A/C delay timer unit

[piter]

Hi!

I've got 87 EDM Prelude with B20A1 engine and have question regarding delay timer unit in A/C system. This is exactly the same device used in Accord and it's normally bolted to the bottom side of the blower.

http://imageshack.us/scaled/thumb/266/6bto.jpg (http://imageshack.us/photo/my-images/266/6bto.jpg/)

I'm not sure what does this device exactly do. Regarding to wiring diagram It's connected both to A/C diodes and compressor clutch relay, but there's no information how does it work.

Any help?

Regards,
Peter

[Jafir]

There is some info in the ETM. It appears that all it does is put a .5 second delay before the compressor clutch engages, to allow time for the idle control system to be ready for the load from the compressor.

[lostforawhile]

There is some info in the ETM. It appears that all it does is put a .5 second delay before the compressor clutch engages, to allow time for the idle control system to be ready for the load from the compressor.the one in the accord is also a rev limiter for the compressor, it reads rpm through the same tach wire as the tach, the compressor has a lower redline then the engine, so it disengages the compressor clutch in an overrev condition

[piter]

Ok. Thanks for the answers. Especially it is interesting with these rpm. It isn't covered by the manual.So now I have explanation what for is the blue wire connected to ignition coil on accord wiring diagram.

Unfortunately Prelude harness lacks this particular connection . :/

Now I wonder is it worth to add this connection to the system. Do you know by chance what is max rpm limit for AC compressor? Just to not to overrev it now...

[lostforawhile]

Ok. Thanks for the answers. Especially it is interesting with these rpm. It isn't covered by the manual.So now I have explanation what for is the blue wire connected to ignition coil on accord wiring diagram.

Unfortunately Prelude harness lacks this particular connection . :/

Now I wonder is it worth to add this connection to the system. Do you know by chance what is max rpm limit for AC compressor? Just to not to overrev it now...

i'm not sure if the prelude uses the same compressor. if you pull an accord one and it's pigtail it's very easy to hook up, I can scan the wiring diagram if you want

[Jafir]

i'm not sure if the prelude uses the same compressor. if you pull an accord one and it's pigtail it's very easy to hook up, I can scan the wiring diagram if you want

Every 83-87 prelude I've ever seen had a keihin compressor. Accords either had keihin, or the better ND compressor.

[lostforawhile]

Every 83-87 prelude I've ever seen had a keihin compressor. Accords either had keihin, or the better ND compressor.
maby the rev limiting feature was a design improvement in the Accord, you'll see that a tach wires goes directly to the module. I'm not sure at what RPM it disconnects the compressor clutch though, I will try to hunt down where I read about the rev limit, I believe it was either in my factory service manual or my electrical troubleshooting manual

[Jafir]

maby the rev limiting feature was a design improvement in the Accord, you'll see that a tach wires goes directly to the module. I'm not sure at what RPM it disconnects the compressor clutch though, I will try to hunt down where I read about the rev limit, I believe it was either in my factory service manual or my electrical troubleshooting manual

The compressor over rev protection is on the wiring diagram in my 1987 Accord manual, but it doesn't go into details as to what the limit is.

I don't have a prelude manual.

[piter]

Most of you have seen USDM Preludes with either A20A4 or ET engines. There was used Keihin compressor. My Prelude has B20A1 engine which is european variation of JDM B20A Goldtop and shares the same AC compressor as JDM - Denso 10P15C. It was also found in CA5 with B20A2 and B20A8 engines. That's the difference ;)

However, besides this single wire, all AC diagram is precisely the same as in Accord CA5. I've spent some time studying and comparing it. Even components like relay, diodes, delay timer are the same and wired in exactly same way. The one and only difference is missing blue cable. You may be right, that since Accord is a little bit "younger" construction it might have been kind of improvement in DTU, but my DTU also comes from Accord (AC wasn't originally installed when car left factory, I've completed parts and installed it recently) and I think that simply conecting this empty pin to tacho cable should do the trick.

[Dr_Snooz]

The A/C delay is only on carbureted cars.

[Jafir]

The A/C delay is only on carbureted cars.

Look under your blower. LXi have this delay box too.

[Dr_Snooz]

The Honda manual doesn't agree with you.

[lostforawhile]

mine shows it on lxi

[Jafir]

Looks like 86, 87, and 88 Accords with FI have it, and for some reason they didn't think it was needed anymore on the 1989. Perhaps after they added IACV on the 1988, with real world experience they decided that it wasn't needed on the 1989. Just a thought.

[Dr_Snooz]

^^^ Sounds good to me.