Electric Fan Relay Issues?
 

I have a Hayden 3647 electric fan relay – the probe style. I’m running a 383 stroker.

When I bought the truck the probe was disconnected and the electric fan ran constantly. Temp was a solid 160. I reinstalled the probe and adjusted the temp up to about 190. The truck runs in the 175 – 195 range most of the time. Most of the time... When I drive to work I take the highway. I pull off the highway and right into my parking garage. By the time I park, my temperature is over 220 and rising. I shut the truck off as soon as I parked so I couldn’t tell if the fan was working when I was driving in the garage. I did turn the key back on and the fan turned on.

Any ideas why this would be? I’m starting to question the operation of the relay, but before I go spending money, I want to make sure that I’m thinking this through. Thanks in advance for advice.

Re: Electric Fan Relay Issues?
 

Isett,

Sounds to me like there's a lag between the engine and the probe -- in otherwords that the probe doesn't react very quickly to rapid engine temp changes like might happen when you take an engine that's been running at high speed and suddenly remove the fast air flow.

If that's the case, then it might be that the probe is being cooled by passive air flow? Can you move it to someplace that won't get air when the truck is moving?

B

Re: Electric Fan Relay Issues?
 

Not on my truck but I put one on my car. I drilled a hole then brazed a nut (1.5 X 18mm?) on a piece of muffler pipe and got a flush to the bottom of the nut type sending unit from a Honda. I cut the lower rad hose and after installing the pipe put the spring back in to prevent hose collapse. Works great and only comes on when the car idles for a while like when trying to get into a car show or getting it parked in the garage. I wired it hot so key position does not prevent it from coming on.

Re: Electric Fan Relay Issues?
 

Where is the probe installed I had mine installed in the rear of the intake manifold and it would not turn on. It started working when I installed it into a port in my water neck.

Re: Electric Fan Relay Issues?
 

When you see the cars in the junk yards most of the sensors are close to where the coolant enters the engine. If the radiator hasn't cooled it enough then the fan comes on.

Some say the sensor should be after the coolant leaves the engine but before it enters the radiator. Foolish thinking, give the radiator a chance to do the job on its own.

Re: Electric Fan Relay Issues?
 

I just got mine. Thay said to put it in the head or in the front of the intake.

Re: Electric Fan Relay Issues?
 

If by "probe" you mean one of those things that you stick through the radiator core, get rid of it and get a sensor that screws into a cylinder head or the top radiator tank or somewhere that it can measure the actual water temp.

Re: Electric Fan Relay Issues?
 

Let us know what you did to fix it when you do.

Re: Electric Fan Relay Issues?
 

It's a 3" aluminum peg - about the width of pen. It sits in between the fins in the radiator. I have it tucked in the upper corner near the battery so it shouldn't be getting much airflow to change to air temp.

I've got a couple of things on my list. I'm going to flush the cooling system and replace the thermostat to start. I'm also going to get an led indicator light so I can see when the fan is running. I'll start there and keep a close eye on things.

Thank you for all of the suggestions.

Re: Electric Fan Relay Issues?
 

If you move it to the bottom of the radiator close to the exit you will see an improvement in fan control performance. I'd be very surprised if you reported back to the contrary.

Re: Electric Fan Relay Issues?
 

Imo i would get rid of the probe and use something else.