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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Thu Sep 20, 2018 7:17 am Post subject: Repurposing your rear defrost relay as a hard start relay |
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I have been contacted by a couple of other samba members recently asking if I could post instructions on how to use a rear defrost relay as a hard start relay. If you have a rear defrost system with a shot grid (like mine) and are having intermittent problems with the starter not turning over when you turn the key, there is a good chance this can solve your problem.
Under the rear seat driver's side you will see your rear defrost relay mounted to the chassis, you will also see the red (or red/black) starter wire coming from the ignition switch up front, passing through a clear plastic connector then it should go into a sheathing that exits the floor pan through a hole and goes to the starter.
1. Disconnect the red (or red/ black) wires from either side of the plastic connector.
2. Connect the wire lead coming in from the ignition switch to terminal 85 on the rear defrost relay.
3. Connect the wire lead going out to the starter to terminal 87 on the rear defrost relay.
4. Connect a lead from the B+ terminal on the voltage regulator to terminal 30 on the rear defrost relay-- in fact if you haven't messed with the rear defrost relay wiring you should already have this lead with an 8 amp inline fuse. I had removed that wire some time back so I ran a new one.
(The rear defrost relay grounds through its metal housing mounted to the chassis of the car so you should not have to run an extra ground lead.)
Here is a picture of my setup with the wires marked- note I used jumper wires and wire nuts to extend the wire lengths so they would reach the defrost relay:
Those two red wires were the ones originally connected through the plastic connector, I simply removed them from the connector and jumpered each to the appropriate terminal on the relay. (BTW ignore that blue wire going through another plastic connector, that is my autostick ATF warning light lead, most of you will not have that wire.)
Hope this helps _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor
Last edited by sb001 on Thu Sep 20, 2018 8:00 am; edited 2 times in total |
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Thu Sep 20, 2018 7:23 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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P.S. In case you are wondering which terminals are which on the rear defrost relay, they should be stamped on the outer housing of the relay next to each terminal, but they can be REALLY hard to see so you might have to clean some crud off the top of the relay and shine a light in there to see them. If you have a relay similar to mine in the picture above then the terminals should be the same, but I believe later models used a different relay box so the terminals might be different on those.
Please double check your relay and make sure you have identified the correct terminals to wire this up before proceeding! _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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Cusser Samba Member
Joined: October 02, 2006 Posts: 31268 Location: Hot Arizona
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Thu Sep 20, 2018 8:05 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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One more thing I will hasten to add-
I am not too familiar with the different model rear defrost relay boxes, but there may be some that used a plastic housing and thus NOT ground through the metal housing like mine does. If not, then look to see if there is a brown wire lead coming off the relay (should be coming from terminal 86 on the relay) to a ground point somewhere, this will be your ground lead. If not then look for terminal 86 on the relay and run a ground wire to a good ground point. _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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TheDharma Samba Member
Joined: September 13, 2018 Posts: 18 Location: Rochester, NY
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Posted: Thu Sep 20, 2018 8:36 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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Thanks for the write up! Ill try fiddling with it tonight when I get back! |
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HippyTom Samba Member
Joined: December 18, 2013 Posts: 676 Location: Florida, West Pasco
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Posted: Thu Sep 20, 2018 9:14 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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I might re-wire my rear defrost switch as a secret cutoff that had to be turned on before the car will start. The switch and defrost work, but don’t really need it in FL. _________________ 51 Standard Split Window Bug
57 Oval Bug, 80s Custom Car
62 Sunroof Bug, Psychedelic Hippy Car
63 Sunroof Bug, Former Herbie, Dad bought in 66
79 Super Beetle Convertible, OG paint and interior
69 Weekender Bus
77 Bay Window Bus, OG paint
69 Bug Convertible - SOLD
71 Super Beetle Vert - SOLD
64 Karmann-Ghia, barn find - SOLD |
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joey1320 Samba Member
Joined: September 12, 2006 Posts: 2325 Location: Cleveland, OH
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Thu Sep 20, 2018 2:22 pm Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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HippyTom wrote: |
I might re-wire my rear defrost switch as a secret cutoff that had to be turned on before the car will start. The switch and defrost work, but don’t really need it in FL. |
Your defrost grid actually works??? _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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HippyTom Samba Member
Joined: December 18, 2013 Posts: 676 Location: Florida, West Pasco
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Posted: Thu Sep 20, 2018 7:49 pm Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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sb001 wrote: |
HippyTom wrote: |
I might re-wire my rear defrost switch as a secret cutoff that had to be turned on before the car will start. The switch and defrost work, but don’t really need it in FL. |
Your defrost grid actually works??? |
Parts of it do...it's not great, but...that switch would make a great hidden starter shut off. It would cause enough frustration to deter the typical crackhead or teenager that has to put forth any effort to figure it out. _________________ 51 Standard Split Window Bug
57 Oval Bug, 80s Custom Car
62 Sunroof Bug, Psychedelic Hippy Car
63 Sunroof Bug, Former Herbie, Dad bought in 66
79 Super Beetle Convertible, OG paint and interior
69 Weekender Bus
77 Bay Window Bus, OG paint
69 Bug Convertible - SOLD
71 Super Beetle Vert - SOLD
64 Karmann-Ghia, barn find - SOLD |
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kangaboy Samba Member
Joined: August 28, 2010 Posts: 1062 Location: St. Louis, Mo
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Posted: Fri Sep 21, 2018 7:11 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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sb001 wrote: |
HippyTom wrote: |
I might re-wire my rear defrost switch as a secret cutoff that had to be turned on before the car will start. The switch and defrost work, but don’t really need it in FL. |
Your defrost grid actually works??? |
Was gonna ask how much it might cost to get new rear glass with the grid in it...first link I could find suggests that I will not be having a rear defrost in the near future
https://www.mtmfg.com/part/view/rear-window-glassw...gK0S_D_BwE _________________ -74 Standard - "CaliBug" 2084T, MS3X w/FI and Crank Fire
-76 Westy - "Gandalf"
-18 GTI SE
skills@eurocarsplus wrote: |
that fucking thing looks like it drove through a J.C. Whitney catalogue and hit everything on the way out |
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Cusser Samba Member
Joined: October 02, 2006 Posts: 31268 Location: Hot Arizona
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Posted: Fri Sep 21, 2018 9:09 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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I got my 1970 when it was just 2 years old. I remember that the electric defrost did not work very well, especially on short trips. Luckily, we rarely had frost so rear window rarely needed that, in Arizona. I'm pretty sure that my 1970's rear window has infinite resistance/open these days.
But it's way past being my daily driver !!! I just won't drive it under such conditions. _________________ 1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297 |
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Fri Sep 21, 2018 9:34 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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kangaboy wrote: |
sb001 wrote: |
HippyTom wrote: |
I might re-wire my rear defrost switch as a secret cutoff that had to be turned on before the car will start. The switch and defrost work, but don’t really need it in FL. |
Your defrost grid actually works??? |
Was gonna ask how much it might cost to get new rear glass with the grid in it...first link I could find suggests that I will not be having a rear defrost in the near future
https://www.mtmfg.com/part/view/rear-window-glassw...gK0S_D_BwE |
For some unfathomable reason their clear glass (no defrost) is even more expensive!
https://www.mtmfg.com/part/view/rear-window-glass-...1-845-501M
If you already have the clear glass just get a Frost Fighter kit:
https://www.frostfighter.com/clear-view-defrosters-09.htm
Here's a thread where a fellow Samba member bought one to show how well it works:
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
Be glad you don't have a 65-71, clear rear glass is apparently impossible to source new for those! If I ever have to purchase new rear glass for my 69 I have no choice but to pay for one with a defrost grid. _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Fri Sep 21, 2018 9:39 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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Cusser wrote: |
I got my 1970 when it was just 2 years old. I remember that the electric defrost did not work very well, especially on short trips. Luckily, we rarely had frost so rear window rarely needed that, in Arizona. I'm pretty sure that my 1970's rear window has infinite resistance/open these days.
But it's way past being my daily driver !!! I just won't drive it under such conditions. |
I posted here years back asking about how you test a rear defrost grid i.e. what is the proper level of resistance you are supposed to get on your meter with a working grid, absolutely no one could answer that question. I guess you find out anyway when you try to use it! Like the dash brake warning light _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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Lingwendil Samba Member
Joined: February 25, 2009 Posts: 3987 Location: Antioch, California, a block from the hood
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Posted: Fri Sep 21, 2018 9:56 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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Wire nuts?!
Come on, man. Just strip and terminate another wire, it's not that hard.
Or, simply fix the existing wiring and do without
(here I go, better duck behind a table before the wrath of thesamba gets me!)
I've never seen the need for a hard-start relay in a 12 volt car that had it's wiring in good condition, but for whatever reason its a common "fix" on these cars when simply replacing wire terminals and/or cleaning terminals will suffice. Smear some dielectric grease on the contacts to keep corrosion away.
(I'm not trying to be or sound hostile, I understand this may be a good fix for some, and I sure do enjoy the salty replies SB tends to get, so, carry on ) _________________ 73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!
Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884
Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087! |
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Fri Sep 21, 2018 10:07 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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Lingwendil wrote: |
Wire nuts?!
Come on, man. Just strip and terminate another wire, it's not that hard.
Or, simply fix the existing wiring and do without
(here I go, better duck behind a table before the wrath of thesamba gets me!)
I've never seen the need for a hard-start relay in a 12 volt car that had it's wiring in good condition, but for whatever reason its a common "fix" on these cars when simply replacing wire terminals and/or cleaning terminals will suffice. Smear some dielectric grease on the contacts to keep corrosion away.
(I'm not trying to be or sound hostile, I understand this may be a good fix for some, and I sure do enjoy the salty replies SB tends to get, so, carry on ) |
That's fine I understand the concern about using wire nuts, that was supposed to be temporary until I got a set of splicers but never got around to it yet. The wire nuts are working fine so it kind of slipped my mind.
If you think that's bad, check out what I did with my D+ generator wire!
It's actually been like that going on 2 years now with no issues.
Meh _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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Lingwendil Samba Member
Joined: February 25, 2009 Posts: 3987 Location: Antioch, California, a block from the hood
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Fri Sep 21, 2018 10:15 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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AS far as "fixing" the existing wiring vs using a HSR, the HSR is a much more viable long-term option. You can clean up the connections on the existing wiring all you want but the problem will likely come back. A HSR saves the existing wiring from further degradation and is so cheap why not just use it. _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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sb001 Samba Member
Joined: May 19, 2011 Posts: 10399 Location: NW Arkansas
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Posted: Fri Sep 21, 2018 10:16 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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Lingwendil wrote: |
You're a madman |
I'll get around to "making it right" one of these days.
Moral of this thread; do as I say not as I do!!! _________________ I'm the humblest guy on this board.
1969 autostick sedan, family owned since new
1600 SP engine
Solex 30 PICT 3 carburetor
Bosch 113905205AE autostick distributor |
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Tim Donahoe Samba Member
Joined: December 08, 2012 Posts: 11739 Location: Redding, CA
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Posted: Fri Sep 21, 2018 10:23 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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Kangaboy’s M&T Manufacturing’s photo shows a window with a grid. The grid doesn’t appear to be like any stock one I’ve ever seen. In fact, it looks exactly like a Frostfighter grid has been added. If you inspect where the grids make contact with the vertical bars, this should be evident.
I have to wonder why a window with a grid added is cheaper than one without it. Also, the number of grids in the photo are twice the amount in the OEM windows. Wouldn’t they pull more amps than the stock 8 amp fused system can deliver?
Tim _________________ Let's do the Time Warp again!
Richard O'Brien |
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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Fri Sep 21, 2018 10:46 am Post subject: Re: Repurposing your rear defrost relay as a hard start relay |
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So I can only drive with the defroster on? what turns on the defrosyer any way? my car must be frost free as it only has flasher&light switch..and of coarse the radio and ignition switch. but hopefully some day it will have a ac switch!!! I guess Im good to go since mine is apparently frost free. but none the less thanks to the op for showing how to repourpose those parts for those whoo have them.
it also helps if you run a #10-12 wire from the alt out put to the battery/or starter directly( for those whoo have the internal regulated alt. that takes the charging load off the main harness and those connectors that tend to melt under the rear seat. mine runs to the starter positive lug with the + batter cable on it.
many people snatch parts off and throw them away when they think they dont need them...there are many parts that can be re purposed...hell my steering wheel adapter was a forged ford 351 piston in a former life. and my cylinder heads were once beer cans!!!! well they could of been...and might bee. |
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