Re: 1986 toyota celica heating problems

In article <d358e$45e52ce7$47c2b532$391@msgid.meganewsservers.com>
rokigawaATtristarassociatesDOTcom "Ray O" writes:
[color=blue]
> [...] I doubt if you can buy a resistor pack at an auto parts
> store, but if you know how to solder, you can purchase the
> individual resistors at an electronics store and replace them.
> You have to look at the resistance of each resistor to find an
> acceptable substitute.[/color]

Make sure the resistors are constructed so as to handle whatever
power you are asking them to dissipate. The tiny resistors that
one finds used in low-power electronics, for example, tend to be
good for only 1/10 to 1/4 watt (or used to be, back when I did a
lot of that stuff). Resistors for "power" jobs should show very
clearly what their rating is, fortunately.

Now to calculate the power handling. If the resistors are being
wired "in parallel" (wire at one end tied to corresponding wires
of all other resistors, with the same at the other end) then you
should be safe in allowing for dropping the full battery voltage
across the resistors; of course, in practice the fan will handle
some of it. The watts dissipated by a resistor of R ohms when V
volts are dropped across it are V * V / R. Do this sum for each
resistor and it will give you the individual wattage ratings.

If the resistors are wired "in series", it gets more complicated
than I think should be rushed through here. Parallel seems more
likely to serve your needs.

BTW, large power resistors are often made to be bolted to a heat
sink. It then becomes more of a construction project. Overall,
it is probably best to try doing it as in the existing setup.

Ray can probably set yea/nay on this: maybe the shop manual says
what the resistor wattage should be.
--
Andrew Stephenson

"Andrew Stephenson" <ames@deltrak.demon.co.uk> wrote in message
news:1172669666snz@deltrak.demon.co.uk...[color=blue]
> In article <d358e$45e52ce7$47c2b532$391@msgid.meganewsservers.com>
> rokigawaATtristarassociatesDOTcom "Ray O" writes:
>[color=green]
>> [...] I doubt if you can buy a resistor pack at an auto parts
>> store, but if you know how to solder, you can purchase the
>> individual resistors at an electronics store and replace them.
>> You have to look at the resistance of each resistor to find an
>> acceptable substitute.[/color]
>
> Make sure the resistors are constructed so as to handle whatever
> power you are asking them to dissipate. The tiny resistors that
> one finds used in low-power electronics, for example, tend to be
> good for only 1/10 to 1/4 watt (or used to be, back when I did a
> lot of that stuff). Resistors for "power" jobs should show very
> clearly what their rating is, fortunately.
>
> Now to calculate the power handling. If the resistors are being
> wired "in parallel" (wire at one end tied to corresponding wires
> of all other resistors, with the same at the other end) then you
> should be safe in allowing for dropping the full battery voltage
> across the resistors; of course, in practice the fan will handle
> some of it. The watts dissipated by a resistor of R ohms when V
> volts are dropped across it are V * V / R. Do this sum for each
> resistor and it will give you the individual wattage ratings.
>
> If the resistors are wired "in series", it gets more complicated
> than I think should be rushed through here. Parallel seems more
> likely to serve your needs.
>
> BTW, large power resistors are often made to be bolted to a heat
> sink. It then becomes more of a construction project. Overall,
> it is probably best to try doing it as in the existing setup.
>
> Ray can probably set yea/nay on this: maybe the shop manual says
> what the resistor wattage should be.
> --
> Andrew Stephenson
>[/color]

Very good points! I was thinking more in terms of removing the bad
resistors, taking them to an electrical supply store, asking them for
suitable replacements, and re-soldering the replacements in the same
location. Hopefully, the electrical supply store would know which
replacements work.
--

Ray O
(correct punctuation to reply)