Dewitt's Radiator W/dual spals starting when hot
10-04-2011, 06:50 PM
#1
Instructor
Thread Starter
Dewitt's Radiator W/dual spals starting when hot
Long read.....
Recently installed the Dewitt's Aluminum Radiator with dual Spals and automatic sensing unit in my 72, 350, automatic.
The installation went very well and the system works great, hats off to Dewitt's on an outstanding setup! 
Upon completing the upgrade I also installed a new 140 amp alternator and new wiring to handle the load the fans would pull.
Drove the car a few times and everything was perfect!
The other day I took the car out and for the first time drove it, stopped for a few minutes, then got back in the car to go and it wouldn't start! 
The engine temp had reached the point wher the fans came on but the car would not start. The radio, lights, and electric windows all worked! The frustration was setting in 
then remember the amps the fans pull so there was nothing left for the starter! I disconnected the fans and the car fired right up! 
Has anyone else run into this, and if so what did you do to correct it? In researching I've found where the newer cars have a delay where the car will start then cooling fans and accessories will power up. Any one else heard of this or know where you can get a delay like this? What does everyone think about this as a possible fix for my problem?
Recently installed the Dewitt's Aluminum Radiator with dual Spals and automatic sensing unit in my 72, 350, automatic.
The installation went very well and the system works great, hats off to Dewitt's on an outstanding setup! Upon completing the upgrade I also installed a new 140 amp alternator and new wiring to handle the load the fans would pull.Drove the car a few times and everything was perfect!
The other day I took the car out and for the first time drove it, stopped for a few minutes, then got back in the car to go and it wouldn't start! The engine temp had reached the point wher the fans came on but the car would not start. The radio, lights, and electric windows all worked! The frustration was setting in then remember the amps the fans pull so there was nothing left for the starter! I disconnected the fans and the car fired right up! Has anyone else run into this, and if so what did you do to correct it? In researching I've found where the newer cars have a delay where the car will start then cooling fans and accessories will power up. Any one else heard of this or know where you can get a delay like this? What does everyone think about this as a possible fix for my problem?
Last edited by 1972vettman; 10-04-2011 at 06:52 PM.
10-04-2011, 07:13 PM
#2
Race Director
Where did you supply power to the fans from? Mine's hooked up from the alternator, so the starter should have precedence in the circuit. Did you run a wire straight to the battery?
10-04-2011, 10:25 PM
#4
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First off- you should NOT wire the fans to the alternator- the battery is the best place to go- starter terminal is essentially the battery because of the short run of LARGE gauge wire...
In doing so- the battery does a couple things- it stabilized to voltage surges ( like when the fans kick on- they pull a lot of current to start up and then current draw drops back down while running) and filters the the AC ripple coming from the alternator ( really important for computers- MSD-ecus etc...)
It's sort of like this- your bank account is the battery- your alternator is your income and the starter is the house payment...and the fans are child support ...You do not want the mortgage or child support to come directly from your weekly check...
OK...When you hit the starter and the fans were on- did the fans drop in speed?...The starter will pull the power from the battery no matter how the accessories are connected to the power source - there is no precedence!!! Turn on your headlights- and they will dim if you hit the starter IF the starter is actually switching...
I personally think it's a coincidence from what you described- and you might have the beginning of a bad starter....
You can simply put a relay triggered by the starter wire- that breaks the ground on the fan relay....Or get really elaborate and buy a timer circuit ( several of them out there variable up to a minute- mostly used on security systems) and have it delay the fans as soon as it sees a starter signal.
Richard
In doing so- the battery does a couple things- it stabilized to voltage surges ( like when the fans kick on- they pull a lot of current to start up and then current draw drops back down while running) and filters the the AC ripple coming from the alternator ( really important for computers- MSD-ecus etc...)
It's sort of like this- your bank account is the battery- your alternator is your income and the starter is the house payment...and the fans are child support ...You do not want the mortgage or child support to come directly from your weekly check...
OK...When you hit the starter and the fans were on- did the fans drop in speed?...The starter will pull the power from the battery no matter how the accessories are connected to the power source - there is no precedence!!! Turn on your headlights- and they will dim if you hit the starter IF the starter is actually switching...
I personally think it's a coincidence from what you described- and you might have the beginning of a bad starter....
You can simply put a relay triggered by the starter wire- that breaks the ground on the fan relay....Or get really elaborate and buy a timer circuit ( several of them out there variable up to a minute- mostly used on security systems) and have it delay the fans as soon as it sees a starter signal.
Richard
Last edited by Richard454; 10-04-2011 at 10:27 PM.
10-04-2011, 10:47 PM
#5
Melting Slicks
I'm in the process of installing the Dewitts w/ dual Spals in my '73.
Where did you connect the green wire in the fan relay harness? If that wire has power during cranking, it will cause your fans to have power during cranking (if the temperature is warm enough). The solution might be finding a 12V source that does not have power during engine cranking.
DC
Where did you connect the green wire in the fan relay harness? If that wire has power during cranking, it will cause your fans to have power during cranking (if the temperature is warm enough). The solution might be finding a 12V source that does not have power during engine cranking.
DC
Last edited by DC3; 10-04-2011 at 10:50 PM.
10-05-2011, 01:21 AM
#6
Melting Slicks
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St. Jude Donor '08
I used a oil pressure switch between the +12V switched source and the relays, so the fans will not start unless the engine is already started. I did that because I didn't like the idea of having the fans running when ever I turn the ignition key to ON position while the engine is still hot.
10-05-2011, 05:05 AM
#7
Instructor
Thread Starter
I used a oil pressure switch between the +12V switched source and the relays, so the fans will not start unless the engine is already started. I did that because I didn't like the idea of having the fans running when ever I turn the ignition key to ON position while the engine is still hot.
Where did you get the switch? Can you send me a picture and a brief description as to how you did it?
10-05-2011, 05:08 AM
#8
Instructor
Thread Starter
I used a oil pressure switch between the +12V switched source and the relays, so the fans will not start unless the engine is already started. I did that because I didn't like the idea of having the fans running when ever I turn the ignition key to ON position while the engine is still hot.
I'm in the process of installing the Dewitts w/ dual Spals in my '73.
Where did you connect the green wire in the fan relay harness? If that wire has power during cranking, it will cause your fans to have power during cranking (if the temperature is warm enough). The solution might be finding a 12V source that does not have power during engine cranking.
DC
Where did you connect the green wire in the fan relay harness? If that wire has power during cranking, it will cause your fans to have power during cranking (if the temperature is warm enough). The solution might be finding a 12V source that does not have power during engine cranking.
DC
10-06-2011, 12:50 PM
#9
Melting Slicks
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St. Jude Donor '08
Its dark already here and my car is outside, but I'll try to get you a pic.
