After Run Pump Relay Needed

I was trying to create a circuit for a after run pump so that when the vehicles Ignition switch is off and the temperature sensor is above a certain temp, the cooling fan kicks on as well as the pump. An Audi 5000 has this system, I think using a similar system would be my best bet. (http://forums.quattroworld.com/s4s6/msgs/21503.phtml). I plan on keeping a 10 to 15 minute timer so that it will not kill the battery. I had 3 initial ideas either use a 5000 relay which is prepared for the system but they are quite expensive, also they are electronic and are known to fail. Using a saab 9000 defroster relay has a built in timer 10 minutes and it activates. Unfortunately i can't see how i could make it work when the key is turned off nor find if it is normally open or closed. http://www.saabnet.com/tsn/faq/9000wiringdiagrams.pdf Page 18 Workings of relay This relay I am unsure if it is NO or NC Or Get a hella relay, which allows me to choose the time and how it may work 996152131 delay on release 996152151 delay on operate http://www.hella.com/hella-us/assets/media/HINC_Electrics_Catalog.pdf Page 57 Any ideas?

Why do you want that? Are you having overflow or boil problems, or blowing headgaskets or other issues? If not I wouldn't worry about it. As soon as the engine stops its combustion chamber begins to cool and that is the most temperature stressed engine part. Other parts may heat up but that is normal and non damaging. It's different with competition and non-(mechanical)-thermostat systems using electric water pumps but they merely need a timed circuit triggered by IGN off and optionally an initial kick-off thermostat (thermistor) enabling signal.

Running a cooling fan with the ignition off will drain your battery in short order.

oldspark wrote: Why do you want that? Are you having overflow or boil problems, or blowing headgaskets or other issues? If not I wouldn't worry about it. As soon as the engine stops its combustion chamber begins to cool and that is the most temperature stressed engine part. Other parts may heat up but that is normal and non damaging. It's different with competition and non-(mechanical)-thermostat systems using electric water pumps but they merely need a timed circuit triggered by IGN off and optionally an initial kick-off thermostat (thermistor) enabling signal.

The vehicle is a 1980 fiat spider you actually have helped me through wiring a few items on it and relay questions i had in the past. They are very known for overheating or running a little hot, I have had a turbo on this car and also used a bigger aluminum radiator and made the cooling system a little better as well as a oil cooler but the engine still does suffer from a bit of heat soak. This system is implemented on the audi/vw turbo vehicles for many years and still use this to date, to improve the life of the engine/turbo. I would like to add this feature to help with the overall life of the components and reduce strain. Since posting i believe my best bet may be using a hella relay that way i have some adjust ability in time and NC and NO for how it is wired.

howie ll wrote: Running a cooling fan with the ignition off will drain your battery in short order.

Yes it will but that's why i need a relay which has an internal timer set for 10 or 15min which will only turn on if the temperature switch is also above a certain temperature other then that it the fan and pump will not turn on. While putting a fan on 12v for 10 to 15 min and also a pump will possibly weaken a battery, this system uses a resistor to slow down the fan and just have it spin to cool as it circulates. So i have looked at the diagrams and they are set up quite different and I am unsure what should be the input into the timer. I would presume that terminal 15 is the ignition switch terminal 31 ground terminal 30 use the switch but instead of using + flip it to - terminal 87A would ground the fan relay, afterrun pump Also I would not use terminal 87 I would like to run a similar setup to the orginial, The hella relay is set up in this configuration The original fan relay uses a - input trigger for relay.

Excellent! My apologies, as usual I did not note who the poster was and more often than not I see so many car projects like this that are so misguided or false. [Anyone for fuel polarisers; or mobile phone chargers to improve EMS & performance; or resistors - maybe even their hi-tech voltage-regulator version - to trick EMSs into better performance LOL (which would blow engines if they actually worked for leaner mixtures!)...? ] But cool - you said it - engine soak. And as I recall some of those Italians could suffer badly. Incidentally, I suppose you have the normal crank driven water pump... you haven't removed the engine's (mechanical) thermostat and fitted an electric system? If the Hella is a direct plugin for the fan relay (with added small terminal wiring) then I'd be tempted. My only concern would be if it draws current with IGN off - ie, from what I've seen such relays tend to use 555 timers and they have their 10mA standby draw. That's no problem for their fuel pump control relays (missing pulse aka tachometric 555 circuits) because they are powered via IGN +12V, but not seeing in the above relay schematic what timing circuit is used nor how it is powered after IGN off... But I haven't examined your detail. I'd even have to look up whether 15 & 31 are IGN etc!     However I'd be tempted to use a DEI 528T or similar. That too has its 555 10mA drain but it should be easy having it power itself off tho that might require an extra relay (and 528T) if you want the fan to come on if whatever temp sensor hits your desired fan-on threshold within x-minutes of engine/IGN turn off. My main attraction for the 528T is the use of available parts etc and the NON-use of specialised relays. (I prefer standard (SPDT) relays with external controls, even external quenching diodes etc.)    FYI - I'm looking at a similar 528T set up for bach939 in adding additional accessory to door locking. That's to use 528Ts but I need to check 555 (& 528T) trigger behavior wrt to power-on timing, etc. Are you after stealth? IE - are you seeking originality in looks etc? My solution to that was the use of a PICAXE 08 (08M2) which are 8-pin devices the same size as a 555 timer but without the need for larger timing capacitors etc. Excluding their output MOSFETs etc they could even be concealed within wiring - and reprogrammed without removal or direct access (run their programming input wire to somewhere suitable). And the 08M2's standby current is far less than leakage current of automotive batteries so even fulltime powering is not an issue. That does require the usual circuit construction ability (soldering etc) plus a serial interface & PC or maybe smartphone etc for programming plus the associated learning curve. However the latter is greatly simplified by the plethora of existing web projects (ie - copy & paste code) and once established is far easier than working with traditional circuitry... there is no need to overcome tricky electronic designs nor change or adjust componentry; just reprogram the new function or change parameters. One standard 08M2 PCB or circuit can handle so many functions - ie include onboard LM7805 voltahe regulator (TO-92 package); 2 programming resistors; one MOSFET output; other inputs & outputs with provision for a series & pull up or down resistors & filter cap etc and a MOSFET for outputs. IMO the 08M2 is perfect. It can be an add-on that uses the existing fan relay (probably without diodes if ground-switched sensors/controllers are used) and overcomes all problems... EG - switch or keep the fan on if whatever sensors are above a certain temp even with IGN off unless IGN has not been on for 5 minutes, and do not run for more than 3 minutes or if battery voltage is less than 12.4V... and BTW - flash that dash warning if the battery voltage is less than 13.4V with engine running else 12.6V & quicker if it's less than 12.4V (or get my battery monitoring program to text the dash's alphanumneric display next time the IGN key is inserted or turned on..). That's merely a bit of brainstorming in case you are interested. Otherwise it's back to traditional physical circuit implementations. And that's pending for me (I'm avoiding circuit DIYs like 555s & 08M2s for bach939).

Still has the mechanical water pump much more reliable then anything electronic I've seen, god bless anyone that uses those bmw electronic thermostats or water pumps which fail every 80k, if not before. I really like the 528T but it only seems to be adjustable up to 90 seconds so i would probably still need a relay such as the hella relay with a 15min timer.I think i can make the hella relay work i emailed hella to see what they say about the timer if it needs a positive or negative and that way i can see how to do it if there nice maybe they might give me and idea. Also hows the triumph motorcycle i believe when we spoke about the fiats fuses you said it had the same type of fuses. Always burns where you can't see it.

Hi, Using DIN 72552, terminal 15 would be positive ignition voltage, 30 is battery, 31 is ground. And some more searching on the Hella relay found this: http://www.4x4ham.com/showthread.php?5002-12v-Delayed-turn-off-or-turn-off-%28howto%29 The 528T can be modified for longer operation times by changing component values. Mark

I agree with Ween - modify the 528T. (In principle easy - to double the delay solder another identical timing cap across the existing one - ie, no track cutting etc. Otherwise insert a extra resistor in series with the timing resistor(s).) A 15 minute delay could use f.ex a 1,000uF cap and total timing resistance (R1 +R2) of ~1M. That'd be my preference to avoid using fancy relays. Otherwise RC MOSFET circuits where the operational logic required determines how it is implemented, but the 555 may be more versatile.

Ween wrote: Hi, Using DIN 72552, terminal 15 would be positive ignition voltage, 30 is battery, 31 is ground. And some more searching on the Hella relay found this: http://www.4x4ham.com/showthread.php?5002-12v-Delayed-turn-off-or-turn-off-%28howto%29 The 528T can be modified for longer operation times by changing component values. Mark

I asked hella if the timer input can be reversed with a negative signal and have a positive on the other side or if they had an option on something else they make. It probably is a no but I was curious. I like the 528T and i am not going against what you guys are saying about it, but in terms of longevity and overall reliability wouldn't a hella style relay perform overall better and be simpler then the 528T.    What makes the 528T a better choice? This is purely for my curiosity.

Probably no difference except price. Both good quality and no problems with the 528t over the years. I've had one Bosch (Porsche) and one Hella (UK Ford Escort RS) fuel pump primer relays fail though.