Folks need some help,
In the middle of installing a new radiator and puller fans,
The old set up had diodes on the hot side to the Meriah fans
The 3rd fan being a puller had a diode on the ground?
Are these nessasary and has anyone had luck without these.

Thanks in advance
Mark

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Original Post
I believe the reason for the diodes is to keep the fans from acting like a generator. Without them, the fans can cause the car to run on because the keep power to the ignition system.

Someone will be able to explain this better.
Say Mark, the rad installation is looking good.

Here's the situation. With the oem wiring, when you turn the ignition switch to off, the fans & ignition are disconnected from the battery, but they remain connected to one another. The fan motors act as generators & generate enough current to keep the engine running.

If you install fan relays as detailed in the drawing below, this situation will not exist & the diodes shall not be needed.

cowboy from hell

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George,
Thanks a bunch, this will really help with the setup, will post as the project moves forward,

Mark

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Last edited by sickcat
quote:
Originally posted by george pence:
Say Mark, the rad installation is looking good.

Here's the situation. With the oem wiring, when you turn the ignition switch to off, the fans & ignition are disconnected from the battery, but they remain connected to one another. The fan motors act as generators & generate enough current to keep the engine running.

If you install fan relays as detailed in the drawing below, this situation will not exist & the diodes shall not be needed.

cowboy from hell



George, how would I eliminate the problem with stock fans?
quote:
Originally posted by george pence:
Doug, install the relay mod as per the wiring diagram.

cowboy from hell


Your diagram does not show the original relays.
Do I replace them with generic relays?

If I do, what original wires go to the new relays and to what terminals?

You indicate all new wires and I presume that is because you did this diagram for a new "SPST" fan replacement?

Sorry George. In this case I need to be extra electrically challenged.
I need to be lead by the hand on this one.
quote:
Originally posted by PanteraDoug:
...Your diagram does not show the original relays. Do I replace them with generic relays?...


Yes. Replace them with DIN style (European) relays. They are available at most auto parts stores, in current ratings up to 50 amps DC. SPST, continuous duty. You can mount them in the oem location, and some relays have a little mounting tab on top for that purpose.

quote:
Originally posted by PanteraDoug:
...If I do, what original wires go to the new relays and to what terminals?...


The wires on the drawing marked pink are the oem wires. They run from the fuse box forward to the oem relays, where they supply both the relay coils and the fan motors. All of the original wiring downstream of the pink wires can be removed from the vehicle. The oem pink wires will connect to terminals #86 of the new relays.

quote:
Originally posted by PanteraDoug:
You indicate all new wires and I presume that is because you did this diagram for a new "SPST" fan replacement?...


The diagram is drawn for any installation involving higher power (amperage) motors than the oem motors. Which should fit the description for EVERY Pantera.

quote:
Originally posted by PanteraDoug:
...I need to be lead by the hand on this one...


No problem my friend, I'm honored to be able to help.

cowboy from hell
quote:
Originally posted by george pence:
quote:
Originally posted by PanteraDoug:
...Your diagram does not show the original relays. Do I replace them with generic relays?...


Yes. Replace them with DIN style (European) relays. They are available at most auto parts stores, in current ratings up to 50 amps DC. SPST, continuous duty. You can mount them in the oem location, and some relays have a little mounting tab on top for that purpose.

quote:
Originally posted by PanteraDoug:
...If I do, what original wires go to the new relays and to what terminals?...


The wires on the drawing marked pink are the oem wires. They run from the fuse box forward to the oem relays, where they supply both the relay coils and the fan motors. All of the original wiring downstream of the pink wires can be removed from the vehicle. The oem pink wires will connect to terminals #86 of the new relays.

quote:
Originally posted by PanteraDoug:
You indicate all new wires and I presume that is because you did this diagram for a new "SPST" fan replacement?...


The diagram is drawn for any installation involving higher power (amperage) motors than the oem motors. Which should fit the description for EVERY Pantera.

quote:
Originally posted by PanteraDoug:
...I need to be lead by the hand on this one...


No problem my friend, I'm honored to be able to help.

cowboy from hell


I hate to start removing the original wires if I can avoid it. No one will remember what went on and why, including me. At least someone will be able to figure it out by looking at the original diagram.

Can't I just leave them in place, add the relays, add the new power source cables?
What size fuses for the new 10 AWG wire should there be?
What amperage DIN relay should I look for?

What's the difference between + and -?
+ flows ^ and - flows v? (Just a little joke here)...well?
OK. Local Auto Parts has two that would seem to fit the bill.
Neither have the mounting tabs.

One is 50amp rating and a couple of the electrical tabs are twice the size of the one rated at 40 amps.

He doesn't have any of those universal mounting brackets for the relays. Does anyone have any suggestions about that.

Interestingly enough the 50 amp is $10 and 40 amp is $15?

OK Prof. Pence, which one do I need?
OK, got two 30 amp Dorman relays with the mounting tabs and some brown 10g wire. They had no pink. Can you believe that?
I sould be all set now. Smiler
quote:
Originally posted by PanteraDoug:
...I hate to start removing the original wires if I can avoid it. No one will remember what went on and why, including me. At least someone will be able to figure it out by looking at the original diagram.

Can't I just leave them in place, add the relays, add the new power source cables?
What size fuses for the new 10 AWG wire should there be?
What amperage DIN relay should I look for??


The oem wiring is insufficient in size. The higher current flow of the more powerful fan motors will result in a greater voltage drop through the wiring, leaving less voltage to operate the motors, the fans will not move air at their rated capacity. The wires operate hotter.

By the way, the 1/4" slip tab type terminals are available with gold plating, which will help eliminate some of the Pantera wiring gremlins. I buy mine at Osh.

quote:
Originally posted by PanteraDoug:
What's the difference between + and -? + flows ^ and - flows v?...


If she says "+", the night isn't over. If she says "-", you go home alone.

cowboy from hell
I know what you mean. If my wiring is of insufficient capacity she will say -.
I'll be left to my own devices of touching my + to any ground -.
It makes a very hot spark but really is a fatal attraction.
OK FOLKS, HERE'S THE GOOD'S
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RADIATOR-$488.39 NO TEMP SENSORS
DUAL PULLER FLEX FANS/FLX-220B-$225.88
wiringproducts.com
BOUSH 75 AMP POWER RELAY-$35.95
HIGH AMP CIRCUIT BREAKER WITH SWITCH-$26.95
pelicanparts.com
WAHLER THERMO FAN SWITCH 823-959-481F75-M5002
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panterasbywilkerson.com
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mcmastercarr
MOST HARDWARE.
FABRICATE THE REST

THIS TOOK AWHILE TO FIND AND WILL SAVE YOU SOME MONEY, IS ALL TOP QUALITY


THE SCHEMATIC IS TYPICAL TO MY 72 AND MAKES SENSE! I AM GOING TO RUN THE MERIAH'S AS BACKUP
AND USE THE FLEXLITE'S FOR PRIMARY'S/ALOT OF AIR FLOW!THE NEW PARTS, BREAKER/RELAY/FAN WILL RUN INDEPENDENT AND CONTINUE TO RUN AFTER THE CAR IS SHUT DOWN TO COOL WITH. THE BREAKER HAS A SWITCH ON IT IN THE EVENT THEY WON'T SHUT DOWN. IT WILL BE WIRED MORE OR LESS THE SAME AS THE PRINT GEORGE SUPPLIED.
MARK

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Last edited by sickcat
PRELIMINARY FITUP IN CAR IS TIGHT BUT DO-ABLE
PAINTING ALL PARTS WITH EASTWOODS CHASIS PAINT.
ITS EPOXY AND TOUGH, WON'T CHIP. PICTURE'S WILL FOLLOW.
IT'S GETTING BUTT COLD OUT HERE, TIME TO SHUT DOWN.

MARK
Continuing with set up, very tight.
made a line filter for the radiator,
will run this till the weather warms up.

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Last edited by sickcat
Mark,
Sorry I took so long! No problems at all on the hottest of days, in traffic stop & go or at 160+ across the desert for long runs, also I have the Edelbrock High flow water pump & brass thermostat.

Mark
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