TheSamba.com :: View topic - Hot Start Relay Diagram

Sun Jan 30, 2022 8:57 am

Can someone direct me to the hot start relay wiring diagram so I can DIY make one?

I've searched start relay and none of the posts I found had a schematic.

yes, its available form Uniwerks now as ThatBusGuy handed it off to them - and I want to make my own for DIY and because I may mount it near the steering column as a part of a kill switch rather than in the engine compartment https://www.uniwerksdesign.com/product/vanagon-hard-start-relay-kit/

Kill switch discussion - https://www.thesamba.com/vw/forum/viewtopic.php?p=9794803#9794803

Sun Jan 30, 2022 9:13 am

Ummm. If you don't know how relays work, read up on them. They couldn't be simpler. Installing one back aft is one of the simplest things to do. Since T3s need care and feeding, this is a good place to develop some new skills. Once you do that you will be able to design and build your own headlight relay system, then horn and some of the other stuff which should have had relays before they left the assembly line.

https://www.te.com/usa-en/products/relays-contactors-switches/relays.html

https://www.amazon.com/Pack-EPAuto-Relay-Harness-B...&psc=1

You can do it.

Duncan

Sun Jan 30, 2022 9:23 am

The purpose of the hot start relay is to drastically shorten the length of the wire that provides current to the starter solenoid. AFAIK you must install it in the rear near the starter for it to be effective. YMMV.

Sun Jan 30, 2022 9:29 am

RE: Duncan S -

Basically I don't want to re-invent the wheel if this is already documented somewhere.

I got relay operation knowledge....my questions was more general/specific....and I don't want to have the learning curve for the nuanced things of the Vanagon for this application - like the AUX batt relay gotcha and the automatic/Cruise gotchas..and having hints on which wires go from the ignition switch to the starter solenoid so I don't HAVE to figure out the Bentley wiring diagrams...I CAN do all that and I'm guessing someone else has already done this and its on here somewhere.

I'd rather spend more time on my removable steering wheel mod that I got inspired from your wooden steering wheel creation post.

Sun Jan 30, 2022 9:34 am

dobryan wrote: The purpose of the hot start relay is to drastically shorten the length of the wire that provides current to the starter solenoid. AFAIK you must install it in the rear near the starter for it to be effective. YMMV.

on BUSes yes, on Vanagon no

Different wiring per tencentlife (respect)
https://www.thesamba.com/vw/forum/viewtopic.php?p=2968114#2968114
https://www.thesamba.com/vw/forum/viewtopic.php?p=2969831#2969831

The Van tracker uses the relay as its kill switch https://www.thevantracker.com/product-page/stock

Sun Jan 30, 2022 9:56 am

vanis13 wrote:
The Van tracker uses the relay as its kill switch https://www.thevantracker.com/product-page/stock
The van tracker indeed kills the the ignition signal to the relay.

Maybe tell us what functionality you want. If it is a kill switch near the steering column that you need, then a hard start relay is not what you need.
Maybe you need both?

Sun Jan 30, 2022 10:27 am

I have the hot start relay in the engine bay where it is most effective.

But instead of grounding it there I ran the relay ground wire to a hidden switch in the front.

Sun Jan 30, 2022 10:57 am

VicVan wrote: vanis13 wrote:
The Van tracker uses the relay as its kill switch https://www.thevantracker.com/product-page/stock
The van tracker indeed kills the the ignition signal to the relay.

Maybe tell us what functionality you want. If it is a kill switch near the steering column that you need, then a hard start relay is not what you need.
Maybe you need both?

sure....wana interrupt the solenoid trigger signal to act as a starter kill switch. would like to do it near the dash. hints?

Sun Jan 30, 2022 11:07 am

You could use a self-latching relay up front feeding a hard-start relay by the solenoid. As in this diagram:

https://www.thesamba.com/vw/forum/viewtopic.php?p=9794889#9794889

Sun Jan 30, 2022 11:14 am

re: fxr

yes, its is what we covered in the kill switch topic - the general relay operation.

the question in this topic is - specifically about interrupting the solenoid signal - like which wire, where (preferably near steering column) is good to access, etc. related to the solenoid circuit.

Sun Jan 30, 2022 11:30 am

IMO, running a latching relay is superfluous if interrupting the starter circuit. It's necessary if interrupting the fuel pump or ignition which need to keep running after you let off the momentary switch, but that isn't the case with the starter circuit. There would be a very slight difference in behavior between the two, but the difference would be so slight it would probably not even be noticed by most people. With just the single relay and momentary switch, you would need to hold the momentary switch the entire time you cranked the engine. Letting up on the key or the momentary switch would cause the starter to stop cranking. With the added latching relay, you would only need to depress the momentary switch each time you wanted to crank the starter, but you could release the momentary switch once the starter was cranking, and the starter would keep cranking until you released the key back to run. If you stopped cranking with the key, then you would need to press the momentary switch again each time you wanted to crank again. IMO, that slight difference is not worth the added complication and additional irritating potential failure the added relay poses.

Sun Jan 30, 2022 11:59 am

re:waldo

I agree, the benefit of a relay on the starter circuit is that a very lightweight switch could be used - like someone suggested a Cruise control set button...something already there and discrete. I don't think a cruise button has enough capacity to activate the solenoid - and one doesn't want the starter engaging each time the cruise is set.

Sun Jan 30, 2022 12:00 pm

?Waldo? wrote: IMO, running a latching relay is superfluous if interrupting the starter circuit. It's necessary if interrupting the fuel pump or ignition which need to keep running after you let off the momentary switch, but that isn't the case with the starter circuit. There would be a very slight difference in behavior between the two, but the difference would be so slight it would probably not even be noticed by most people. With just the single relay and momentary switch, you would need to hold the momentary switch the entire time you cranked the engine. Letting up on the key or the momentary switch would cause the starter to stop cranking. With the added latching relay, you would only need to depress the momentary switch each time you wanted to crank the starter, but you could release the momentary switch once the starter was cranking, and the starter would keep cranking until you released the key back to run. If you stopped cranking with the key, then you would need to press the momentary switch again each time you wanted to crank again. IMO, that slight difference is not worth the added complication and additional irritating potential failure the added relay poses.
Not according to the diagram above. The self-latching relay is powered from the standard IGN (RUN) position, not the START position of the ignition key. It just enables the hard-start relay.

Sun Jan 30, 2022 12:18 pm

There is a fat red/black wire--6.0 or AWG 8 which goes from the ignition switch to the starter motor. Take that off, lengthen and attach it to terminal 86 of the relay. (white in the pic below.) The best location for the relay is in the middle of the half firewall high up so you can see it when you open the engine hatch. Run a new #6 wire from the starter motor to pin #30 of the relay. (Blue in the pic.) Run a new #8 wire from the starter motor, same place, to the alternator and then to pin# 87--yellow. Eliminate the original alternator wire as it is probably close to being shot anyway and if it fails, the car won't start.

Clean off the paint to bare metal and fasten the relay mount and pin 85 (black) to the ground/mounting screw. Done.

Duncan

Sun Jan 30, 2022 12:28 pm

fxr wrote: ?Waldo? wrote: IMO, running a latching relay is superfluous if interrupting the starter circuit. It's necessary if interrupting the fuel pump or ignition which need to keep running after you let off the momentary switch, but that isn't the case with the starter circuit. There would be a very slight difference in behavior between the two, but the difference would be so slight it would probably not even be noticed by most people. With just the single relay and momentary switch, you would need to hold the momentary switch the entire time you cranked the engine. Letting up on the key or the momentary switch would cause the starter to stop cranking. With the added latching relay, you would only need to depress the momentary switch each time you wanted to crank the starter, but you could release the momentary switch once the starter was cranking, and the starter would keep cranking until you released the key back to run. If you stopped cranking with the key, then you would need to press the momentary switch again each time you wanted to crank again. IMO, that slight difference is not worth the added complication and additional irritating potential failure the added relay poses.
Not according to the diagram above. The self-latching relay is powered from the standard IGN (RUN) position, not the START position of the ignition key. It just enables the hard-start relay.

So, elaborate on how the function differs from what I said. Be sure to consider that the stock ignition switch will not activate the start position a second time without moving the key back to OFF first.

Sun Jan 30, 2022 12:29 pm

vanis13 wrote: re:waldo

I agree, the benefit of a relay on the starter circuit is that a very lightweight switch could be used - like someone suggested a Cruise control set button...something already there and discrete. I don't think a cruise button has enough capacity to activate the solenoid - and one doesn't want the starter engaging each time the cruise is set.

You seem to have misinterpreted what I said. Keep the hot start relay if you want to remove the load from the ignition switch and eliminate the long power run for the solenoid. Interrupt the single hot start relay sense wire with the momentary switch. The second latching relay in the diagram that fxr posted is a superfluous overcomplication for no useful purpose.

Sun Jan 30, 2022 12:31 pm

Just run a discreet rocker type switch onto the fuel pump ground wire and job done

Sun Jan 30, 2022 12:33 pm

Luckyphil wrote: Just run a discreet rocker type switch onto the fuel pump ground wire and job done

That is perhaps easier but carries the significant downside that it doesn't automatically engage the theft deterrent. Instead, it requires the conscious act of setting the switch each time you leave the vehicle.

Sun Jan 30, 2022 1:10 pm

DuncanS wrote: There is a fat red/black wire--6.0 or AWG 8 which goes from the ignition switch to the starter motor.

Thanks helpful.

Was checking if this was already documented somewhere. Seems like (so far) not. Will work with above and Bentley to complete.

Sun Jan 30, 2022 1:27 pm

?Waldo? wrote: fxr wrote: ?Waldo? wrote: IMO, running a latching relay is superfluous if interrupting the starter circuit. It's necessary if interrupting the fuel pump or ignition which need to keep running after you let off the momentary switch, but that isn't the case with the starter circuit. There would be a very slight difference in behavior between the two, but the difference would be so slight it would probably not even be noticed by most people. With just the single relay and momentary switch, you would need to hold the momentary switch the entire time you cranked the engine. Letting up on the key or the momentary switch would cause the starter to stop cranking. With the added latching relay, you would only need to depress the momentary switch each time you wanted to crank the starter, but you could release the momentary switch once the starter was cranking, and the starter would keep cranking until you released the key back to run. If you stopped cranking with the key, then you would need to press the momentary switch again each time you wanted to crank again. IMO, that slight difference is not worth the added complication and additional irritating potential failure the added relay poses.
Not according to the diagram above. The self-latching relay is powered from the standard IGN (RUN) position, not the START position of the ignition key. It just enables the hard-start relay.

So, elaborate on how the function differs from what I said. Be sure to consider that the stock ignition switch will not activate the start position a second time without moving the key back to OFF first.
Ah yes, sorry! In which case the self-latching relay should be powered from the key-in position - which I would do anyway.