Hot Start Solenoid aka Heat Soak

[ob_wan]

Over the last few months, I've been having intermittent problems with the ability to start my car. it would typically click but I'd have to turn the key several times to get it to turn over, primarily when the car was hot. But it would even happen when cold.

A few weeks ago I met someone who was knowledgeable about vws and I had driven the vw on a fairly long trip. When I tried to restart the car, it originally clicked but then did nothing when turning the key over. I thought the battery was dead but it turned out the engine was hot and the wiring connections simply weren't sending enough voltage. I heard about the "hot start" relay but when I went to the auto parts store they wanted $60+ for the bosch kit(WR1?).

So, I went online and found the following:
http://www.wikihow.com/Install-Starter-Relay-for-H...%29-Beetle

bought the relay. bought the wire. already had the connectors. 10 mins of cutting/crimping wires. felt like 10 mins under the car with installation. No more clicks or duds when trying to turn the key. Probably common knowledge for those who have been driving vw's for a while but here's a cheap solution.
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1969 Fastback, 4-sp, carb'd

[Multi69s]

All wires have internal resistance. As the wires get older, this resistance increases to a point where you have a drop in voltage. Also, as a wire heats up, its internal resistance increases also. So you have a lose, lose situation. This is a good work around and even though many people have done it, your post is a good reminder for people who do not know about it.
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69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[ob_wan]

Thank you. I've done a lot of self-education over the last few years on resistance and old wiring and have experienced it on other vehicles so when this situation came up I wasn't surprised to see the same thing. Which was what caused the initial research. The odd thing that added to it was when the engine was hot, it no longer "clicked", but simply acted like the battery was dead. must have had the resistance in the wires + the resistance from a really hot bosch solenoid.

I'll point out one other recommendation given to me by someone who used to work for porsche/audi/vw at the dealership. one possible situation that can occur is that the starter brushes get so well worn, they actually get sharp edges on them which make it difficult for the starter to turn over. by champhering the edges of the starter bushings, you can bring new lift to the starter.

I learned about champhering by a vw mechanic years ago as applied to brakes. historically I had a terrible time with semi-metallic brake installs causing noise. tried the goo they recommend but no change. My friend recommended champhering the brake pads and I haven't had a single problem since. Made a lot of sense. Just another possible tip to your toolbox.
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1969 Fastback, 4-sp, carb'd

[KTPhil]

I doubt it is the wires themselves. The resistance increase is pretty minimal.

More likely it is the corroded and loose push-on connectors that caused the problem. This design is known to fail under vibration, age, and temperature cycling.

When such a hot start relay is installed those loose or corroded connections are jostled, tightened, or even replaced as part of the job. The relay is credited with fixing he problem, but it is more likely to be the new/rejuvenated connections that actually brought about the improvement.

It adds many more of the same failure-prone connectors to the circuit, which will eventually also fail. Better to replace and solder new connections. That would probably fix the problem.

The exception to my objectoon to relays is to deal with an old and rare ignition switch. Since the relay relieves the switch of the heavy solenoid current, the switch will last longer.

[ob_wan]

[Multi69s]

You are both right. The culprit is essentially corrosion. Some of it is internal to the wires and some of it is at the point of connection. The starter solenoid is magnetic and thus needs a specified voltage to engage. The path for the activation wire is fairly long. It picks up power from the fuse block, then goes through the ignition switch the goes through about 10' of wire. After 40 years, this whole path degrades and there is then a voltage drop at the solenoid and the solenoid can not engage properly. Yes you may be able to go through this entire path and clean up the connections and get it to work right. However, it is far easier to add a hot start relay (solenoid) and get it working quickly and cheaply.
_________________
69 road Bug 2110
73 Squareback - 2L, T4, Automatic W/ AC
Gone, but many fond memories 69 Baja Bug 2010 - 5 Rib Bus Transaxle
Gone but not forgotten 72 Baja Bug 2010
My builds
T4 into Squareback http://www.thesamba.com/vw/forum/viewtopic.php?t=458944&highlight=
Auto Trans Rebuild http://www.thesamba.com/vw/forum/viewtopic.php?t=516066&highlight=
AC in Squareback https://www.thesamba.com/vw/forum/viewtopic.php?t=...highlight=

[KTPhil]

A few more thoughts on these relays. I am sure there are special cases out there, and with 25 million of these cars around over the years, plenty of them.

But I've worked on the wiring of probably 25 old VWs over the years, and I have yet to find a problem I couldn't solve by replacing or reworking (soldering) the push-on connectors. I have not had to replace wires unless they burned from shorting (ignition is prone to this).

I have also removed the hard start relay off three cars after its additional connections also failed after a few years. Note these relays were added under the car. Putting it under the back seat away from water, salt, and vibration-mounting them might make them last longer.

I put a relay on a Euro '67 (6V) with the steering lock/ignition switch because they are so hard to find if they burn out. I also have seen them justofied on old Buses because the stock wire and length was marginal to begin with.

Try the simple and cheap first. If that fails, go to more serious measures like the relay.