]

You can take it out of the car, put an ohm meter on it (will read wide open), warm it up to 200 degrees and see of it closes (zero ohms). Kind of a lot of work.

Definitely a lot of work for a fifteen dollar part NOS from Houston.

[Timebender]

Left/driver side of the engine, next to the frame you'll see an aluminum pipe - look on the underside. Should have 2 spade terminals connected to it
Got it. Looked it up too after I posted that as well. Thanks! I'll have to take a look when it comes back from DMC CA.