dorman seat heater
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=138250
Printed Date: April 24, 2024 at 5:28 AM
Topic: dorman seat heater
Posted By: samhunter1
Subject: dorman seat heater
Date Posted: January 14, 2015 at 4:05 PM
have installed a Dorman seat heater in a Jeep Wrangler. The passenger’s side works as advertised. The driver’s side will work on high as it should, but on low which uses a relay in the circuit it will not disengage the relay when the switch is turned back to off. I am not sure how to post the relay diagram here, but you can search Dorman seat heater installation instructions to see the diagram. Any ideas on why the relay will not disengage? They are sending me a new harness, but I don’t know how long it will take.
Thanks,
Mark
Replies:
Posted By: shafferny
Date Posted: January 14, 2015 at 5:26 PM
Have you tried swapping the relay on the passengers side to the drivers side to see if the problem follows to the other side? You could try the same logic with the switch.
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Posted By: shark mobile
Date Posted: January 14, 2015 at 7:35 PM
Most seat heaters use Common five pin relays...Swapping out the relays though is a brilliant idea!
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Solder, tape, repeat!
Posted By: oldspark
Date Posted: January 14, 2015 at 8:04 PM
Agreed! (One of my initial test strategies is to rotate fuses & relays. Hence also my desire to only require a spare SPDT relay...)
Or course I'd probably use the switch's Hi to energrise the relay and carry the current for the Back heater (87 to GROUND; 86 to Hi; disconnect 87a), but if the currents are low - but then why the need for the relay? - just Ground the Common Back/Cushion junction and have Lo +12V power the Cushion on both Hi & Lo, and Hi +12V power the Back. Discard the G unless it's a illuminated switch. If it isn't the correct switch for that, why supply one with such a complicated or trouble-prone circuit?
Posted By: davep.
Date Posted: January 14, 2015 at 9:25 PM
oldspark wrote:
- but then why the need for the relay? - just Ground the Common Back/Cushion junction and have Lo +12V power the Cushion on both Hi & Lo, and Hi +12V power the Back. Discard the G unless it's a illuminated switch. If it isn't the correct switch for that, why supply one with such a complicated or trouble-prone circuit?
Look at that diagram again, OldDude. You missed how it works. Both elements are powered in both positions, not just one element for Lo. The relay puts the two elements in SERIES for "lo". The switch carries the full current for both heating positions.
The Ground on the switch must be for an indicator. The switch only switches power for both levels.
Again, the relay switches the elements from parallel (HIGH) to series (LOW). Pretty simple the way it is, IMO.
Posted By: davep.
Date Posted: January 14, 2015 at 9:32 PM
samhunter1 wrote:
it will not disengage the relay when the switch is turned back to off...... Any ideas on why the relay will not disengage?
The Power and HI terminals on the switch are reversed. Switch those two wires, and I bet it will work.
EDIT: It may not be these exact two wires, but it is probably a mis-connected pair of wires at either the relay or the switch. Compare the malfunctioning side to the 'good' side.
Does the switch have an indicator for each level? Ie, two bulbs? If so, another possibility is if the ground at the switch for the indicator is open. This would hold the relay on even after the switch was turned off.
Thanks for posting this. I learned a few things.
Posted By: oldspark
Date Posted: January 14, 2015 at 10:04 PM
davep. wrote:
The relay puts the two elements in SERIES for "lo".
With the two "negatives" hard bonded to GND? I think not - the centre link to GND would have to be broken and each other element end to +12V and GND respectively (as done for some head- or bright-lights as DRLs or parkers etc).
FYI - this is the diagram I am working off:
Posted By: davep.
Date Posted: January 14, 2015 at 10:13 PM
oldspark wrote:
davep. wrote:
The relay puts the two elements in SERIES for "lo".
With the two "negatives" hard bonded to GND?
But they are NOT "hard bonded to ground".
Look again. The two elements are common to each other, and to the "HI" terminal on the switch.
When in LO, the relay is energized, Power is available at 87, goes through the BACK through the common connection into the SEAT cushion and to ground. The two elements are in series in LO.
The HI terminal at the switch is N/C to anything in LO.
Posted By: davep.
Date Posted: January 14, 2015 at 10:23 PM
Here. See if this helps. Power flow in LO.
Power flow in HIGH:
Posted By: oldspark
Date Posted: January 14, 2015 at 10:31 PM
Ooops!!  My bad! Even if I did misread the series operation, htf could I miss the GND point - it is NOT their common!? 
And therefor my "preferred" wiring is crap - the normal relay-only power switching requires SPDT & SPST (DPDT) contacts. For headlights etc yes, but not low current applications where a suitable switch is available.
Sorry for that.
I'll bug out - I agree with davep's incorrect wiring reply.
Posted By: davep.
Date Posted: January 14, 2015 at 10:35 PM
It's all good. I learned some stuff. Which is why I participate here. If others do too, even better. I'm out too. Cheers.
Posted By: samhunter1
Date Posted: January 15, 2015 at 4:18 PM
Sorry guys, It has been a busy day.
I have tried switching the good side relay and switch over to the bad side, and nothing changed. The bad side was still bad and the good side was still good. I need to look at the wiring on the good side and compare it to the bad side. I agree that it is a strong possibility that it is wrong.
Thanks for all of the help with this issue.
Mark
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