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Fans not coming on, melted fan relay
#1
So recently I had to replace my battery as it had dead cells.
On hooking up my new battery the fans immediately came on without the ignition on or anything.

Now I have fitted a few years back David McKeen's solid state fan and fan fail relays as well as a button to bypass the otterstat. Occasionally I have lent on the button by accident but it seemed off. David's fan relay also has a 'run on' feature that will keep the fans spinning after you turn off the ignition for a minute or so.
With both of these in mind I waited a minute or so to see if the fans would stop on their own.
Then I smelt the distinct wiff of electrical burning from my relay compartment!
The fan relay was red hot and smoking. I quickly shut down power and let it cool and when I pried the relay out it looked like this:
   

I found my spare, original fan relay and tried it. Everything seemed fine, the fans did not come on without the engine and the relay did not get hot.
I started her up and left her to idle for a while and when she got up to temp the fans kicked in and all seemed well. The only odd thing was that my fan override switch no longer seems to force the fans on, although I could hear a 'click' coming from the relay compartment.
I vowed to investigate further and contact David McKeen to see if he had any ideas.

A few days later I needed to take her for an MOT. On the drive over there I was stuck in some traffic but the fans came on and the temp gauge read normal, in fact when I pulled up to the garage the fans were on. But at some point during testing, with the engine left running,  they turned off and stayed off -resulting in the engine starting to overheat and dumping red-hot water out of the expansion tank overflow. Shock

I cut the power using my battery isolator and checked the relays, seemed fine, not hot. I also in desperation took apart my fan override switch. On re-connecting the battery I wiggled the fan switch a bit and the fans came on! We topped up the water and I made a break for home.
A few miles down the road though I hear a click from the relay compartment and the fans stop again. Toggling and wiggling my fan switch resulted in a audible click from a relay but the fans not turning on. My temp started to climb when in traffic but was able to keep moving and avoid anymore overheating.

So what could be going on? Could my otterstat override switch be dodgy which melted the solid state relay? was the solid state and spare realy both faulty or is something killing them? Is my otterstat up the duff?

Any suggestions on where to look appreciated!
Vin: 4468
DOC No: 758
www.theportlandarms.co.uk
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#2
Check the two electrical connectors on the fans. These sometimes have issues
as they are quite exposed to road spray/water etc.

There can be issues with the earth set up in the relay compartment.
Dave does a upgrade earth ground wire harness.

Are you running the OEM fans or low draw modern fans?
If they are original one or both might be on the way out.
Did you get any warning from the fan fail relay? Flashing fan fail light?

Nick H
DOC 650
Jaguar X-Type
Range Rover Sport SDV6 "Rufus" (Mrs H's motor)
DeLorean DMC 12 Vin#2862

My other hobby...
http://www.lccuk.org.uk/
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#3
It's a simple system. I would first check the otterstat and/or bypass it. My money is on this having failed and caused the other issues.

Chris
Membership Secretary DOC UK
2018's DeLorean event: http://deloreans.co.uk/forum/showthread.php?tid=5715
VIN#15768 Ex VIN#4584 1972 Bond Bug.
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#4
As a 'get you home', in that emergency situation stuck in traffic it will also help enormously if you turn the cabin heater on full and blower motor on full, the cabin heater is basicallly a mini radiator and that normally keeps the temp steady even when the car is standing still running.
Richard Hanlon
Derbyshire
DOC 393

1981 DMC-12 VIN 06126
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#5
Thanks gentlemen for the replies!
Nick H: Still running the original fans and Dave's fan fail relay did not flash the fan fail light. Talking with Dave he thinks I have the breaker still connected between the fan and fan fail relays, that isn't required anymore with his relays, and maybe that has failed. He also thinks one of my fans might be on the way out and is drawing to much current.

Chris: Had the otterstat bypassed (you help me run the cable and switch into the car!) but it wasn't working at all consistently, think the switch might be a bit dodgy so have ordered another one, or it could be the breaker.

Rich: Had though about that but my blower motor barely spins!  Big Grin

Like I say I have been in contact with Dave McKeen who says he will replace the fan relay for free. I am also getting his front relay earth bus kit as recommended by Nick and Dave now does an electronic otterstat as well: https://dm-eng.weebly.com/uploads/2/8/0/...erstat.pdf which might be a good option, leaving the original otterstat as a backup rather than the main solution.


I will make sure the breaker is removed as I think that could be interfering with things

Will test my fans and the connections to it but am considering getting them replaced with the modern low-power-drawing ones. I believe you have done this already on your car Chris? Where did you get yours from? DeloreanGo do a set, as well as a kit with new radiator.
Are there any benefits to replacing the stock radiator if mines not sprung a leak yet or is it a worthwhile upgrade?
Vin: 4468
DOC No: 758
www.theportlandarms.co.uk
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#6
I got my fan set from Josh: http://www.deloreanindustries.com/11-hig...d-upgrade/  however it was before other options were available. I do have a couple of old spare fan motors that your welcome to.
Personally I have changed both rad and fans as my old rad started to leak when I pulled the old fans. As most it's one of Ed's radiators and is very good quality. As you know most things Arran sells are just Ed's anyway. I cant remember if your rad in an original or if it's been replaced.
I have nothing against Dave's modern products, but in my (very) humble opinion it does look like your trying to over-complicate a very simple system. (don't hit me next time we meet) Dodgy  Whilst the OE otterstats are rubbish I think the upgraded version along with an emergency by-pass works fine IMHO.

Chris
Membership Secretary DOC UK
2018's DeLorean event: http://deloreans.co.uk/forum/showthread.php?tid=5715
VIN#15768 Ex VIN#4584 1972 Bond Bug.
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#7
I agree with every word Chris.

I'm still running original fans and radiator, but if either failed I'd upgrade with the Arran / Ed upgrade I have the new style otterstat pipe and screw in switch on the new car and another 'probe in the hose' on the other car. Personally I'd avoid any further electrical gismo's. Keep it simple is my way.
Chris Parnham in Derby  chrisparnham@live.co.uk  07502 143 433
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