daveturnbull

PTC heater wiring

24 posts in this topic

So as many of you have already done, I plan to graft a nice electric heater element from a modern car into my defender heater box. After a bit of research on sizes of them, I've plumped for one from a Honda civic.

Now to my question, how to wire it in. There are 7 wires to choose from. I'm guessing that the 3 coloured pairs, one of each with a trace are the live / earth for each element, but what is the 7th black wire for?

rsz_dsc_1711.jpg

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A post I found on a civic forum seems to suggest that 4 of the wires are grounded. (Not sure though, I haven't registered so cant see the pics)

It wouldn't be too surprising, these things draw a lot of current so more ground wires is always good.

I wonder if it might be used by an ECU to check how much current the heater is drawing, using the ground wiring as a simple current shunt. I'd probably think of doing that if I were designing it from scratch. If it's that, you can safely ignore it. (It will be commoned with one of the heater ground wires if so.)

If you've got a meter than can measure low ohms, it should be pretty easy to figure whats what.


 

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Is your multiplug numbered? I found the above post too...very interesting stuff. It would appear 4,5,6 & 7 are your grounds, 1,2&3 being the live feeds. Each element gets a 40a relay with so its drawing a fair bit of current....I was slightly concerned at the Honda guy only using 1mm2 for this! Looking at the above pic would appear to be 4mm2?

Should be quite a hefty heat output, 1.44kw if drawing 120a at 12v. Following this with interest :) 

 

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No pin numbers in the multi plug, bit they are arranged in 2 rows. The top row being the 3 solid colours, and the bottom row the colours with trace and the Black.

So top row to live, bottom to earth.

DSC_1712-1024x576.JPG

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So are you planning to remove the matrix and insert this in lieu or as an extra layer of heat input? The latter would appear to be the way it's utilised in the Honda until the diesel is at temp. 

On my google searching I found that this is widely used on electric vehicles in combination with a heat pump arrangement (air con in reverse) as you obviously have no engine for a water matrix.

I've got a spare heater assembly so might add this to the list of upgrades ;)

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I'll be adding it as an extra layer for initial heat until the stock matrix warms up, much like TSD has done in another thread. I'll try and find the link for you when I'm back on a proper PC. 

I've got some small 12v fans out of an old server in the garage. Considering strapping them to one side to help with air flow too. Some bench testing needed first I think. 

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I've got one of those Landreizeger heater controllers to install to allow some more variation of the fan speed, the 200tdi isn't the slowest at producing heat but some extra quick warmth wouldn't go amiss.

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When "adding it as an extra layer for initial heat ...", I would add it downstream of the original matrix so that warmed air doesn't flow over the heatsink of a cold matrix.

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1 hour ago, DaveSIIA said:

When "adding it as an extra layer for initial heat ...", I would add it downstream of the original matrix so that warmed air doesn't flow over the heatsink of a cold matrix.

That's exactly the plan. It had the added benefit that once the water matrix heats up and warm air is passing over the PTC the amps it is sucking up should drop significantly. 

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I pretty much copied what TSD did re positioning.

My electric heater element seems to have died, or at least it no longer produces any discernible heat.

However having replaced my thermostat a little while ago I'm finding the V8 now warms up pretty quickly. Now the cabin of the 110 reaches toasty temps in less than the 10 minutes it takes to get to work. I've consequently found little incentive to take the heater out to see WWW.

 

I have obtained a blower fan and motor from a D1 that looks like it might graft to the Defender heater box. Initial tests show it might make a good hovercraft :) 

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My bet would be it's taken out the fuse or more likely the relay(s) you used. These things are great for sorting truth from bsht in manufacturers ratings :rolleyes:

Must admit I haven't used mine in a while since I don't drive the bex everyday.

I've got a blower that miketomcat gave me some time back, plastic fan in a plastic snail housing that produces a fair gale. Think it was from a Suzuki IIRC, mike might remember.

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If it was off a suzuki then it would be from an early swift as the only cars I've broken are minis, land rovers and a swift.

Mike

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That's my next plan - to try and find a Blower fan with a bit more oomph. I've been looking at old car ones, with a simple 2 pin plug, none of that fancy shizzle with built in speed control and sensors. The trouble is without having a selection in front of you it's hard to work out what might fit well in the LR housing. 

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RRC and Discovery heaters are very powerful and easy to come by, so if there is a way of grafting the guts of one into the housing from a Defender, or a custom housing that takes the same space, then it should do well.  Another option would be to fit the RR unit in parallel to the Defender unit (so that the Defender unit can still demist the screen) under the seat base or tub floor with hoses to outlets wherever needed.

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23 hours ago, TSD said:

My bet would be it's taken out the fuse or more likely the relay(s) you used. These things are great for sorting truth from bsht in manufacturers ratings :rolleyes:

 

Well the relay is allegedly rated at 140A, and the fuse at 120A. The relay still switches 12V measured with a multimeter. That's what made me wonder if the PTC had died. Do I recall reading somewhere that they're self regulating?

4 hours ago, Snagger said:

RRC and Discovery heaters are very powerful and easy to come by, so if there is a way of grafting the guts of one into the housing from a Defender, or a custom housing that takes the same space, then it should do well.  Another option would be to fit the RR unit in parallel to the Defender unit (so that the Defender unit can still demist the screen) under the seat base or tub floor with hoses to outlets wherever needed.

The snail shell shaped housing looks surprisingly similar to a Defender one. Will see if I can take a photo later.

Without removed the wing though it's hard to tell whether it will actually fit, and I don't have a spare Defender heater box to offer it up to to either.

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Just found this thread on a US forum about defender blower motor upgrades. Ultimately it suggests using a VDO PM137 which typically are available cheaply in the states but not over this side of the pond.

Another poster also mentioned the dimensions of the stock squirrel cage are 5 3/8" diameter by 2 1/2" depth so that gives some scope for comparison of various car options.

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Dave, I get the impression from those threads that the motor is a series upgrade rather than 90/110 ?

Mo

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Mo, it was This thread that led me onto the one I linked above. Here the guy is refurbishing a defender heater box and uses a PM136 motor, which is the 1 wire version of the PM137 with an internal ground. 

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Ah I see.

It does seem to promise far better performance than what we have now.

I'm using a bilge blower at the moment which while it does improve the air flow still isn't quite there. 

Mo

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So after much perusing of pictures and pestering of various eBay sellers to measure things for me, only a small percentage of which actually gave a meaningful reply, I took a punt on a couple of cheap blower fans from various cars that looked about right.

The first one turned up yesterday. It's a Denso 162500-5570 and it squeezes perfectly into the defender snail housing. Obviously bolting it in will need a little adjustment - take the old studs out, drill some new holes and fit rivnuts, but I'm chuffed with how well it fits.

As it's a fairly old school design, with nuts and screws holding it together, I decided it needed to be taken apart and the bronze bearings sprayed with a little silicone lube. Tested on the bench with a spare battery it spins up a treat and blew a fair gale. :D

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FYI I had a quick google of that Denso number, and  as well as fitting a Suzuki, it also registered a hit as a Discovery 2 blower motor.

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I found that too, but none of the Disco 2 blower motors I could find looked anything like it, so might be an error. (Yes, the internet is occasionally wrong)

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Another one I'm 99% sure is exactly the same motor is a Rover 200 / 400 Mk2 (wedge shape). It has a different plastic cover on the back for the air recirc to cool the motor but other than that looks identical, and measurements seem to match up too.

s-l500 (1).jpgs-l500.jpg

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Made by Hella? Looks identical, again apart from the back portion, to my Audi's one.

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