Strange electric fan behaviour

[67HEAVEN]

I was on my way to visit my friends at the paint shop this afternoon. I pulled into a Tim Horton's drive thru (as usual ) and shut the engine down so the person on the other end of the squawkbox could hear my order. Then, I pulled to the pickup window and shut 'er down again. I also flipped the electric fans off........too noisy.

When I pulled away, I flipped the fan switch back on, but noticed the temp rising after a few blocks.

"Hmmmmm", says me. :confused

I pulled into a lot and checked. Sure enough the dual Spal fans weren't running.

I was able to scoot home before it got too warm. Once I got into the garage, I checked all the power and ground wires, and the fuses. Everything checked out okay, except that jumping the sending unit to ground would not make the fans come on, as it should.

As I'm scratching my head, the fans suddenly turned on. :eek

Ideas?

P.S. Now that it's cooled down, I jumped the sending unit to ground again, and the fans came on (as they should).

 

[gmjunkie]

I was on my way to visit my friends at the paint shop this afternoon. I pulled into a Tim Horton's drive thru (as usual ) and shut the engine down so the person on the other end of the squawkbox could hear my order. Then, I pulled to the pickup window and shut 'er down again. I also flipped the electric fans off........too noisy.

When I pulled away, I flipped the fan switch back on, but noticed the temp rising after a few blocks.

"Hmmmmm", says me. :confused

I pulled into a lot and checked. Sure enough the dual Spal fans weren't running.

I was able to scoot home before it got too warm. Once I got into the garage, I checked all the power and ground wires, and the fuses. Everything checked out okay, except that jumping the sending unit to ground would not make the fans come on, as it should.

As I'm scratching my head, the fans suddenly turned on. :eek

Ideas?

P.S. Now that it's cooled down, I jumped the sending unit to ground again, and the fans came on (as they should).

I think you've got a ground problem 67 take'm loose and clean them,Grounds do weird stuff!!

 

[JonM]

Did you use compound or Teflon tape on the sending unit?...if you did that will effect the ground.

 

[67HEAVEN]

Did you use compound or Teflon tape on the sending unit?...if you did that will effect the ground.

Hi Jon,

No, I didn't. And, I'm convinced that it's not the sending unit. I ran a jumper between the wire attached to the top of the sending unit and ground, which should trigger the fans. It didn't do so, until they magically turned on later, while I was standing there.

I think Junkie is on to it with the ground. I'm going to replace the wire from the sending unit all the way back through the under dash switch to the fans. I'll take the opportunity to separate the wiring to allow one or both fans to run at the same time. Right now, both run together and can't be switched independently.

Thanks for the input so far.

 

[68Roadster]

I think it's THDS.....Tim Horton Donut Syndrome.....Heaven knew you were stoppin' in for a cup of joe and a glazed with sprinkles and figured you should probably walk off a couple of calories going between the engine compartment and the cockpit....

Put down the donut and back away from the Corvette.....

Seriously though, running a new wire and driving back thru the Tim Horton's drive thru again sounds like proper troubleshooting.....

Sorry Bob.....I couldn't help it! It's just that we aren't used to seeing problems on the finest '67 there is....other than rear bumpers that are .0625" off......

Hope ya get it figured out....thats alot of cubes to be running hot....

 

[IH2LOSE]

Bob Had a simular problem with my 62. Thought it to be the cheap relay that came with the fans .I put in an upgraded higher amprerage relay. One of the Johns posted a link to an electrical supplier I got them from.

Havent had a problem since.

 

[geekinavette]

That does indeed sound like the classic stuck relay symptom. If it acts up again try tapping on the relay with the sensor lead grounded, see if they turn on.

Bill

 

[67HEAVEN]

Bob Had a simular problem with my 62. Thought it to be the cheap relay that came with the fans .I put in an upgraded higher amprerage relay. One of the Johns posted a link to an electrical supplier I got them from.

Havent had a problem since.

Great suggestion, Larry. I'll look for John's post.

 

[richscorvettes]

Bob,

We had a problem with the relays that originally came with the dual Spal fans. It almost looked like they were slowly melting inside the relay case. Be Cool sent me an upgraded higher amp model setup and there were no problems after that. You might be experiencing the same problem.

Rich Lagasse

 

[gmjunkie]

Bob,

We had a problem with the relays that originally came with the dual Spal fans. It almost looked like they were slowly melting inside the relay case. Be Cool sent me an upgraded higher amp model setup and there were no problems after that. You might be experiencing the same problem.

Rich Lagasse

Ya know it could be,I had a problem with the relay on the 37 Chevy Sedan Delivery I built!!:W

 

[John Mcgraw]

Great suggestion, Larry. I'll look for John's post.

Bob,
Here is the link: http://www.partsexpress.com/webpage.cfm?did=7&WebPage_ID=3&catid=47&ObjectGroup_ID=31&CFID=265467&CFTOKEN=69332984

I just don't use anything but these Bosch relays anymore. They are so cheap that it just does not make sense to save a few cents on a cheaper relay.
These guys sell genuine Bosch relays for a fraction of what most retail electronics shops get for the same relay. The have realys clear up to 40 amps!

Regards, John McGraw

 

[67HEAVEN]

Thank you, gentlemen. I'll get right on it.

I'm sure glad it didn't happen half way to Bowling Green.

 

[bossvette]

Thanks for the link.
they must be good they are in Ohio
Just ordered some Bosch relays for my Yellow Truck Project the ones for the fans are genaric and about 15 years old.

 

[BarryK]

Bob,
Here is the link: http://www.partsexpress.com/webpage.cfm?did=7&WebPage_ID=3&catid=47&ObjectGroup_ID=31&CFID=265467&CFTOKEN=69332984

I just don't use anything but these Bosch relays anymore. They are so cheap that it just does not make sense to save a few cents on a cheaper relay.
These guys sell genuine Bosch relays for a fraction of what most retail electronics shops get for the same relay. The have realys clear up to 40 amps!

Regards, John McGraw

I agree with you John.
When I was in the car audio industry at one point i was managing a few hi-end shops and we ONLY used the Bosch relays for the same reason. They were the most reliable, trouble-free ones available so saving a few cents on a cheaper relay wasn't worth it considering the added labor we would have to do if a cheap relay quit on us. In some installations it could be a 4-5 hour teardown just to get to the relay if it quit working so the last thing we wanted was relays quiting!
some of the car security units came included with cheap relays and they went immediatly into the trash and we would use the bosch relays in our stock instead.

 

[Viet Nam Vett]

Very strange.... The relays that came with my Dewitts "Spal" fans are from Spal and have there name on them.. They are rated at 30 amps and are in a water tight plug in case. Also note... The Metal Mounting Tab.. Not Plastic..!!The ones that I see linked and also have seen in the Pep Girls stores are the lower quality crap-ola types.

I have seen those suckers burn up before.. Below is a Pic of the Spal Heavy Duty Water Tight Relay and Plug in assembly...

Is this what you have also Heaven..??

And ..Riddle me this.....There should be 2 relays in use with you fans. One for each fan. Seems odd that they would both crap out at the same time..?????

 

[67HEAVEN]

Is this what you have also Heaven..??

Yes.

And ..Riddle me this.....There should be 2 relays in use with you fans. One for each fan. Seems odd that they would both crap out at the same time..?????

I agree. Seems unlikely, doesn't it.

I was just going to add that thought to this thread, but my mind has been kind of occupied today with another thing going on that is far crazier than this problem. :crazy

And, how was "your" weekend.

 

[Viet Nam Vett]

Yes.



I agree. Seems unlikely, doesn't it.

I was just going to add that thought to this thread, but my mind has been kind of occupied today with another thing going on that is far crazier than this problem. :crazy

And, how was "your" weekend.

Worked on the Vette and changed out the Secondary springs in the Holley.. Made a big diff. Now when you stomp on it ...it Barks louder and quicker with much less lag. I'll post some picks for you tonignt ...my work laptop is down for the count so I can't get on to day. Getting ready to leave for work.


Also ..solved the fan on ..fan off problem. I'll also pass on that info later.

Gotta go..

 

[Viet Nam Vett]

Just got my puter back up at work. Man that sucked..had to re-format the hard drive and start from scratch.

Still a few thinks to put back on here..but it is running like a Brand New ZO6..!! Cleaned all that Sch-Meag-Ma out of the hard drive....

:L

 

[67HEAVEN]

So, now I'm thinking the only thing that makes sense is either a hot or a ground connection problem.

It can't be the relays.....wouldn't cut out and back in at exactly the same time.

It can't be the sending unit......I jumped the top connector to ground, and it made no difference.

I'm going to disconnect the wiring right back to the harness that came with the fans, and re-wire up to the underdash switch and the sending unit.

Then, if I can make the fans come on by jumping the sending unit to ground, I'll take it for a drive and see how reliable it all is.

Probably not until later in the week though. Things are kinda weirded out around here right now.

 

[Viet Nam Vett]

So, now I'm thinking the only thing that makes sense is either a hot or a ground connection problem.

It can't be the relays.....wouldn't cut out and back in at exactly the same time.

It can't be the sending unit......I jumped the top connector to ground, and it made no difference.

I'm going to disconnect the wiring right back to the harness that came with the fans, and re-wire up to the underdash switch and the sending unit.

Then, if I can make the fans come on by jumping the sending unit to ground, I'll take it for a drive and see how reliable it all is.

Probably not until later in the week though. Things are kinda weirded out around here right now.

Here's the deal...my system is wired as follows.... Note..I will leave out the trick stuff that 's in my system as it won't apply to your set up....

Power is pulled from the Horn Relay Buss Positive Connection.

It then is split to the 2..... 30 amp in line fuses.

Each fuse feeds the Positive input lead of each of the 2 fan relays

Each Positive Output lead from the relays feeds the fan positive input lead of the fan.

-------------------------------------------------------------------------

The Grounds for both fans are tied together from the fans and run as one main ground.

Now here's the important part.... Either ground the fan master ground wire...( The one where both fan wires have been tied together).. to the 502's Block which should have the Neg Battery cable also attached.

Or..run a Number 8 Gauge wire to the fan shroud from the 502's block and ground the Main fan ground their.

Now you can do what ever you want with the Sensor ground wire from the relay coils.

Important thing here is that ..Positive Power is pulled from the Horn Relay Buss Bar..
Which is the Center of the Charging Universe. Remember..your Alternator is running the Fans not the battery. Also this is the Sensing point for the alternator voltage Regulator. I assume that you have an Alternator with a built in Voltage Regulator

When the fans pull in ..they tell the Alternator to pick up the out put since the sensing point is the same as the fan pull off point.

Just make sure your ground connections are to bare metal. After you attach your wires to ground you can paint then over with 1613.


Ok..time to go home....I'll post some pic's latter..