Optional Starter Relay, Add a relay to protect the ignition switch |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Optional Starter Relay, Add a relay to protect the ignition switch |
Artfrombama |
Feb 23 2024, 03:01 PM
Post
#1
|
Member Group: Members Posts: 51 Joined: 21-January 24 From: Alabama Member No.: 27,870 Region Association: South East States |
On a previous 914 I had many years ago I experienced a "no crank" condition that I traced back to my ignition switch. It seems that in the start circuit on the switch, when the key is released a tiny "backfeed" of current from the starter solenoid arcs across the terminals on the ignition switch, and over time damages the contacts.
After a little research I determined there are two ways to stop this "current backfeed", one is to install a diode to ground in the starter wire, another (which I did) was to install a simple 5 pin relay. Hope this is of some help, please disregard or delete if this has been discussed before. |
GregAmy |
Feb 23 2024, 03:09 PM
Post
#2
|
Advanced Member Group: Members Posts: 2,311 Joined: 22-February 13 From: Middletown CT Member No.: 15,565 Region Association: North East States |
|
Artfrombama |
Feb 23 2024, 03:13 PM
Post
#3
|
Member Group: Members Posts: 51 Joined: 21-January 24 From: Alabama Member No.: 27,870 Region Association: South East States |
Whoosh, right over my head (IMG:style_emoticons/default/rolleyes.gif) |
GregAmy |
Feb 23 2024, 03:50 PM
Post
#4
|
Advanced Member Group: Members Posts: 2,311 Joined: 22-February 13 From: Middletown CT Member No.: 15,565 Region Association: North East States |
A guy goes to prison for the first time, gets walked into his cell in the middle of a long cellblock. The cellblock is mostly quiet, not much going on.
The silence is suddenly broken when someone in the cellblock yells, "58!" and the place breaks out in laughter. Then it's quiet again. A few minutes later someone yells out "143!" and the place laughs again. Then more silence. A few minutes after that someone yells "24!" and the place roars in laughter and someone says "Yup, that's a good one". Then more silence. The new guy taps on the wall and whispers to the guy next to him, "hey, what's what all about, calling out numbers?" Guy next door says, "oh, we've all been here so long that we numbered the jokes, and we just call out the number when we want to tell the joke." "OK", the guy thinks to himself. "I'll give it a shot" and he yells out "75!" Silence. New guy taps on the wall and says, "hey, what happened? Why is no one laughing?" Guy next door replies, "you didn't tell the joke right." |
ClayPerrine |
Feb 23 2024, 04:11 PM
Post
#5
|
Life's been good to me so far..... Group: Admin Posts: 15,503 Joined: 11-September 03 From: Hurst, TX. Member No.: 1,143 Region Association: NineFourteenerVille |
It's not you. The topic of adding that relay to the starter circuit has been an ongoing point of contention for years on this forum. Some say it is necessary. Some say it is not. Some say put in a Ford starter relay. Some say to use a gear drive starter. So go back and read some of the links in that search you were sent. And welcome to 914World. (IMG:style_emoticons/default/welcome.png) |
914Mike |
Feb 23 2024, 04:23 PM
Post
#6
|
Member Group: Members Posts: 330 Joined: 27-January 03 From: San Jose, CA Member No.: 198 |
... The topic of adding that relay to the starter circuit has been an ongoing point of contention for years on this forum. Some say it is necessary. Some say it is not. Some say put in a Ford starter relay. Some say to use a gear drive starter. So go back and read some of the links in that search you were sent. And welcome to 914World. (IMG:style_emoticons/default/welcome.png) And yet no modern car is without a relay and most have a diode or similar as well, which protects the relay contacts. Even the relay coil gets a diode to minimize the wear on the key switch. Common practice that began in the electronics industry and then moved to the automotive. |
emerygt350 |
Feb 23 2024, 08:07 PM
Post
#7
|
Advanced Member Group: Members Posts: 2,132 Joined: 20-July 21 From: Upstate, NY Member No.: 25,740 Region Association: North East States |
Takes ten minutes to put in the ford solenoid with zero damage to your car and costs 20 bucks or less. Don't let the other inmates scare you.
|
bdstone914 |
Feb 23 2024, 09:32 PM
Post
#8
|
bdstone914 Group: Members Posts: 4,533 Joined: 8-November 03 From: Riverside CA Member No.: 1,319 |
I sold a rebuilt starter to a guy about a year ago. He calked saying he thought the starter was now gone bad. Turns out the Ford solinoid he added had gone bad and only outputting 7 volts.
|
Artfrombama |
Feb 23 2024, 10:46 PM
Post
#9
|
Member Group: Members Posts: 51 Joined: 21-January 24 From: Alabama Member No.: 27,870 Region Association: South East States |
Someone tell me why the Ford solenoid (relay) is superior than the smaller Bosch 5 pin relay
|
Superhawk996 |
Feb 24 2024, 12:40 AM
Post
#10
|
914 Guru Group: Members Posts: 5,878 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
42 (IMG:style_emoticons/default/stirthepot.gif)
Typical Bosch aftermarket automotive relay is rated 30A. The generic Ford starter relay is rated for 150A or a little more depending on who’s making and rating them. Starter solenoid draws around 25A nominal at 75F ambient temp. That’s not a lot of margin in the Bosch relay. The standard Bosch 30A automotive relay doesn’t have an integrated flyback (freewheeling) diode. Bosch requires that diode on an inductive load (i.e. solenoid) in order to achieve their rated life cycle for the relay. As mentioned previously the lack of a flyback diode will lead to burned relay contacts that eventually malfunction. Note: the Ford solenoid doesn’t have an integrated diode either which is why those can malfunction too despite the much higher current rating. I measured the starter solenoid current draw a while back using a 50A, 75mV shunt resistor. This was on a properly operating starter. My bet is that solenoid draw is even higher in cold weather. I’d also bet there are a statistical population of solenoids out there that draw more current than my random sample of one. (IMG:style_emoticons/default/welcome.png) |
Superhawk996 |
Feb 24 2024, 01:42 AM
Post
#11
|
914 Guru Group: Members Posts: 5,878 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
I sold a rebuilt starter to a guy about a year ago. He calked saying he thought the starter was now gone bad. Turns out the Ford solinoid he added had gone bad and only outputting 7 volts. I have yet to see anyone install a proper flyback diode in parallel with the solenoid load on either a Ford or a Bosch solenoid install. Flyback voltage can be very high (hundreds to thousands of volts). Even though it only occurs for milliseconds, the arching can eventually burn contacts regardless of the Bosch or Ford steady state current rating. |
StarBear |
Feb 24 2024, 08:36 AM
Post
#12
|
Senior Member Group: Members Posts: 1,906 Joined: 2-September 09 From: NJ Member No.: 10,753 Region Association: North East States |
Takes ten minutes to put in the ford solenoid with zero damage to your car and costs 20 bucks or less. Don't let the other inmates scare you. (IMG:style_emoticons/default/agree.gif) Easy. Cheap. Fast. Perfect 914 solution. Not one problem since doing it. Instructions from a Mark Henry thread. (Haven’t seen him posting for quite a while. Deceased?) |
Artfrombama |
Feb 24 2024, 10:56 AM
Post
#13
|
Member Group: Members Posts: 51 Joined: 21-January 24 From: Alabama Member No.: 27,870 Region Association: South East States |
42 (IMG:style_emoticons/default/stirthepot.gif) Typical Bosch aftermarket automotive relay is rated 30A. The generic Ford starter relay is rated for 150A or a little more depending on who’s making and rating them. Starter solenoid draws around 25A nominal at 75F ambient temp. That’s not a lot of margin in the Bosch relay. The standard Bosch 30A automotive relay doesn’t have an integrated flyback (freewheeling) diode. Bosch requires that diode on an inductive load (i.e. solenoid) in order to achieve their rated life cycle for the relay. As mentioned previously the lack of a flyback diode will lead to burned relay contacts that eventually malfunction. Note: the Ford solenoid doesn’t have an integrated diode either which is why those can malfunction too despite the much higher current rating. I measured the starter solenoid current draw a while back using a 50A, 75mV shunt resistor. This was on a properly operating starter. My bet is that solenoid draw is even higher in cold weather. I’d also bet there are a statistical population of solenoids out there that draw more current than my random sample of one. (IMG:style_emoticons/default/welcome.png) I didn’t think the 914 relay would draw that much current, so you’re saying the Bosch 5pin relay was really “right on the edge” as far as having the capacity to actuate the starter coil. I have a couple of non-Bosch 5 pin relays that are rated 40 amp and have seen some for sale rated 50 amp. |
dr914@autoatlanta.com |
Feb 24 2024, 11:20 AM
Post
#14
|
914 Guru Group: Members Posts: 7,887 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
|
StratPlayer |
Feb 24 2024, 11:28 AM
Post
#15
|
StratPlayer Group: Members Posts: 3,278 Joined: 27-December 02 From: SLC, Utah Member No.: 27 Region Association: Rocky Mountains |
|
Front yard mechanic |
Feb 24 2024, 11:30 AM
Post
#16
|
Senior Member Group: Members Posts: 1,169 Joined: 23-July 15 From: New Mexico Member No.: 18,984 Region Association: None |
Why is there no rock behind the back tire?
|
Montreal914 |
Feb 24 2024, 11:39 AM
Post
#17
|
Senior Member Group: Members Posts: 1,572 Joined: 8-August 10 From: Claremont, CA Member No.: 12,023 Region Association: Southern California |
|
Superhawk996 |
Feb 24 2024, 12:03 PM
Post
#18
|
914 Guru Group: Members Posts: 5,878 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
347... Diode explanation on YouTube. 89 Nice video. Way to simple of an explanation. I would have just said (IMG:style_emoticons/default/blink.gif) |
87m491 |
Feb 24 2024, 02:16 PM
Post
#19
|
Member Group: Members Posts: 275 Joined: 29-July 12 From: Portland, the original! Member No.: 14,731 Region Association: North East States |
|
windforfun |
Feb 24 2024, 05:52 PM
Post
#20
|
Senior Member Group: Members Posts: 1,823 Joined: 17-December 07 From: Blackhawk, CA Member No.: 8,476 Region Association: None |
Gorgeous. Stunning. If that's a F40, my neighbor had one. His was white. I tried to buy one once, but the guy didn't accept my offer of 250,000 pesos. So George, when are you going to buy a decent car? (IMG:style_emoticons/default/wub.gif) (IMG:style_emoticons/default/wub.gif) (IMG:style_emoticons/default/wub.gif) |
Lo-Fi Version | Time is now: 2nd June 2024 - 01:07 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |