# Heater Relay Dropout Issue



## EVDL List (Jul 27, 2007)

HI, Mark

I've set up my Echo the same way ( using the AC switch to control the 
heater) so I'm familiar with the wiring.

The fan takes a lot of current on high (about 12 amps) , so I can think of 
two possibilities:


1. Your 12V system voltage is dropping enough to drop the relay out. Put a 
voltmeter on your 12V system and watch the voltage as you change the fan 
speed.

2. There is enough voltage drop in the AC switch or wiring to allow the 
relay voltage to drop when the fan is on high.

To check this, put a voltmeter on the relay coil and watch as you change 
fan speeds.

What relay are you using?? It could be that the AC switch itself is the 
culprit - it's only designed to send a signal to the A/C amplifier, not 
power a large relay directly.

Mine is set up so that the AC switch only drives a small ( 17 ma coil) relay 
, and THAT relay drives the larger KUEP relay ( 100 ma coil). You could try 
something like that.



A third possibility ( this seems unlikely to me) is that the blower switch 
is faulty and is not grounding the heater relay ( which needs to be on to 
power the AC switch) when teh blower switch is in the "high" position. Or, 
if the ground wire from the heater switch were loose, it might have that 
same effect (because there is more current through that ground wire when the 
fan is on "high").


Phil




>From: Mark Dutko <[email protected]>
>Reply-To: [email protected]
>To: [email protected]
>Subject: Heater Relay Dropout Issue
>Date: Fri, 27 Jul 2007 06:49:38 -0700
>
>I have my heater relay for my 220V pack grounded on one 12v side and the 
>other going to the positive wire of my heater fan through a switch in the 
>dash which used to be the AC switch, When the AC switch is on and the fan 
>is turned on the relay makes contact on the first, second and third fan 
>speed position but on the fourth position or the highest, the relay drops 
>out and I need to turn the fan off to get it to contact again. I have a 
>diode across the relay coil (not sure if needed) and that's it. Any 
>suggestions as to a fix for this and why it happens on the high fan speed 
>setting?
>
>Thanks,
>
>Mark
>

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http://newlivehotmail.com


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## EVDL List (Jul 27, 2007)

On some models the high side of the switch is feed through a different source of power and not through the resistor block that feeds the lower fan speeds. It might be dropping out because of that?

Tom




> ---- Mark Dutko <[email protected]> wrote:
> > I have my heater relay for my 220V pack grounded on one 12v side and
> > the other going to the positive wire of my heater fan through a
> > switch in the dash which used to be the AC switch, When the AC switch
> ...


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## EVDL List (Jul 27, 2007)

I think the most likely would be the switch but if it could handle 
the draw from the relay it should continue to work as the relay draw 
should remain the same? The wire to the relay is spliced right at the 
motor and the AC switch has been completely isolated from the rest of 
the car electronics. My 12v system runs off two 55A DC/DC and a med 
sized aux battery. I will run some voltage tests later and see what 
happens. Perhaps when I tested it the pack was disconnected and it 
was on the aux battery only- I'll test again.



Thanks,

Mark





> Phil Marino wrote:
> 
> > HI, Mark
> >
> ...


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## EVDL List (Jul 27, 2007)

> Tom <[email protected]> wrote:
> 
> > On some models the high side of the switch is feed through a different
> > source of power and not through the resistor block that feeds the lower
> ...


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