| Author | Message | ||
| Jim Wilkerson (Wagwar)
Registered Member Username: Wagwar Post Number: 156 Registered: 12-2009 Posted From: 69.152.169.247 Rating: N/A |
My MC9 has the DD 6V92T and Allison HT 740. I recently had jakes installed and they work when tested in the driveway by applying 24vdc to the solenoids, but do not engage when driving. I've tested the wiring and switch and that is correct. I tested the wiring and switch by bypassing the lockout port switch. When I press the fuel switch, I can hear the solenoids click. So, the problme seems to be in the lockout port switch (which is new) or the adjustment of the fuel switch. The mechanic said there were two ports on the underside of the trans near the bell housing and he wasn't sure which one was the lockout port. Can anyone describe specifically where the correct port is for the lockout switch on the Allison HT 740? Thanks. | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1224 Registered: 8-2006 Posted From: 99.62.10.104 Rating: N/A |
Jim, It sounds like a test drive with the trans switch bypassed is in order. If the trans switch is the culprit, the Jakes will work when you decelerate. If they don't work, the fuel (aka buffer) switch is not properly adjusted. Jakes can only work when the engine is being turned by the driveline at a speed higher than the governor setting. At this point, the governor has the fuel rack in the no-fuel position, which the fuel switch is supposed to feel. The throttle linkage to the trans may be slightly out of adjustment also, where the trans thinks the throttle is slightly open, when actually it isn't. Anyhow, with the trans switch jumpered, and the dash switch off, take it out and wind it up to about 50 mph in 4th, take your foot off the throttle and turn on the switch. If the Jakes come on, its your trans switch and/or linkage adjustment. If they don't, its the fuel switch. HTH, G | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1098 Registered: 8-2006 Posted From: 74.33.51.199 Rating: N/A |
Are you asking for the location of the ports for the converter lock up like fire trucks use to run the PTO ? You don't need a lockout on a 740 HT for Jakes to work if you missed the o-rings on the oil jumper lines or have the wrong bolts it is not going to work be extra careful with adjusting the buffer 1/4 of a turn will send the DD in orbit. You make the Jakes hot and speed the engine up to 1500 rpm and let the rpm drop you should hear the Jakes if you have oil pressure good luck (Message edited by luvrbus on May 02, 2011) (Message edited by luvrbus on May 02, 2011) | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 497 Registered: 3-2006 Posted From: 216.198.139.38  Rating: N/A |
Jim I emailed you a diagram of the location of the ports. Hope you got it okay and can understand it. It isn't as clear as most from Allison. Bill |